£3.33!!! 3.. . . gimafln. . 11...... .51.. paltry-:1.- 111.311....) .t'hlt}:vt..u. 15.11!!!) it‘linll .. 211...}... 111‘): Ignixixll .ibtllrrzlpaxl a. Itzrrvll.n..l.il.i.. . .iluli’l‘lufrln. (ca-"wail. 11.12.... .3}. .L... .h. . 4, 1-3.35.8 , . . it}... ..(u....§?.l.llu-..tl J \..u,...l.:slu. .. . .. . ‘35.. x 1......) ”Whaling... i .1 s a . . x. . , till. Rm... fugizgliflzflaflf . . .f‘ x \l Cr. . , 8.4.5.1.! H as," 111111111qu: 31293 10714 2501 A! MERIQATION OF CERTAII PESEAI. PROPERTIES 0? 1101mm AHALGAH By Mary Jo Boehn 1'1 THESIS Submitted to the School of Graduate Studies of Michigan State College of lgriculture and Lpplied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1955 ACKNOWLMENT The author wishes to express her sincere appreciation to Professor )4. '1‘. Rogers for his guidance and assistance throughout the course of this work, and to the Office of Naval Research for a grant which partially subsidized this research. A W *1!- 1!- VRA Mary Jo Boehm candidate for the degree of Doctor of Philosophy Oral Exaination, September 20, 19511 , 2:00 PM. , Room 200, Kedsie Chemical Laboratory Dissertation: An Investigation of Certain Physical Properties of Armonimn Amalgam Outline of Graduate Studies! Major subject: Physical Chemistry Minor subjects! Inorganic Chemistry, Mathematics Biographical Items 8 Born, June 10, 1927 , Columbus, Ohio Undergraduate Studies, Bowling Green State University, 19h5-b9 Graduate Studies, Michigan State College, 19h9-Sh Experiences Teaching assistant, Bowling Green State University, 19h8-h9; Graduate Teaching Lssistant, Michigan State College, 19h9-52; continued 195b, Graduate Research Assistant, Michigan State College, 1952-1953. Member of Lmerican Chemical Society, Pi Mu Epsilon, Sigma Pi Sigma, Society of the Sigma Xi. iii 33m new of the physics}. sud chatted properties of monies assign hm been reported to he coupes-able to the properties of the alkali metal allele-s; sltlnugh the exact tumor in which nitrogen, hydrogen, at! mercury are combined in amnion esolgm is unknown. It has been suggested that mains assign, analogous to the alkali metal amalgam, is either e compound or the ”monies” radical with sorcery, or s solu- tion or such a compound in mercury. Other evidence indicates that the uslgss may be a stable froth which floats on mercury. To gain further information about the nature of the substance the magnetic properties, the solid-liquid equilibria, the behavior of an electrode, and the cmpressibility of ammonium amalgam were studied. Following an investigation of several mctlnde for preparing and handling monim nelson, an electrolytic preparation was adopted, and a means for purifying and manipulating the analgesic st temperatures in the vicinity a: 40°C was devised. .eid extraction or the manic from the decomposing amalgan provided a means for analyzing smples of the aelgan. In most cases the melgems on which measurements were made contsined less than 0.5-3 mole per cent of momma. Magnetic susceptibility measurements by the Couy method at -30°C gave evidence that «mania and hydrogen were combined with mercury in a view which decreased the freedom of electrons in mercury. Values as large as .0370 1; 10's c.g.s.units/gm. were observed for the specific suscepti- bnity of the amalgm as compared. to «0.167 x 10’5 o,g,a,un1ts/gn, for iv the speoitio suueptibility of my. the large increase in the diusnetissofsmuryto shiohonly soul]. mate: anemic: hedbeen sided ssthlishsd that “combined 1"!“ radicals oonpsrsble to slheli nets]. stone fies-s not preesnt in the mslgsn. Appmntly the assign is so entity of the type with; in which the few eloctrons furnished by “onion to mercury suffice to remove the temperature independent pers- negnsti- of mercury. Failure to tind e relationship between the conpov- sition end the density of the ssolgm suggests that the amalgam is putislly decmposed st - °C and contains mania and hydrogen gases entrapped in the mercury as well as some monies: in solution in, or in costinetion with mercury. The mslgac ordincrily studied thus appears to be e mixture containing gaseous decomposition products. A study of the solid—liquid equilibric in the system ammoniu- norcury showed that about 60% of the ammonia end manger: present in the mercury were released during a single freezing and that the decomposition produced by additional freesings was insignificant, although an appreci- able quantity of monim remained in the mercury. This indicated that some monies and hydrogen are very loosely bound to mercury in the amalgam perhaps as entrapped gas and that the remainder is present as monium or a compound of mercury with ammonium. The aeolgsm or possibly a stable froth containing the amalgam floats on top of mercury as indi- cated from cooling curves obtained simultaneously for each phase of the smslgm in which the cooling curve of the lower phase was not signifi- cantly different from that of pure mercury . From the cooling curves it was observed that during the solidification process the tempera-two of “Winn-u“! Ingmyperhlpl ll amtofmhreekinge! “I type a: bond between the deepen-Me of the mm. Definite free:- is: inseam-en Im not chum tro: the dueling owe for the “can, although the shape of the cum. we. reminiscent of "lid lulu- em “martian. It the “true” antigen cadet: u e colloid-1 dispersion or e truth at acacia-1 particles in mercury than the framing cums would be reasonable since only the mercury would mete at 40°C; the M1611 point of the analgm would be higher than 440°C. Amine! malgm electrodes were found to be largely irreversible in aqueous ethanol solution at - °c, although a value of 1.57 van- for the potential of an amalgam electrode in solution with monim ions was computed. Only in vary dilute Iolutione immediately after connecting the potentiometer does one observe e,n.r. values approximat- ing thaea for the alkali metal amalgam. Coma-9331131113.? measurements were made on samples of the malga. These indicated that the amalgam contained main, which use liquefied during oompreeaien, a: well an monim, in solution with mercury or in combination with mercury. F————————-fi rmmorcom-ms Page I. INTRODUCTION................................................ 1 II. msroaxcn 3mm: 3 mm“ AmalngOCIOIDOOOOG D. 0..ICOIUIO...OOOIIOIIOQCIO 3 Ammonium Radical. in Liquid humonia 1h Alkyl-Subotitutod Ammonium Amalgamo...................... 16 III, THE PREPARATION OF MONIUH MALGAM”....................... 17 Introduction............................................. 17 Preparation from Sodium Amalgam.......................... 17 Electrolytic Preparation................................. 19 Apparatus............................................. 19 Procedure............................................. 21 Iv. ANALYSIS OF Ammonium WMAM 25 Introduction........ . 25 ExperimentalProcedure................................... 26 v, m INVESI'IGATION or THE. MAGNETIC PROPERTIES OF AMMONIUM mom AND OF MERCURY 28 Introduction.......... .......................... 28 The Nature of Alkali Metal Amalgaxns................... 28 The Magnetic Properties of Amalganc................... 29 The Magnetic Properties of Mercury.,.................. 31 Theoretical Discussion.......... . ................ 32 The Magnetic Susceptibility Moacuromente................. 35 Ipporatus”........................................... 35 Ebcperimental Procedure........ ................. 37 The Magnetic Susceptibility of Mercury at Low Temperatures.......... ...... 38 The Ha tic Susceptibility of munonium unalgam at - ee-ueuoooo-ee-ocoon-oeovoooo-enopoaooo-o-oeno 112 Discussion of Results 1&3 VI, SOLID-LIQUID EQUILIBRIJ. IN THE SYSTEM iM’IONIUM—MI‘RCURY....H 52 Theoretical IntmduCtionc-ou.o‘ooceooaoo-onoeeoe-aneao-eo 52 Historical Summary... 55 Introduction to Experimental Procedure................... 55 vii rm (1’ comma . Continued Page Apparatus tor Recording Cooling and Warning Curvel....... 5? Cooling and Warning Curve. for Each of the Tao Phone: of mmag”....OOQOIDCOOOOIOOUIUIOOOI'OOIOOOOOC'ODD‘OOI 6° Exocrinentfl Procedure.... .. 60 Reeulte and Diecueeion....... .. ...... . 65 Cooling and Warming Curves Obtained During Agitation of Eugene-ocean” eoeeeeoceeee-e-eee-o-eeeeeeoeeo-onee 71 Experimental Procedure................................ 71 Results and Diecueeion..... ..... ........... 75 Cooling and Warming Curves Obtained 'While Ammonium Amalgam we; Decomposing in a Closed System............ 76 Experimental Procedure................................ 76 Results and Discussion................................ 83 Conclusions.............................................. 9b VII. CERTAIH OBSERVATIONS OF THE BEHAVIOR OF AMMONIUM AMALGAM ELmTRODESOQOIOIO.OOOOI0.00‘Cf'0.‘9...O‘CCOOOOCICOCCCIIOQQI. 96 Historical Introduction........ . ...,... 96 The Effect of Ammonium Concentration on Electrode Potential.......... .............. 100 A Concentration Cell with Ammonium Amalgam °Electrodes.... 106 VIII. COMPRESSIBILITY OF AMMONIUM AMALGAM AT -300 C................ 112 Theoretical Introduction................................. 112 Appa‘atuafiODIOCDDO'.Ilthll.DIIOOOOCOCOIOOOCOODIOOOIOOQOCO 111‘ Experimental Procedure...” ...... 117 Calculations and Results 120 Discussion............................................... 128 eroeueevoeee aaaaaa coco-ene'eeoeeeeeeeeo-eoeoovoeeone-o-oeeee 133 IJTERATURE CITED..........u....................u.............a. 136 viii cm: I I II. XIII. XIV. LIB! OF TABLES Page Calibration at the Field Strength of the Beetronagnet... ho Magnetic Susceptibility Tube Corrections at Various Tampuatm'lO...0IO.IO.‘C...O0...IOU-OIIIIOICQICDCOOOOOO he The Magnetic Susceptibility of Mercury at Various TwperamaOIOO‘IIlI.CIIIIOOODIOIDIODDOOOOOCIIOOUOOIUUO. u The Specific Magnetic Sueceptibilitiee and Densities of mum 31118ng1)! at -300c.-.loa uguesoeoeooso-osoocooc-u- uh Compositions of Amalgems................................. ’45 The Relationship Between Density-Composition Data of Ammonimn Amalgam”....................................... ’46 The Molar Susceptibility of Ammnitm in Ammonium Amalgam. SO Depression of the Freezing Point of Mercury by Amonimn... 56 Calibration of the Volume of the Closed System. . . . .. . . . .. 81 Measurement of the Decomposition of Amelgame During Freezing and Melting..................................... 8h The Change in Composition of Amnonium Amalgam on FreezingOCIDOOOICIOODIOOIIIOIICIIOIOOIOOOOOODOIOIIUUOOOCI 86 Potentials of the Alkali Metal Amelgems in Aqueous $1utinn..l.1IOOUIOIIII‘O..I....CIODOUOCOCCCIDO'ODOCDCC‘. 99 mectrmotive Force-Concentration Date for Amonimn malga‘ns at -3OOC-ocoosloooilu0.0.00.tracts-OIOIIIOIIOIDO 105 Data for Two Concentration Cells with Ammonium Amalgan Electrodes at -300L 109 Pressure-Volume Data for a Compressibility Study of Amonium Amalgan......................................... 121 ix 3.18! w 1131.38 - Continued Page XVI. ammunition of Amalgam for Which Compressibility Data “r. atmd..'ICOCOOIOOO.OOOIOCOCOOCOII....I‘C'OOODIUIOO 12h XVII. A Comparison of the Volumes of Armenia, Wagon, and Hercury with the Volume of Amonium Amelgm............... 126 XVIII.~ Volume Occupied by Gaseous Amonie and Hydrogen in Each Anal-gm at - filo-IoneooooooouIce-eooeoos'eovooOil-scoo- m. The Density of Amonimn Amalgane Corrected for the Presence of Gaseous Decomposition Products . . . . . . . . . . . . . . . . 132 LIST a FIGURES 2mm Page 1. Schematic diagram for a constant current power supply..... 20 2. Cell for the electrolytic preparation 01‘ monim melgun. 22 3. The Gouy magnetic balance................................. 33 h. Apparatus for measurement of magnetic susceptibilities st lowtemperatures.......................................... 36 S. Gran-susceptibility - density data for monimn amalgam at -3 one.ousosoooeseosooseoassess-oosooooo-oocloseness-sec he 6. Certain typical composition - temperature diagrams for a hue-component system Sh 7. Schematic diagram for recording cooling curves. .. .. .... S9 8. Freezing tube and jacket for studying the freezing process inatm.phm systemOI.OOOIOIIOOOOIIOODDOOOOII'OOIICOOOI. 63 9, Cooling curves procured simultaneously for each of the two phases of an analgan...................................... 66 10. Warning curves procured simultaneously for each of the two phases of an amalgam... 6? ll. Successive cooling and manning curves procured simul- taneously for each of the two phases of an smalgsn........ 68 12. Successive cooling and warming curves procured simultan- eously for each of the two phases of an smalgsm........... 69 13. Fluore thene freezing tube and jacket for studying the freezing process during agitation of an amalgam . . . . . . . . . . 72 1h. Successive cooling curves procured while an analgem was being agitated-0....l0.l'lO...IIOIIOOOOOO¢IIUOUOOCOOIOOOOI 73 15. Successive warming curves procured while an amalgam was being agitated...OIIlOCOIIDII00.OOOUIIQQOIQIIOOOIOD'UCI... 7h use (I nuance a» Continued Page 16. Apparatus for measuring the volume of gas evolved from on ”alga dmng Imumglcoesoot-soooleI-onosnsout-Isoo-os. 77 11. Pyrex tube and Jacket for freezing an melgm in a closed C...IOCOCCIOOOOCIICOIOOOOOIIICUOOIIIIIlIQ.OI'.l..|IO 78 18. First successive cooling and Wing curves obtained for an “818” in a. @1088‘1 ”stale.ssoalcuocscaosootcosoucsooc 8? 19. Successive cooling curves obtained for an amalgam in a closed .y’tm.OD.OI.ICIOIIIOOOUO‘COOIOOOOCCI...IIIICOOIIIC 88 20. Successive naming curves obtained for an amalgam in a closed system 89 21. First successive cooling and warming curves obtained for an amalgam in a closed system............................. 90 22. Cell for measuring the e.m.f.'s of amalgams containing varying concentrations of ammonium with respect to 3 “mm elecltrodGOOIOO..D¢'.OOOOI.CDOOOIOUO‘IIIOOUOOICOOOI 102 23, The variation of e.m.f . with time for cells with axmnonim amalgam electrodes........................................ 103 2h. Concentration cell with amonium amalgan electrodes..... .. 107 25. Apparatus for studying the compressibility of ammonium malgMD'IQJ‘IQUOOI.0....IOIGCOOCDOODOIOCCOOOI.IQQCOII.~O' 115 26. Volume-pressure data for ammonium analgam at ~30°C.....,_. 122 27. Acomparison of the pressm'e-volme data for an amalgam at -3000 with the ideal behavior of a mixture of mania and fwdl‘ogen 8t -300.C........... soon-sosoe-ssso-o one as £100.00. 12? I . WING?!“ The out manner in which ammonium is combined with mercury in mains: snags: has not been characterized, although many investiga- tions of the physical and chemical properties of the amalgam have been undertaken in the past 150 years. Il'he true nature of the malgsn has been somewhat masked by its tendency to decompose into mania, hydrogen, and mercury at all temperatures above its freezing point, which is approximately -hO°C3 however, temperatures below -20°C inhibit the de- composition of dilute amalgams appreciably. A comparison of the properties of ammonium amalgan with those of the alkali metal malgams suggests that the ammonimn radical is bound in some way with mercury. Magnetic susceptibility studies of the dilute alkali metal analgams show that small quantities of solute vary the dia- magnetiu of mercury and that compound formation takes place at relatively low concentrations of alkali metal. An analogous study was expected to clarify the nature of ammonium amalgam, so that the purpose of this investigation was to study the magnetic properties of monium amalgam at temperatures sufficiently low to minimize decomposition. If ammonium dissolves in mercury as a neutral species the malgam should be strongly paramagnetic due to the uncompensated spin of the unpaired electron, but it ammonium is ionized in mercury the diamagnetiam will be increased by the contribution of an additional atomic core, .1- supplementary investigations or the fleecing process, the deeonpo-v titles on fleecing, the behavior of “9111111! malgm electrodes, and the compressibility were carried out in order to gain further intonation shout the state of monium in the amalgam -2- -....-I- _ . . . 11. WA}. snow Amenitm Amalgam Ameniim malgsn has been the subject of many unusual enmeriments tree the time that Seebeokl reported the formation of the substance dur— ing electrolysis of moistened amonim carbonate in contact with mercury. Seebeck's finding in 1808 in Jena was simultaneous with the announcement of Bersslius and Pontin in Stockholm that a soft solid less dense than mercury was produced in the electrolysis of masonic solution nth a mercury cathode. Berzelius and Pontin comunicated their discovery to Sir Emphrey Davyz explaining that osmosis like potash and soda was an oxide, the metallic part of which combined with mercury to form an uslgam. Only a short time previously Davy had isolated sodium and potassium and learned of their vigorous exothermic reaction with mercury; therefore, he immediately began experimenting with amonimu amalgam Be prepared hollowed-out blocks of momma chloride and monium carbonate which he moistened and filled with mercury. The block of salt rested on a platinum strip joined to the positive electrode of a battery while the mercury pool was joined to the negative pole through a platimmx wire. During electrolysis an amalgam of very low density formed and a black deposit was observed on the surface winch Davy thought to be a residue of carbonaceous matter from the decomposition of carbonate. Be prepared somewhat less pure amalgams by the reaction of monimn salts with mercury solutions of alkali and alkaline-earth metals. He attempted -3- meeut‘ally to preserve staples of the maize: but was able to da— terline the specific gravity as being less than three. Davy was puzzled that upon decomposition of the amalgam he was unable to form the oxide of monia comparable to potash and soda, the "comics" of potassium md sodium 1b proposed that “deoménatod” ammonim was present in mercury ”in the nascent state, or at least in that condensed form in which it exists in maniacal salts, or solutions." Later Dewy3 concluded that monium and mercury form a compoxmd. Gay-Lussac and Thénardh regarded ammonium amalgam as a compound of mdrogon, nitrogen, and mercury on the basis or their experiments which indicated that the ratio of anmonia to hydrogen in the amalgam was 2.521 by volume. That monium is a radical which behaves like a metallic substance was first proposed in 1816 by unpere5 whose theory was elaborated by Berselius and was generally accepted as explaining the composition of monium salts, but various theories arose concerning the amalgam. Daniel].6 believed that mercury absorbed amnonia and hydrogen in the way that silver absorbed oxygen. Grove7 electrolyzed moonimn chloride solu- tion with cathodes of zinc, cadmium, copper, silver, and gold in an attempt to find a reaction of ammonium clfloride with other metals com- parable to the reaction with mercury. During the electrolyses dark- colored and sometimes spongy deposits formed from which mania was never observed to be released, although possibly nitrogen and hydrogen were, according to Grove. Eh interpreted the results to mean that ammonimn also reacted with mercury to form a nitrogenwmercury compound -1;- interspersed with hydrogen which was responsible for the swelling appar— ent in amenim malgau. IRho volme ratio of mania to hydrogen in an amalgam ample as dotemined by Iosndolt8 was 2.15-2 .1; to l, a result considered inconclu- sive by Routledge ,9 who devised an apparatus simila- to a gas burette that provided a means for measuring the total volume of gas released from a decomposing amalgam. The ammonia was absorbed in acid dropped into the apparatus and the volume which remained represented the volume or Wogen. The results of four experiments gave values between 1.98 and 1.93 for the volume of anmonia per volume of hydrogen. Seeley10 reported in 1870 that the volume of ammonium amalgam varied according to Boyle's law when pressure was applied to an amalgam sample by means of a plunger in a glass tube. Routledge, in a more thorough compressibility study, subjected a supple in a glass tube to various pressures through the use of a syringe. The pressure was measured with a manometer and the volume was determined from the change in level of the sample as pressure was applied. Routledge studied the compressibility of electrolytically pre- pared melgama and found that at room temperature the amalgam was slightly less compressible than expected for a mixture of ammonia and hydrogen under the same conditions. Routledge concluded that the amalgam was a compound of ammonimu and mercury which decomposed readily into ammonia, hydrogen and mercury. His publication contained a complete historical review on monium amalgam up to 1872. LeBlancll measured the polarization, relative to an amalgamated zinc electrode, of a series of. alkali and alkaline earth anelgaus prepared -5- electrolytically tron their salt solutions. rho polarisation ct these aligns was about one volt water than that observed in the electroly- sis o! hydrochloric acid solution with the amalgamated zinc electrode, and was the some as the value measured for ammonium magma. LeBlanc concluded that in monitor amalgam a metallic substance comparable to Iodine and potassium was combined with the mercury. It in the electroly~ sis of monim analgsm the polarization had corresponded with that of maroohlorio acid then the polarisation could have been attributed to the discharge or hydrogen ions, since ammonia was not an ion. Coehn and Dennenberg12 measured the depolarization in electrolyses of alkali metal and monim salt solutions with a mercury cathode. The decomposition potential for hydrogen at the mercury cathode is 1.52 volts, but as a result of the formation of amalgam the deocxnpoaition potential in the presence of alkali metal ions is lowered by an amount dependent upon the particular metal ion. In the presence of amonim ion lvdrogen is evolved continuously from the mercury cathode at 1.21; volts which is entirely comparable to the value for potassium and gives further indication that monium amalgam is similar to alkali metal amalgam. Coehn13 repeated part of Lendolt's work on the displacement of ions from solution by muonimn amalgam. If the temperature was as low as 0°C, copper, cathnimu, and zinc were displaced from sulfate solu- tions by the amalgam; otherwise, the radical decomposed before reaction took place. Coehn's results suggested that ammonium amalgan is a good reducing agent, and we know now that even the alkali metal ions can be displaced from solution in the presence of mercury, -6- 1!! 190! Henri Rois-mu Wished the results or his experiments an “onion malgn. lie treated a solution of mania: iodide is licuid ms with sodim ensign to make an monimu amalgam which was more fluid than scum malgam and which did not evolve gas. Purification consisted of rinsing with masonic and decanting the iodide solution. Hoissen cooled the smalgan to -80°C veshed it with other at ~3o°c and placed it under reduced pressure under which conditions no gas was evolved. As the temperature rose above --80°C the amalgam decomposed slowly with a noticeable volmne increase appearing at ~30°C and a volume increase or 25 to 30 times the original at +15%, In all the experiments the temperature of the amalgam during decomposition was 5 to 6 degrees above the temperature or the surroundings. The decomposition proceeded for 12 to 15 hours in some cases but could be enhanced by naming. If the malgm was washed with an acid instead of. ether at ~80°C some decomposition took place at the lower temperature, but the ratio of ammonia to hydrogen evolved was always 1.99 to 1. For analyzing the decomposing amalgam, mmonie was collected in water and the hydrogen volume measured in a eudiometer. Moissan did not feel that his results showed that the monium radical endsted in mercury but that actually the amelgan was an ”moniecal metallic hydride." He based his decision on an analog with sodium analgem which if placed in liquid mania slowly released hydrogen with no change in volume, but addition of sodium hydride to the solution expanded the volume of the sodium amalgam for two or three days. .7- lush and trusts” utilised Romeo's method t6 prepare monies assigns for s series of freezing point deteminstions in an sttemt to 1am whether th aalgm was a true solution or an emulsion of masonic, hydrogen and mercury. A conventibnal type of apparatus used in freezing point measurements for molecular weight determinations was employed, I slang dth a platinum resistance thermometer. The monium amalgam were oxmhed for sodium content but no mention was made of the analyti- cal method used. The wonimn concentration was determined by titration with standard acid following the freezing process. Amalgam with con- centrations of amenimn between 0.1 and 5 atom per cent were frozen by means of an alcohol bath maintained at temperatures 5 or 10 degrees below the freezing point of mercury. The freezing point depression per mole of mania was calculated to be about 112 degrees for four of seven solutions and approzdmetely half that value for the more concentrated solutions. Rich and Travers decided that monium malgan was a solution of NH‘ in mercury, but Smith“J in 1907 showed that flair conclusion was not the only one which suited the data. Smith demonstrated that if the ‘ solute were assumed to be a compound, 9.3., mung”, in which one mom is combined; with many atoms of mercury the same freezing point depression would apply. Smith prepared ammonium amalgam by electrolysis at 0°C and washed the amalgam several times in ice water. & poured samples” of the amalgam into potassium chloride, potassium hydroxide, barium chloride, and barium hydroxide solutions and washed the amalgam by decantation until negative tests for potassium and barium were obtained. Upon extraction of the resulting analgams with hydrochloric -8... said In snalysie ehoved that main ions had displaced barium and petunia ion: from solution. filith felt that this interchange of ions proved the nelgn to be a true compound of HE‘ and mercury in solution with Ieroury. {hith's disagreement with Rich and Travere' work and the Merity of his experiments and conclusion: with those of Coehnu brought criticism from both comes and produced two publications by 3.1149849 in his own defense, but no additional experimental results. Perhaps it was to be expected that following the turn or the century when the phenomenon of radioactivity was not completely understood, that an unstable substance such as amonimn amalgam should be examined for radioactive coutent. In 1906 Baborovslqy and Vojtechao prepared ualgsm by electrolysis and also by displacement or sodium from sodium amalgam. They placed silver bromide gelatine plates 3 cm. from decomposing amelgems for several hours, but the photographic emulsion remained un- exposed; therefore, any "rays" emitted from the substance were apparently not of radioactive origin. In another experiment Coehn21 found that monimn analgem discharged a negatively charged electroecope. About this time organic derivatives of anmonium chloride were found to yield 2 the corresponding amalgams by electrolysis,2 and the properties of certain of these, e.g. methylanmaonium amalgam and tetranethylanmonium enalgan, were being investigated. McCoy and West23 reported that tetra— methylammonim amalgam, which can be isolated from mercury in the form of crystals, rapidly discharged a positively charged electroscope, while amonimn and monomethylanmonium amalgam discharged the electroscope ~9- leg-rune or whether the charge was positive or negative. However, mania nalga discharged a negatively charged lost 20 to 50 than more rapidly than a positively charged leaf. Radioactivity was ruled out as the cause of the ionisation effect of amalgam because the rate of discharge was not constant and varied with the sign of the charge on the gold leaf. Following a series of investigations as to the effect or temperature and exposure to ultraviolet light on the decomposition of tstranethylamonitm amalgam, McCoy and West concluded that the gas particles become electrified upon bubbling through the surface of mercury. Lennard.2h had slam in 1892 that bubbles of gas passing through mercury actually gain a potential which may be either positive or negative depend— ing on the particular gas. hronheim"e5 made a more exhaustive study of the ionization properties of decomposing monium amalgam in which he plotted many timenversus-electroecope deflection curves at various temperatures. These plots approndnated straight lines up to a madman potential which was dependent on the temperature of the amalgam. The data were those anticipated if the ionization was a result of the "Lennard effect." In 1928 Sender and Ki’ochsche26 exposed monium, sodium, and potassium amalgam to light of various wave-lengths and measured the photoelectric emission produced by each amalgam. The electrometer in the photosensitive circuit registered deflections wlnn light of wave-lengths between 1000 and 1500 A0. irradiated an anunonimn amalgam ample. The long wave- length limit for sodium amalgam was 11950 A0. and for potassium was ~10- mt higher although the exact value was not obtained. Pros these data it can be concluded that the monium radical has a higher electron affinity than sodim or potassium. Ilden Dcympfl studied the rate of decomposition of monixm analgsm ct ~20°C and 00°C. Be prepared amalgam by electrolysis of aqueous uranium acetate saturated with amonia gas at —38°C. The mercury cathode was kept partially frozen and was stirred. Following their preparation the analgesic were stored at -78°C. I; frozen amalgam was placed in a hydrogen-nitrogen atmosphere and warmed to the temperature of the de- composition study. [an amalgam ample was removed periodically for analy— sis. Although Deyrup observed that freezing partially decomposed the amalgan, he froze the samples taken from the reaction vessel to preserve than before analyzing the ammonium content by reduction of iodate ion. The velocity constants for the decomposition of several amalgams at -20°C and - 0°C agreed very precisely, and the Idnetics appeared to be representative of an sutocatalytic reaction. The decomposition became a second order reaction following the addition of lithium metal to the amalgam. Deyrup proposed that two decoxnposition reactions took place, a heterogeneous reaction at the surface between the amalgam and bubbles of reaction products, and a homogeneous reaction as a result of collision between two ammonium ions and two electrons. The racial freezing point depression constant use determined to be 51°, but no experimental data were listed. Lt pressures between 30 and 600 atmospheres the potential of almonimn analgam was measured with respect to a, reference electrode of -11- Mi)/la3r.(o),la.ar(aq) at o°c by Nirmfibe and mutiny.” nu 3'.ng was prepared by electrolysis or mains bromide solution in a cell enclosed in e. procure chamber. The electrolysis was discontinued every forty seconds for an 8.1!.1. measurement. High preenn-e decreased the rate of decomposition and stabilised the cell potential to some extent; however, the eJnJ. dropped by 1.316 7. after 140 minutes at 30 atmospheres, and by 0.71:6 v. after he minutes at 600 atmospheres. The potential varied with the concentration of amonium bromide, but not ydth pH, and boosts lees negative with pressure, A plot of E3, the cell potential with respect to the hydrogen electrode, against the logarithu of the current density of the electrolysis was a straight line for each series 01‘ measurements at a constant pressure, but no value for E0 was computed, since the concentration of ammonium was unknown. The initial values observed for EH varied between 1.60 and 1.83 volts. The behavior of ammonium amalgam as a reducing agent for organic 29 who prepared compounds was widely investigated by Takaki and Ueda, amines and ,6 ~11ydroaqr1anines from nitro compounds with the analgam. They treated monium analgam with many different ketones and aldehydes and characterized a variety of products from each reaction; for example, benzaldehyde reacted with the amalgam to form benzyl alcohol, hydro- bensoin, benzylanine, ieohydrobenzoin, dibenaylamine, and mesoatilbenedi- amine. The polarographio reduction of amnenim ion to the amalgam at the dropping mercury cathode was studied in a. saturated solution of tetra- butylammonimn iodide in liquid ammonia by Laitenen and Shoemaker,30 who .12... found the believers potential of ammonium ion to lie between the values tor litbiu and sodiue. In 1951 Johnston and Ubbelohde31 studied smalgsns prepared at room temperature by electrolysis of ammonium sulfate solution between 10 and 20 millismperes. They analysed the electrolyte for ammonium released so mania and the ualgm for "latent monium' retained in the analyse. The formation of 'latont ammonium" was suppressed when the electrolysis was carried out at temperatures above 50°C, or in the presence of ammnumm sulfide which poisoned the mercury cathode. Optimum conditions for preparing ammonium amalgam corresponded well with those for preparing potassium amalgam from electrolysis of potassium sulfate. At the voltage corresponding to formation of wmnnium amalgam the surface tension of the mercury decreased appreciably. The surface viscosity at the cathode as measured with an oscillating-disc viscometer increased much more rapidly during amalgam formation with ammonium sulfate than with potassium sulfate. A phenomenon, called the “wedge effect", is evident during electrolysis in a glass column with electrolytes of alkali or alkaline earth salt solutions over a mercury cathode. The electrolyte forces itself between the glass and mercury in a wedge with the apex downward. The length of the "wedge" was dependent upon the cation, and the largest "wedge" ever obtained by Ubbelohde and Johnston was 16 cm. long when ammonium sulfate was electrolyzed under Optimum conditions for amalgam formation. The experiments show that potassium and ammonium amalgam behave similarly. The authors believe that ammonium amalgam is a froth which is stabilized by low surface tension and high surface viscosity and that -13- the rate of decomposition is less than predicted by Deyrup. the most recently published work on moniun amalgam is an array diffraction study of amalgms prepared by reaction or ammonium iodide with lung. in liquid anionic at —ho°c, and stored at 4800.32 Following their preparation the malgans were washed with liquid mania and frozen by stirring with liquid air to form powders. In three xrray powder diagrams of monim amalgam made at —190°C several intense lines appeared which were not explainable on the basis or any known impurities. Lines characteristic of Nefig‘ were absent because of excessive strains in the compound at ~190°C. Several amelgams were carefully analyzed by passing the hydrogen evolved in decomposition over heated copper oxide and observ- ing the weight change. The analyses indicated that the amalgams contained some unreacted Naflg‘ and less ammonium amalgam than should have been present had no decomposition taken place at —78°C as predicted by Deyrup. Beenziger and Nielsen believed that certain lines characteristic of the amalgam were present in the powder diagram; however, no obvious relation- ship existed between the lines which would have enabled them to predict a crystal structure for ammonium amalgam. Ammonium Radicals in Liquid Ammonia In addition to the many experiments concerning the nature of ammonium in amalgams, three investigations of the possible existence of free ammonium in liquid ammonia have been made. Otto Ruff33 in 1901 attempted to prepare free ammonium at -95°5 in a solution of potassium and ammonium iodide in liquid ammonia subjected to a pressure of 60 atmospheres. -1h- ll predicted that it free ammonia formed according to the reaction I + ELI —-> II + “3‘ the blue color characteristic of potassium in solution with liquid mania would disappear. Ruff was unsuccessful in this attempt, as was loisssn ,3h who in the same year reported that he was unable to prepare free monium by the same reaction as Ruff, under the pressure of the ataosphere. 35 repeated the experiments of Ruff In 1921 Schlubach and Ballauf and Moissan only to obtain the same negative results. Using much more dilute solutions than in previous experiments they found that when monium chloride was added to a solution of potassium in liquid ammonia and the solution was kept at -70°C for three hours the blue color dis- appeared and an amount of hydrogen, much less than that calculated if all the amonium had decomposed, was evolved. after the potassium ctfloride was filtered off, iodine, which does not react with liquid ammonia at ~70°C, was discolored by the filtrate. When the solution was flamed the remaining hydrogen was released at -hO°C. Hydrogen was found to be much less soluble in liquid mania than would have been necessary for all the hydrogen to be retained uncombined in solution. Immonium salts form colorless solutions during electrolysis in liquid mania at ~70°C as do meth salts which evolve ethane as a product when their solutions are decomposed at higher temperatures. Tetraethylammonim salts under simi- lar conditions acquire a deep blue color analogous to the alkali metals and form a series of decomposition products including triethylsmine and ethane. -15- MIL-Substituted Amonims Amalgam Two organic nalgm, nononethylmoniun ensign and tetrmthyl- ”slum analyse, have been prepared by electrolysis of the respective chlorides in alcohol solution at -1000. McCoy and Moore, who have investi- gated the properties or these smolgams, found that both are unstable shove 0°C and that the nononethylamonium amalgam was sort and had the appear- ance of ammonium amalgam, while the tetranethylsmnonim amalgam contained almost crystalline lumps and was relatively stable at temperatures around 0°C. Trimethylamine is a product in the decomposition of tetrs- ! nethylsmmonitm amalgam which might follow the reaction: 'NHe4 '_"‘> We; ‘P M3 . In 1951; Porter36 detected methyl radicals in the decomposition products of tetramethylexmnonium amalgam through the use of tellurium mirrors, using the method of Paneth. .16.. III. TE PREPARE?!“ 0! MORE)! mm Introduction Antonina malgam has been comenly prepared by two different methmis-w by electrolysis of m ammonium salt solution with a mercury cathode and by displacement of an alkali metal nelgan with ammonium ion. The choice of ammonia: salt for either preparation depends on the choice of solvent. Sodium amalgam has been almost exclusively employed for the displacement reaction. In this investigation amenium unalgam was first prepared in order to make magnetic susceptibility measurements. An malgsm free from impurities which might interfere with interpretation of the measurements or with the analysis of the malgam was desired. The amalgam had to be reasonably concentrated and in a, physical state that would permit its transfer to a, tm of 6.5 m. inside diameter. An apparently straightforward method employed by several investigators is that of i'Ioissuml’4 in which ammonium ion is reacted with sodium amalgam in liquid ammonia. For Moiseen's preparation to be satisfactory in the present work the sodium amalgam would have to be reacted completely and all sodium ions removed in the purification process. Preparation from Sodium Amalgam The first step in the preparation of monium amalgam by Moiasan's method was the synthesis of s 3 per cent sodium amalgam prepared directly -17- from seifllsd quantities of mercury and sodium.” An introductory experi- ment 'as attempted in which a piece of sodium melgas was dropped into an aqueous solution of selenim chloride in a beaker at room temperature. The sodim analgem immediately expanded into a sponge-like material and within five minutes occupied a volume more than twenty times the original. The malgn was quite black in color and sufficiently less dense than water that at one stage it floated on the solution. Decomposition of the asalgn was rapid at room temperature and appeared to be emeplete in an bur. The solution that remained above the mercury was strongly alkaline as a result of the displaced sodium. When ice water was used for msung the monim chloride solution the rate of decomposition of the malgam decreased, but not enough to make this an acceptable method of preparation. In a second attempt to prepare monium amalgam by Moiesan's method liquid asmonia was poured from a gas cylinder into a Dewar flask and sufficient anmonium chloride was added to make a, one molar solution. about 50 g. of coarsely ground sodium amalgam was added to the solution with stirring. Ho reaction was immediately apparent, but as armonium amalgan formed the consistency of the sodium amalgam became paste-dike. From the first this reaction did not appear to be rapid and even after five hours pieces of unreacted sodium amalgam remained. This procedure was followed several times but the reaction was never found to go to com- pletion. This Was shown by removing the amoonium amalgam prepared in this way from the liquid ammonia and decomposing it by warming to room temperature. When the evolution of gas from the amalgam was complete an aqueous amonium chloride solution was poured over the malgam, resulting .13- in the typical reaction of monim ion and sodiml nelgas. Later llsnsiger and sauna” reported that in their investigation mains ion failed to displace sodium from sodim malgm completely. Electrolytic Preparation Apparatus An electrolytic method was then adopted for the preparation of ammonium amalgam. A series of different electrolytes, reaction vessels, and refrigerants were investigated before a wholly satisfactory method was devised. Initially a low-voltage power supply was used for the olectrolyses; however, the current varied with the resistance of the electrolyte and the resistance changed appreciably as electrolysis pro- ceeded. Heat generated in the cell at electrolysis currents of two or three mperes enhanced decomposition of the analgam. A more satisfactory power supply was constructed according to the circuit diagram in Figure 1.38 This power supply was a constant current device with a vari- able output between 0 and 1:20 millimperes at a maximum potential of 250 volts. The current during an electrolysis with this power supply was constant to within 1.5 per cent as determined by measuring the voltage dr0p across a one ohn resistance with a. Brownvofimeywell Electronic Potentiometer. The composition of amalgame prepared by electrolysis with the constant current pomr supply could be readily adjusted by variation of the current or electrolysis time. If the amalgam was to be preserved in a relatively concentrated form for more than a few minutes the temperature had to be lower than ~10°C .0 .m mpHo> 0mm mo omepaoh Ebsfixms a pm mopoaew IHHHfiE own now 0 noozvmn oflnwwhwh mw pnmvzo esp uhflmmsm Moron penance pumpmqoo how snowman ofimeonom .H onsmfih >o: _ a $3.. + <8 >o: + <8. + 48 whine-(4: or VMQOo + (Hm)mHgn + m/2 01,. The analgn floated on t0p of the mercury cathode during the electrolysis and occasionally a black deposit appeared on the surface of the cathode in the vicinity of the anode. This deposit has been reported by many investigators in the past and was found by McCoy and Moore22 to be at least 95 per cent mercury. At the completion of electrolysis the analgan was purified inside the cold box. The mercury-rich solution was first drawn off through the -23- — stopcock of tin cell sad than the saslgsa was drained into a 1:1 aqueous alcohol wash solution, while the electrolyte was retained in the cell. filo uslgem was washed two times with aqueous alcohol by deoentetion and finally a third time in a separatory frame]. from which it was introduced into the appropriate experimental apparatus. The surface of the amalgam was then touched with absorbent tissue to remove the alcohol-mater wash solution more completely. The composition of the amalgam depended greatly on the tamerature in the cold box during the electrolysis and purifies- tion procedure, as well as on the amount of handling necessary to fill a saple tube for a particular meamxrement. ~21L- IV. amaze OF mamas W Introduction Four different analytical techniques have been employed for determin- ing the concentration of monium in the snalgam. The method of gas snelysis is dependent on the decomposition of monitm into hydrogen and mania in the volume ratio of 1 to 2, a ratio which has been well estab- lished .9 ’1“ Measurement of the combined voltnnes of mania and hydrogen or absorption of the mania and measurement of the volume of hydrogen alone is sufficient for the analysis. Analyses dependent upon the mount of mania or hydrogen released during decomposition have the disadvantage of providing a value which may include the quantity of amnesia or hydrogen entangled as gas in the malgem in addition to that present as the moniun radical. Amalgam which are to be analyzed should be kept at low tempera tures to inhibit decomposition. The most common analytical method for the determination of metals dissolved in mercury consists of extraction of tin metal with an excess of standard acid followed by titration of excess acid with standard base. Baenziger and Nielsen32 analysed the amalgam by reduction of hot capper oxide with the lwdrogen released from a decomposing amalgam. The method appeared to have the disadvantage of determining a small change in weight of a relatively heavy absorption tube. Deyrup27 used the reducing property of amnenimn to determine the composition by reduction of iodate according to the reaction -25- 68.0 . Io.‘+ an. -> em.“ +1‘ . 321,0 + cos? renaming reduction and acidification the iodine formed was distilled into potassium iodide solution and titrated with standard thiosultate. Wrinentel Procedure Several amalgam: were analyzed by measurement of the volume of hydrogen released through decomposition into a gas burette. A sample tube of amalgam at a low temperature was joined by means 'of a ground glass connection to a 10 ml. gas burette. As the amalgam warmed to room tempera- ture the evolved anunonia was dissolved by the water in the burette and the volume of gas observed was that of the hydrogen alone. Complete decomposition of the amalgam required at least an hour during which time the possibility existed that hydrogen might diffuse from the system. \ w 1 Frequently the volume of hydrogen released from an amalgam was as little as 2 ml., so that errors introduced by diffusion would be appreciable, and the method was abandoned. The analytical method adopted for the determination of ammonium was the acid extraction technique. An amalgam sample at the temperature of the physical measurement, usually ~3OOC, was quickly run into an iodine flask containing an aliquot of standard sulfuric acid. The amalgam was set aside for several hours to allow complete decomposition, after which the acid was titrated with standard sodium hydroxide using methyl-red indicator. On occasion the transfer of amalgam to the standard acid was made inside the cold box. Since this contained an essentially carbon -26.. dioxide atmosphere, particular precaution was taken to remove carbon dioxide from the acid solution. Slightly before the and point was reached in the titration with sodium hydroxide a stream of compressed air, which had been passed in succession over Ascarite and Drierite, was run into the titration flask for five minutes to remove carbon dioxide. Without this precaution the endpoint was not sharp. Following the titre- tion the water solution was decanted from the mercury remaining in the bottom of the iodine flask and the mercury was washed several times with distilled water, dried with acetone, and weighed. An approximately 0.25N stock solution of sodium hydroxide was pre- pared from sodium hydroxide pellets*and conductivity water. Barium chloride solution was added to precipitate carbonate. The sodium hydroxide was standardized against potassium hydrogen phthalate with phenolphthalein indicator.” A 0.3N sulfuric acid solution made with boiled air—free water was standardized against the standard base using methyi-red indicator. Two liters of each of the stock solutions sufficed for all the analyses. More dilute standard solutions were made from each of these stock solu- tions whenever necessary. *Baker's Analyzed Reagent C.P. sodium hydroxide. -27- V. Alw MMIGATIOII OF THE mum PROPERTIES wmm mm AND OF MERCURI Introduction The Nature of the Alkali Metal Imslgems That the alkali metals are soluble in mercury was first observed by Kerpm in 1898 , who determined the composition of certain of the solid phases and advanced the idea that definite compounds exist between mercury and the alkali metals. Smith and Bennettl‘l reported that the alkali metals form compounds with mercury which are in solution in mercury. Host investigations of the physical properties of the alkali amalgam have been directed toward learning whether the alkali metals exist as ions, atoms, or compounds in mercury. The conductivities of the anslgens have been widely investigated since Bornemerm and Muller!"2 established that the conductivity of mercury is lowered by the addition of sodium rather than increased, which would be the case if the metal were in mercury in an ionized state. 3'1th studied the conductivity of very dilute sodium, potassium, and lithium smalgems and found that each exhibited a somewhat different behavior in mercury, but that all decreased the conductivity. Vens’conehh measured the electrical con- ductivity of 20 different sodium amalgams from O to [5 atom per cent mercury and reported that changes in conductivity occur at compositions corresponding to breaks in the thermal diagram for the sodium-mercury system. Vanstoneb'S determined the specific volume of sodimn-mercury -23- H. alleys and reported that mercury contracts on the addition of sodium up to concentration or 118 per cent soditm. Vapor pressure measurements of the alkali nets). uelgsss show that compound formation takes place even in very dilute solutions.“ Thallium and the elements or Groups I. and 11 actually form compounds with mercury, since the melting points of. the malgms are higher than the melting points of either or the cmponents; oldie other metals, except those of group VIII, fem solu- tions or isomorphcus mixtures with mercury.)47 The Mmtic Properties of Amalgam The ionic state of a particular metal in solution with mercury can be predicted from magnetic susceptibility studies which provide a means for detemining the difference in the number of free electrons in the pure metal and in mercury solutions of the metal. If a Group I or Group Ia element goes into solution with mercury as a neutral atom the diamegnetic susceptibility of the solution should be less than that of mercury as a result of the uncompensated spin of the electron of the element; but if the element is present in mercury in the ionic state the diamagnetism should be greater than that of mercury. Compound formation between elements and merCury may be detected by magnetic studies since systems with odd mmbers of electrons should be less diamagnetic than mercury and systems with even numbers of electrons should be more dia- magnetic .h8 The magnetic properties of the 511181ng of gallium, gold, indium, and tin were studied by Davies and Keeping;19 those of zinc, cadmium, -29- his-nth, copper, chromium, manganese, and silver, by Bates and his so. where _h8 .50 51,52 .53 The magnetic properties of the sodiumomercury system «are studied by'rrsnkn and Kata;h who investigated amelgams of compositions between 21 per cent and 95 per cent sodium by weight. Their investigations shoe that sodium is in a state comparable to that in which it exists in comentrtted liquid anaemia solutions, rather than in the form of atoms. They were unable to show definite breaks in the magnetic susceptibility~ composition diagrams at compositions predicted from thermal analysis of the sodium-mercury system. 55 measured the magnetic susceptibility of dilute Aravamuthachari sodium amalgame containing up to 10 atom per cent sodium and found that the diemagnetic susceptibility decreases below the value for mercury slowly at first, then more rapidly, finally leveling off and again increasn ing. He found that as little as 0.02 atom per cent of lithium increased the diamagnetism of mercury but that greater concentrations reduced the diamagnetism to slightly'leee than that of mercury. Mercury became less diamagnetic when very small quantities of potassium or rubidium were dissolved in it, but more diamagnetic, when greater than 0.05 atom per cent was added. Klamm and Banachulzg6 made a thorough investigation of the magnetic susceptibility of the alkali amelgams at compositions between 0 and 100 atom per cent of the alkali metals at 20°C and at 483°C. In most cases the maxima, minima, and direction changes in their compo- sition-susceptibility diagrams correspond to compound formation .30- predicted by tramway-is, although a few points should be further investigated. Dilute solutions or potassium and rubidium in mercury exhibit much greater dimmetiu at 483°C than at 20°C, while the susceptibility of lithium and sodium malgsms were relatively unchanged at the lower temperature. The ngtic ProErties of Mercury Hepatic susceptibility studies for amalgams have led to several detailed investigations of the magnetic properties of mercury. The ex- perimental value reported by Slums7 for the atomic susceptibility of mercury vapor is ~78 x 10'6 which compares well with the theoretical value of «815.6 x 10“ calculated for mercury as a monatomic gas. Liquid mercury is probably polyatomic since the atomic susceptibility at room temperature is -33.8 x 10“. Mercury has a rhombohedral structure in the solid state and a close-packed structure in the liquid state.58 Apparently electrons move much more freely in the solid mercury than in liquid mercury because the electrical resistance of the solid is only one-fourth that of the liquid. Moreover, mercury is less diamagnetic in the solid state than in the liquid. The magnetic susceptibility of solid mercury has been reported at several temperatures. Vogtsg determined the atomic susceptibility parallel and perpendicular to the trigonal axis in single crystals of mercury at liquid nitrogen temperatures and reported an average value for the gran susceptibility of -0.118 x 10-6. Owen60 reported the value -O,15 x 10'° for the gram susceptibility of mercury at ~80°C and Oxleyél reported -o.1ss x 10"3 at 430°C. -31.. Theoretical Discussion conductivity and magnetic susceptibility studies have supplied the lost information about the nature or the metallic solute in various snslgsns and should supply similar information for ammonium amalgam. % The measurement of the conductivity of monim amalgam was contemplated but found infeasible, as a result or the tendency for the malgam to decompose into gaseous materials with the formation of bubbles which wuld increase the electrical resistance and invalidate any conductance data. The Gouy method for determining magnetic susceptibility appeared to be acceptable for studying the properties or the ammonium-mercury system. Bates62 has designed an improved apparatus for measuring magnetic susceptibility in now-homogeneous systems such as amalgams. Actually the Sony method should be suitable for determining whether ammonium anslgan is dianagnetic or paramagnetic and should give some information on the variation of magnetic preperties with composition. In the (Sony method the magnetic susceptibility of a sample is de- termined by weighing the ample in an inhom0geneous magnetic field. The apparatus illustrated in Figure 3 had been constructed for earlier investigations in this laboratory.63 The magnetic field exerts a force along the length of a cylindrical aaaple proportional to the field strength according to the following expression:6h it F ~l/2(k1 - k2) H‘A 2: g Aw, fiThe letter .15 is substituted for the Greek letter kgppa, which by convention represents volume susceptibility. -32- C Figure 3. The Gouy magnetic balance ~33- ” ~ ‘ ‘. «R i gl‘v«‘.. x . .- l ,t - ,1. .. ._ M k; - the volume susceptibility of the snple, k. - the volume susceptibility of air (or medium in which the tube is suspended), E - the magnetic field strength in Oerateds at one end or the smple (naming the other end to be in zero field), A - the cross-oectional area of the sample 1'. e at the position of the septum and was 0.369 cm. for these measurements, g . gravitational acceleration, and A w - the change in weight of the sample produced by weighing in the magnetic field. Rather than determining the field strength at each applied current it is simpler to calibrate the apparatus with a substance of known volume susceptibility and compute the susceptibility in c.g.a. units/gr). directly by the relation «n X1 -: kair — kaaVi fl!- fli [1‘73 where k; and A w; are the volume susceptibility and the corresponding weight change at a given field strength for the calibrant, while /1 and A u; are the density and weight change at the same field strength for the ample, Traces of ferromagnetic impurities in a sample can completely conceal the true magnetic properties. Ferromagnetiam varies with field strength while paramagnetiam and diamegnetism do not vary, so that in *The letter I will be used to designate the Greek letter phi, the usual symbol for gran susceptibility. -314- tb any nestled e11 saples sre weighed at s series of. different field strengths to detect errors prodsoad by iann-ities. The ngnstio Susceptibility Measurements status The magnetic susceptibility of monies: amalgam had to be measured at temperatures at which the smslgsn was stable, so that an apparatus which provided a means for cooling the sample tube was constructed as shown in Figure 1;. The magnetic susceptibility tube 0 was made from 8 III. o.d. Pyrex tubing with e, septum 10 cm. from the reference mark and 3.25 inches from the bottom of the tube. it the tsp of the tube was a I 7/25 Joint. The corresponding male Joint was sealed at the top and contained a loop for connection to a gold chain with which the tube was suspended from the left pen of the balance. The tube was enclosed by the docket A which extended some distance above the Dewar flask to prevent movement or the chain to the sample tube by air currents. The Jacket A was surrounded by refrigerant in a Dewar flask. The Dewar flask was constructed in the glass shop from Pyrex tubing. Prior to silvering, the inner walls of the flask were cleaned with chromic acid solution, rinsed, cleaned with 50 per cent hydrofluoric acid solu- tion, and finally rinsed with distilled water. A reducing solution of dextrose and water was added to alkaline silver nitrate and the mixture was poured between the walls of the flask. The flask was strip-silvered to permit viewing of the interior. After the silvering solution was removed the coated surface was rinsed with distilled water and the flask .35- O SCALE I9 any 2%, 5" §°'°'\ A REFERENCE MARK \ C SEPTUM J/ o_ SCALE V x Figure 1;. Left: Apparatus for low temperature measurement of magnetic susceptibility: A, jacket enclosing sample tube; 8, sidearm for nitrogen inlet; C, magnetic susceptibility tube. Right: Detailed drawing of tube C, ‘1 a’ N I INCHES I um mean-nova: st 200%. no flaskm sealed to "mum and am 11:11. being hosted with a bushy nm at about hoo°c. In order to "love adsorbed gases more completely a charcoal-liquid air trap at reduced pressure III opened to the evacuated flask for about thirty minutes before the flask was sealed off.65 merimental Procedure «- The refrigerant employed for these measurements was boiling Freon-12 which was liquefied as it passed from the cylinder through a copper coil interned in isopmpyl alcohol and Dry Ice. Pressure from the tank forced the liquid through a Teflon tube into the Dover flask. With the Dover flask filled with boiling Freon-12 the temperature at various levels inside jacket A was meesured with a thermocouple and was found to differ with the height of the tube; however, in the vicinity between the pole pieces the temperature became constant after 20 minutes within 0.50 of -29.8°C, the boiling temperature of Freon-12. Before each series of measurements at low temperatures, where condensation of moisture on the sample tube might interfere with the weighinge, the air in Jacket A was displaced by nitrogen dried over Drierite. .51:- was displaced from the Jacket A by passing nitrogen“ into a length of 3 mm. i.d. rubber tubing which entered at the top and extended to the bottom of 13.. After about 20 minutes the tubing was removed from the jacket and connection was made to the nitrogen supply through the side-am B. A slow stream of *Hathieson dichlorodifluoromethane . “Ohio Chemical Company water-pumped nitrogen, dried over Drierite. -37- dry nitrogen was passed into this side-er- end out through the top to prevent Hoist sir tron entering the apparatus while weighings were being node. The field strength of the magnet at currents of O, h, 8, l2, and 16 spores was detersined by calibration with Hohr'e‘ salt at ~30°c and I180 with sir-free conductivity water at room temperature. The gran susceptibility of Hohr's salt is and the gran susceptibility of water is -0.720 x 10-. at 20°C.,614 The Hohr'e salt was freshly ground before it was packed into the tube, since it was observed to become less paramagnetic on standing in air. The data for these calibrations appear in Table I . The Magnetic finceptibility of Mercury at Low Tmrature he a preliminary to making a magnetic study of monium amalgam the magnetic susceptibility of mercury“ was measured at room temperature to compare the gram susceptibility with the values obtained by other in- vestigators. Bates66 found that the gran susceptibility of mercury varied with the purification process and that it decreased slightly upon standing in air. Apparently no particular precautions Vere necessary to purify the mercury for the present investigation since a value of -e -O.166 x 10 was obtained for the gran susceptibility at 25°C as compared i‘Merck Reagent Grade hydrated ferrous amonimn sulfate. “metal Salts Corporation High Purity mercury. -38- with Batss' value of no.168 x 10". Prior to weighing, the mercury was carefully poured into the sample tube which wes then connected to an sspirater to draw off bubbles of entrapped air. The weight of the sample and the mercury nus about 70 grams, shich was large for making neighings on e semi-micro balance. The change in weight upon applies. tien of the field was sufficiently large that weighings were only made to within 0.1 mg. The magnetic susceptibility of mercury has never been determined in a single series of measurements at several low temperatures by the flow method. It was decided to obtain magnetic susceptibility data for mercury at -29.8°c, the temperature of boiling Freon-12; at -7590, a temperature readily obtained with Dry Ice-ieopropyl alcohol; and at 490°C , the boiling temperature of liquid nitrogen. Prior to these measurements the magnetic properties of the susceptibility tube when filled with dry nitrogen and weighed in nitrogen were studied at the temperatures at which mercury was to be investigated, The tube was in- creasingly paramagnetic at low temperatures necessitating an appreciable correction for the change in weight of the tube at each field strength as shown in Table II. The samples of mercury were weighed in a nitrogen atmosphere during measurements at low temperature and in air for measure- ments at room temperature. The data for these measurements are listed in Table III. The temperatures were measured with e copper-constantan thermocouple in conjunction with 3 Leeds and Northrup Electronic Potentiometer. The values at -30°C are not different from those at room temperature by amounts larger than experimental error. The value at -39- TABLE I GALDRATIOH 0? TE FIELD more 0! THE mmrmmm Mo hr ' 3 Salt Field Strength Conductivity Field Strength (-29.6) (Oerateds Wags; (Oereteds 2 A V A v 0 .1131; 3880 .0 .0020 37 80 0.521: 73a) -0 .0077 7&20 0 .866 9500 -0 .0127 9520 1 .097 106 80 -O .015 8 10630 TABLE II MWETIC SUSCEPTIBILITI TUBE CORRECTIONS AT VARIOUS TEMPERATURES Field Strength - A A W (”5-) (Oersteds 25"0 —29.8'C -75"C -19h"C 3830 0.0000 0.0001 0,0002 0.0002 7380 0.0000 0.0002 0.00014 0.0001; 9500 0.0000 0.0002 0,0006 0.0006 10600 0.0000 0.0002 0.0007 0,0007 , 33. o ammo. 0 ammo. 04.4.0 0.5.0 2.00.0 0.00.0.0 0000.0 050.0 00mm 0.3. 0 M08. 0 008. 0 H08. 0 008. 0 002. 240 300.0 300.0 «000.0 28.0 000m now u 03.. u a 0.3.0 008.0 003.0 0000.0 008.0 0000a 09.0 02. 0 a 0. 0 008.0 mane. 0 fine. 0 0000 02.0 00.8.0 $8.0 $8.0 0.2.0.0 003 and. 0 0m8.0 200. 0 G00. 0 $00. 0 0000 00H H mp- .- .0 00H. 0 030. 0 «20. o 030. 0 0000a 0.00. 0 00a. 0 008. 0 00m 0. 0 008. 0 00mm 0.00.0 030.0 080.0 090.0 002. a.” m0H.0 0000.0 0000.0 0000.0 000m 4 000.0 0. 08- . 0 03.0 00.8.0 £000 0000.0 930.0 0200 0000a 03.0 03.0 38.0 008.0 58.0 008.0 2.8.0 0000 m0H.0 50.0.0 0.80.0 0000.0 030.0 0000.0 002. 000.0 0000.0 0000.0 «000.0 0000.0 800. 0 000m 00H H mm n 0 “.00 00 A53 0 m m H $000203 00H x M- 00.0 n N. 0000200 oral q AJEV 3 4 0H0?“ gas w§> a... Museum: 8 NEHmHBn—Masm 3564: a: H MASH ~190°c lo identieel with the ever-go of Vow-59 results .0 483°C Melted tro- eingle crystal studies. However, the only other nee-m- lent reported in the vicinity of 45°C was that of 0x1ey61 who reported e gra- susceptibility or 0.15 x 10" which differs significantly from the value obtained in these experiments. The results of the measurements at room temperature and at the temperature of liquid nitrogen agree well with those of other investigators; therefore, it can be concluded that the values obtained at -30°C and 45°C are also acceptable. The Hmetic Susceptibilitz of Ammonium Amalgam at -3o°c While the mslgm was being prepared the air in jacket A was dis- placed with dry nitrogen and the Dewar flask was filled with Freon-12. The magnetic susceptibility tube was kept stoppered at both ends in the "cold box“. At the completion of electrolysis the tube was carefully filled with purified amalgam, particular care being taken to remove bubbles from the sample. The amalgam was "pushed" into the tube by pressure from a stream of dry nitrogen. when the tube was filled to the mark the top was secured with a ground glass joint and the filled sample tube was placed in a jacket made from 12 mm. o.d. Pyrex tubing. The jacket containing the susceptibility tube was placed in a Dewar flask of. boiling Freon-12 inside the cold box, while the Dewar flask containing I jacket A in a Freon-l2 bath was moved from its position between the pole pieces of the magnet into the cold box, With the Dewar flask containing Jacket A claaped inside the cold box the filled magnetic susceptibility tube was quickly wiped with absorbent tissue and the stopper was removed -ha- 'l from the bottom opening of the tube. The top was removed from jacket A and the magnetic susceptibility tube placed in position with the chain passing up through the Opening in the top. A cork placed in this open- ing along with the chain held the sample tube in place while the apparatus was removed from the cold box to its position between the pole pieces of the magnet. The chain from the sample tube was joined to the balance chain and as soon as possible a stream of nitrogen was passed over the tube. After 20 minutes weighings were made at the various calibrated field strengths. Immediately following a series of weighings the sample was poured out into standard sulfuric acid. After decomposi- tion of the amalgam the excess acid was backrtitrsted with standard base. The gram susceptibilities X, measured at various field strengths, the densities/47, and the compositions of the amalgams are shown in Tables IV and V. The relation between the density of the amalgam and its composition was not known, so that several additional densitybcomposition measurements were made to obtain data for the more dilute and the very concentrated amalgams. The results of this study appear in Table VI. A tube other than the magnetic susceptibility tube was used as a pyonometer in this particular case. Discussion of Results In the investigation of 19 ammonium amalgams, all but two were more diamagnetic than mercury. No obvious relationship exists between the composition and the dismagnetism of the amalgams. When the density is TIBLE IV THE SPECIFIC MAGNETIC SUSCEPTIBILITIES 1ND DENSITIES OF AMMONIUM AMLLGAHS 12 ~30°c L n—L — //9 880 Oerateds (gms./cm.3) A40 —X x To 7380 Oersteds 9500 Oersteds ---———-——-———0 10700 Oersteds m Aw-XxlO Aw-XxlO" 13.8 0.0065 30.167 0.0233 0.105 0.0387 0.165 0.0h97 0.167 12.0 0.0062 0.183 0.0226 0.183 0.0376 0.185 0.0h8h 0.186 11.3 0.0060 0.188 0.0225 0.19h 0.0373 0.198 0.0b78 0.196 10.3 0.0027 0.096 0.0275 0.260 0.082 0.2h3 0.050 0.223 10.1 0.0052 0.18 0.0239 0.231 0.038h 0.228 0.0h99 0.230 9.80 0.0058 0.219 0.0220 0.228 0.0362 0.227 0.0h67 0.231 9.23 0.0057 .0.27 0.0217 0.229 0.0363 0.232 0.0060 0.232 9.16 0.00h7 0.186 0.0213 0.226 0.036h 0.23h 0.0h6h 0.236 9.03 0.0073 0.29 0.0211 0.227 0.0358 0.231 0.0hhh 0.229 8.56 0.0059 0.2bh 0.0211 0.280 0.0350 0.2h1 0.0bh8 0.2h2 8.05 0.0055 0.2h2 0.0199 0.2b1 0.0336 0.2h5 0.0029 0.2h7 7.70 0.0070 0.32 0.0219 0.277 0.0350 0.268 0.0h77 0.270 7,27 0.00n7 0.229 0.0178 0.238 0.0301 0.2hh 0.0801 0.256 7.05 0.00h8 0.2hl 0.0186 0.257 0.0306 0.256 0.039h 0.259 6.51 0.0089 0.267 0.0173 0.259 0.0292 0.261; 0.0373 0.265 5.95 0.0036 0.219 0.01hh 0.235 0.0230 0.232 0.0305 0.239 5,27 0.0027 0.18 0.0101 0.186 0.0170 0.189 0.0217 0.191 1.10 0.0018 0.16 0.0067 0.159 0.0116 0.167 0.01h6 0.165 3.93 0.0018 0.1h 0.005h 0.138 0.0092 0.138 0.0118 0.139 TABLE V CGIPOSHIONS or MOMS Hillimoles Hole Per Cent (elm/a3) -x x 10‘ Holes Hg NH. )1 13.8 0.16? 0.251; 0.000 0.0173 12 .0 0.186 0.221 0.69 0.312 11.3 0.196 0 .208 1.35 0.6119 10 .3 0 .233 0 .190 0 .698 0 .367 10.1 0.230 0.182 0.218 0.120 9.00 0.231 0.17h 9 .23 0.232 0 .170 0 .hTh 0 .279 9 .16 0.236 0.169 0 .h56 0.270 9.03 0.229 0.166 0.6110 0.385 8.56 0.2112 0.158 0.560 0.355 8 .05 0.2117 0.108 0.353 0.239 7 .70 0 .270 0 .1h2 0 .206 0 .1175 7.27 0.255 0.13h l.h3 1.07 7 .05 0.259 0.130 O .66 0.507 6.51 0.265 0.120 1.6h 1.37 5 .95 0.239 0 .110 0 .1431: 0 .395 5.27 0.191 0.0973 1 .85 1 .90 h .10 0 .165 0 .0752 0 .1172 0 .219 3 .93 0 .139 O .0727 l .37- l . 89 TABLE VI THE RELATIONSHIP BETWEEJ DENSITY~COMPOSITION DATA OF WORM [MALONE / (gm/ml.) 10010 Per Cent 0 13.61 0.0 13.61 0.059 13.51 0.001 13.h3 0.002 13.33 0.002 13.03 0.021 10.11 1.h5 9.770 0.172 9.231 0.2110 8.672 0.272 8.201 0.595 5.798 0.122 3.h69 1.10 -35- plotted versus dinagnetian as shown in Figure 5 the points fall on two intersecting curves. the naxilun specific susceptibility .0370 x 10" 0.3.0. nits/al- was observed for a suple with density 7.10 p./n1. The relationship between magnetic susceptibility and density would be are understandable if the density were a function of the composition. the composition-density data suggest that the amalgam contained some gaseous monia and hydrogen produced m the partial decomposition of the malgas under mich circmtances the concentration of anncnium as determined by titration would include a concentration of mania gas and would not represent the exact composition of the amalgam. Other impurities in the analgsn consisted of small quantities of ammonium chloride, water and alcohol all of which should have remained largely at the upper surface of the malgan where the magnetic field was weak and their effect on the magnetic properties of the analgam were small. Following decomposition amelgams contracted so that a volmne of mercury less than sufficient to cover the reference mark remained in the tube, a situation which made weighing of the residue in the magnetic field meaningless. However, the magnetic susceptibility for dilute endgame which did not contract appreciably following decomposition was essentially the ewe as mercury. A similar result was obtained if before weighing enough mercury was added to a decomposed concentrated amalgam to increase the volme to the calibration mark of the tube. Five enslgsns had enmonim concentrations between 0.270 and 0.395 mole per cent and specific magnetic susceptibilities between ~0.229 x 10" .177- o 2 4 6 8 IO I2 l4 /0AMALGAM (GM/CC) Figure 5 Gram susceptibility-density relationship for ammonium amalgam at -30°C -L8— and 4.239 x 10". The specific susceptibility of woman in each of these uni-gens was calculated from the relationship fibre '98 and P33; represent the respective weight fractions of mercury and mains. The data necessary for these calculations and for the calculation of the corresponding molar susceptibilities appear in Table VII. The average value «41100 x 10“ for the molar susceptibility of monium seems impossibly high. This must mean that the Brillcuin zone in mercury is nearly full and that the few electrons supplied by as little as 0.3 mole per cent of ammonium suffice to complete it. The small concentration of ammonium apparently removed the paramagnetism of the metallic electrons in mercury. If this explanation is correct then the specific susceptibility of amonim amalgam represents approxi- mately the specific susceptibility of mercury minus its temperature independent parmagnetism. Under these cirmnnstances the diamagnetic susceptibility of mercury is about «0.23 x 10'"6 per gram and «116 x 10'”6 per mole which is not unreasonable. If the amalgam consists of a mercury solution of a compound such as NH‘ng, which is comparable to certain sodium and potassium compounds with mercury, then the molar susceptio bility of NH4H313 when calculated on the basis of the present measurements would be about ~5000 x 10-e which is an unlikely value for such an entity. Indeed, the fact that armnonium, unlike all the alkali metals except lithium, has no vacant orbitals with which to form inter-metallic ~h9- new V1: ‘ m um suscmmnm or moms n mourns was ~X..1: 10' Hole Per cent «Xx 4,41: 101' (13.3.1. finite/a.) HR. (c.g.e?‘mits/m. ) (o.g.l.un1ts/mole) O .229 0 .385 130 3200 0.232 0.279 260 Moo 0.233 0.367 210 3300 0.236 0.270 290 5200 0.239 0.395 200 3600 Avg. 230 Avg. M00 ~50- Wange-tsthetanionicoe-pousdottbe typem'lg; not exist. Sacha oo-poundlaybe analgeus to t). 'polyadsoic" con- pounds which sodium ferns with lead and tin in liquid monis. The amend '1‘,qu ilperte the properties of an electrolytic conductor rather then of a metallic conductor to its solution in liquid mule; during electrolysis of such solutions sodium ions go to the cathode and Pb," ions go to the anode. t. conductivity study of monixm amalgam simuld are further evidence as to the similarity of its structure with that o! the 'polyanionic" conpounds described by finckeléég however, the gaseous decomposition products of the amalgam make such a study impractical. It may be sewed that the density of an amalgam corresponds approxi- mately to the concentration of ammonium in such a way tht the density is least for the more concentrated amalgams. The relationship between dense ity and specific susceptibility as diagramsd in Figure 5 then might be interpretable. In the system ammonium-mercury two opposing effects appear to be in Operation with regard to the magnetic properties. 0n the one hand an increase in concentration of ammonitm decreases the density and reduces the paramagnetism of mercury as described previously, while on the other hand the decrease in density alone tends to increase the paramagnetic susceptibility component of the free electrons as shown by 81.009155 and verified by Bates and Baker67 for mercury, When the increase in paramagnetism produced by the decrease in density overcomes the effect of additional amonium on the temperature independent paramagnetism a slope change appears in the plot of density versus susceptibility. -51- n. more new II THE smut MW Theoretical Introduction A useful :0th for establishing the relationship between two sub- stances in solution consists of determining the freezing points of different solutions of the two components. The two substances tom s true solution in which there is no interaction between the components if the frosting point of the solvent is decreased by the mount predicted from Rsonlt's law and the Clausius-Clopeyron equation, A 'r - 23%03111 Na, in which xi T is the freezing point lowering, To is the freezing point of the pure solvent, A H is the molar heat of fusion of the solvent, and N8 is the mole fraction of the solute. The freezing point depression of the solvent will be less than that predicted by Rsoult's law if the solute forms polymers or if the solute and solvent form compounds; it will be greater than predicted if the solute dissociates to form additional species,68 and it may be greater, or less, if the components fern solid solutions.69 Different solutions of two substances frequently exhibit a different behavior; for example, the components may form an ideal solu- tion at one concentration of the solute, and a compound at some other concentration. Generally when two substances form a compound, and no solid solutions form, a eutectic composition exists at which one pure -52- cusps-sat and the compound fresco out of solution simultaneously. For a tie component system the freosing temperatures at various concentrations new be plotted to form a phase diagram from which the composition of compounds and eutectica is established as shown in Figure 6. The method of thermal analysis, in which one plots time-temperature curves during the cooling of a particular solution, provides a useful means for obtain- ing data for making a phase diagram. Whenever a phase change or transi- tion in structure takes place during the cooling process, the rate at which heat is evolved from the system changes, and thus the slope of the cooling curve is altered. In Figure 6, curve I represents the time-temperature plot as a.pure substance is cooled below its freezing temperature. The temperature remains constant at the freezing point until all the liquid has solidified and than the temperature falls uniformly again. Curve II is a typical cooling curve for a two component system which shows only a simple eutectic point. The first break appears in the curve when solid begins separating out with evolution of heat and a corresponding change in the cooling rate. As the solid phase forms the composition of the solution varies continuously so that at no time does the temperature remain con- stant until the eutectic composition is attained. The length of time during which the temperature remains constant at the eutectic point varies with the original composition of the solution and is a maximum for the pure eutectic solution. -53.. If. if! {153th TEMPERATURE TEMPERATURE 'I II COMPOSITION COMPOSITION Cooling curve for a pure Cooling curve with eutectic substance. halt in a two-component system. . B A TEMPERATURE E. x 52 COMPOSITION Figure 6. Phase diagram for a two-component system with a compound of composition x, and eutectics with compositions E1 and 3;. -5h— Historical Summary Amalgams are two component systems for which rather complete phase diagrams are available. In the phase diagrams for lithium, sodium, and potassium amalgams several maxilla appear as a result of compound forma- tion with mercury .70 A {reeling point—composition study of ammonium wedges: should provide information concerning the nature of the substance, and particularly as to whether compounds fem between ammoniu- and mercury. Rich and TrmerslS reported in 1906 the freezing points of eeverel amoniun amalgam prepared from sodiun amalgam and amonium iodide in liquid ammonia. In Table VIII appear the results of their investi— gation which are not entirely consistent, but do suggest that the freez- ing point lowering constant of mercury decreases as the concentration of 7 monimn increases. Bent 1 calculated the freezing point lowering of mercury to be 1.900 per atom percent of solute for dilute solutions obeying Raoult's law. Using Vanstone 'shS phase diagrams of sodium amal— game , Bent Verified the calculated value. For the more dilute amalgams in Rich and Travers' investigation, the freezing point lowering evaluated with Bent's value agrees favorably with the experimental results, but for the concentrated amalgam the behavior is non-ideal. ‘ Introduction to Emerimental Procedure A phase diagram obtained by determining the freezing points of monium amalgam of various compositions should show whether compounds of the type NH‘ng do, or do not, exist. However, certain observations during this present investigation suggest that the freezing process in ammonium amalgam is not a simple one. Ammonium malgams appear not to -55- _ TJBLE VIII DEPRESSION OF THE FREEZING POINT OF MERCURY BY AMMONIUM (Freezing point of mercury a —39,hO°C) (he. Nil." Hole Freezing“ Prefiizted ’ ‘ 100 HEms. Pegfiient Pzgg; (A63) bygéuiory for Mercury ’ 0.0092; 0.101; ~39.62 0.22 0.20 [no 0.0117 0.13 -39.67 0.27 0.25 hzo L 0.027 0.30 410.01 0.61 0.57 1:10 0.079 0.88 440.81 1.19 1.7 320 0.081: _ 0.93 4.1.605 1.99 1.8 mo odds h.7 -hh.82 5.20 8.9 230 0.507 S .6 ~16 .61 5.99 10 220 *From observations by Rich and Trevor-.15 - JIL! Ifl fit the one consistency after fussing and halting as they were before Ms. M a tube of seals-I prepared by electrolysis is immersed in s Dem flask cont-fining liquid nitrogen, gas is rapidly evolved and the odor of flesh is very apparent. The upper surface of the uslgsn attains a sponge—libs appearance with large bubbles being interspersed 1n the serum-y. Upon warming a frozen amalgam additional mania appears to be evolved, but a second freezing is usually not acoompsnied by so vigorous a release of gaseous material as a first freezing. A qualitative measurement of the volume of gas released by an analg- dnring freezing was made . Inside the cold box the magnetic susceptibil- ity tube was filled with amalgam and immersed in a bath of boiling Freon-12. The tube was attached to the gas burette previously used in the analysis of some amalgam. With the malgm at the temperature of boiling Freon a slight increase of about 0.2 ml. in volume was noted after five minutes. when a liquid nitrogen bath was substituted for the Freon bath bubbles were evolved from the amalgam but the gas burette showed a decrease in volmne due to the contraction of the amalgam and gas at the liquid nitrogen temperature. Upon warming the frozen amalgam: in Freon-12 the volume of gas in the system had increased to about two milliliters. An additional freezing and melting produced no observable volume change. Apparatus for Recording Cooling and Warming Curves The freezing process of monimn amalgam was investigated by obtain- in; a series or cooling curves for several analgsms in threetypes of .57- -:———_ Wt. In each use the apparatus canister! of a fussing hubs M the .algu, an air jacket to keep the cooling rate unifon, and I Dower flask for innersing the ample tube and Jacket in a suitable refrigerant. The telpsrature in each of the three different experiments was seamed with ocpper-constantan thermocouples oomeotod to a Leeds and lorthrup Type [-2 Potentionotor. In addition, complete cooling and lasting curves were produced on a Brom-Ebneywell Electronic Recorder operated in conjunction with a Leeds and Horthrup 13,0. Indicating Auplifier md a bucking voltage produced by three 1.5 volt dry cells and regulated with the slide wire of a Leeds and Northrup Student Potentiometer. The circuit diagram appears in Figure 7, Without addi- tional modification a.maximum potential of 2.b millivolts could be measured with the amplifier and recorder with a sensitivity of only 0.2 millivolts (about six degrees) per inch of recorder tape. for the proposed study of the freezing process in ammonium amalgam both the range and the sensitivity of the recording potentiometer were increased through use of the bucking voltage which, as seen from Figure 7, was a variable e.n.f. opposed to the e.m.f. produced by the thermocouple junctions. By opposing the potential difference between the thermo— couples vith a sufficiently large lmom voltage the total potential difference was reduced to any suitable small value which could be unpli- tied to satisfy the requirements of the experiment. At any time the e.m.f. which represented the difference in temperature between the two junctions was the sum of the absolute value of the bucking voltage and ~58- TYPE K-2 POTENTIOMETER + _ L THERMOCOUPLES r 1,, d BUCKING VOLTAGE ___._._._ _ . l— , 7 . | i 8‘? <; . <> . l = :>" :r B <: l <> - <> {t :> , ,, 3 I A <: ‘ w P L:-‘ ‘- ‘ l :i e; -_ , b j . _ l___ _ _ J ;. m T 5-: '5‘ \ fl ; , a; . x '- 1» J; ‘ \ AMPLIFIER fl ) ) ELECTRONIC RECORDER :- $ _ 1‘ NA _~ \_~.e‘ «T If ee- - Figure 7. Schematic diagram for recording cooling ~ - , curves: A, Heathkit Resistance Decade for coarse adjustment of bucking voltage; B, slidewire of L. a )1. student potentiometer for fine adjustment. QM voltage read from the recording potentiometer. A scale unfit-ire .w to allow detection of null arrests in the cooling curves was sanitary, to that sufficiently large bucking voltagel were introduced to take the scale factor either 0.02 or 0.65 nillivolte per inch in all the recorded cooling curves. A maximum smut. of 1.6 volts could be matured in thin way without the introduction of a voltage multiplying device on the potentiometer. The exact o.m.f. produced by the thermo- couple at any time we read from the Type X-2 potentiometer and simul- taneously marked on the recorder tape. From the Type K-2 potentiometer reading and the scale sensitivity of the recorder, the voltages could be accurately calculated for each setting of the bucking voltage without actually knowing the bucking voltage. Cooling and Warming Curves for Each of the Two Phases of an malgem Eagerimental Procedure The first type of experiment performed in the investigation of the freezing process of ammonium amalgam was the oinmltaneoue procurement of cooling curves for each of the two phases of an malgam in on attempt to distinguish differences between the phases. If the upper phase con- tains a higher concentration of ammonium, combined in some way with mercury, than the lower phase contains, then the cooling curves of the two phases should be dissimilar. The effect on the freezing point of successively freezing and melting the same unalgom was also investigated. the Ming temperature or an malgam should differ:- atter freezing and letting it the composition changes during freezing. ‘l‘u thermocouples were used for measuring the temperature of each 0! the two phones independently. To keep the phases separate stirring was eliminated in this particular experiment. In most freezing point determinations stirring is necessary to keep the temperature of the ample uniform throughout, but stirring is not so essential when a good thermal conductor-och as mercury is a large constituent of the material under observation. At the some time the good conducting properties of mercury may have been a hindrance in this study because the two phases of the analgama were in no way insulated from one another, so that some of the heat produced by changes in one phase was probably transferred to the other and may have altered the appearance or the cooling curve for the second phase. For accurate comparison of the temperature in two phases with two different thermocouples the thermocouples had to be well matched. A longer cogent of the thermocouple used in studying the lower phase must necessarily be immersed in the sample than of the thermocouple used in the upper phase. Such difference in immersion depths could introduce a slight temperature deviation between the two thermocouples as a result of variations in the amounts of heat conducted down the wires from the different surroundings of the two thermocouples. To minimize the effect of heat conductance the smallest diameter thermocouple wires available were used, namely, number 140 copper wire and number 30 constantan wire. . m, ‘ 9;: V J \ . (v ,- f' mm was constructed with tea silver-soldered junction, use W for on in ms at 0% and the other Justice m- the 3 sample. ‘20 further lessen the dittmnoes in heat conducted don the if Weuple mm the length of the wire actually exposed to the cold ms was made larger by coiling the wires. A six inch piece of 3 m. toilets tubing was sealed at one and by naming in a smell flue. About rifts” inches of insulation were removed from each wire Just shove one Junction and the wires then coiled around the Teflon tubing with the junction at the sealed end. Along three inches of the Teflon the wires were coiled as tightly and as closely as possible without shorting. The tube was earned very gently to embed the wires partially in the Teflon, after which the tube and wires were covered with a thin cost of polystyrene to protect the thermocouple wires from reaction with mercury in the endgame. In the suns manner one Junction of the other thermo- couple was mounted on the outside of a four inch piece of 7 m. Teflon tubing which had not been sealed at one and. After the coating had hardened on each thermocouple the larger diameter Teflon tube was slipped over the malls:- dismeter tube in a sleeve~like arrangement which permitted adjustment of the relative positions of the two Junctions. The sanple tube was made from 25 m. i.d. Pyrex tubing and was supported flth a rubber stepper inside a jacket made from h; m. i.d. Pyrex tubing. The thermocouples were centered in the sample tube by a one-hole rubber stopper as shown in Figure 8. The two thermocouples were checked against one ‘ acnother by measuring their respective temperatures when both Junctions of each were immersed in an iceowater bath at 0°C, and when one Junction -62 .- 4.. ”v“. _. .._,,.Au.__'_, T0 POTENTIOMETER TO COLD JUNCTIONS -‘ [I'll] Figure 8. Pyrex freezing tube and jacket for studying the freezing process in a two-phase system. The thermocouples are mounted on concentric fluorethene tubes. % “on: n- W My 3:» and u. ethr Junction a. at e' , ‘ ' mm .1 wasted thonooouplu «re m before a sufficiently all m m ns‘ mm. the difficulty in matching m largely it‘ll“: 08 differences in the mount of heat conducted ”on the sur- W eon through the um booms of the difference in level or flu two thsmeouple Junctions in tin ample. The problem was owl-cone by coiling the upper thermocouple up and don the Teflon tube several files end by using e thinner coat of polystyrene on the too them- couples. The tee thermocouples were calibrated, and simultanemnly the purity of the mercury used for preparing the endgame established, by comparing the freezing point of mercury measured by the matched thermo- couples with the freezing point measured by a calibrated themoeouple. the calibrated thermocouple node from oopper-oonttantan was checked at several temperatures with a platimm resistance thermometer and found to compare well with the values listed in tables. The freezing point of mercury was determined from the cooling curve obtained using tin cali- brated thermocouple and the electronic recorder, and was found to be 43.870, or -1.h23 nillivolta, which egress exactly with the best reported freezing point of mercury.” The freezing point of mercury determined from the matched thermocouples was 4.1409 millivolts. A suit- able correction was made for all measurements with these thermconples. Amonim amalgam was prepared by electrolysis, washed in alcohol and water, and dried as well as possible with absorbent tissue. Inside the cold box the freezing tube and Jacket, which had been kept in the cold during the electrolysis, were placed inside a Dewar flask containing -6h. hath. Mflfl.o£fihusl§ummrsdinto firemen-,muammmhamnmuupmuthm Mamie anti/2 inchfmthebetten of the tube sndtheupper couple, centered in the less dense phase. the Dewar flask containing the ample use left inside the cold box during cooling. During coming the mm and tube were removed from the Dewar flask, but kept inside the cold box. The cooling curve produced by either phase a: the assign was plotted by switching the proper thermocouple into the circuit of the recorder. As the temperature decreased the indicator would more to the far end of the recorder scale, but upon introduction of the preper bucking voltage the indicator returned to the zero point and was per- nitted to scan the width of. the scale once again. For each adjustment of the bucking voltage a. Type K Potentiometer reading was made and marked on the recorder chart. Results and Discussion Cooling curves extending down to *7h°C for two malgams were obtained by means of the described procedure. Warming curves were likewise plotted. For two unalgams the successive cooling and warming curves appear in Figures 9, 10, 11, and 12, which were plotted from the data on the recorder chart. During freezing gas bubbles were evolved from the surface of: the amalg-s and the volume of the samples was observed to decrease after the first freezing and melting. The amalgans were not analysed for monim content as it was felt that appreciable decomposi- tion took place during the freezing process and that an analysis after freezing would be of little significance. -65- m o < a: £2 *- z u.) o a) m m o: o u: o | | I I I I 5 MINUTES / DIVISION Figure 9. Cooling curves procured simultaneously for two phases of amalgam 1: extension shows solid state transitiOn; —-— cooling curve for lower phase; _____. cooling curve for upper phase; f,p, of Hg is -38.9°C, ~66— DEGREES CENTIGRADE 8» m l 4:. O I if —42 I I I l I I 5 MINUTES / DIVISION I I J Figure 10. Warming curves procured simultaneously for two phases of analgam I: -—- warming curve for lower phase; ._ warming curve for upper phase; 1‘, p, of Hg is -38.9°C. w. 4 w. s. .3 NH”. m ghlmM‘MWh‘Ew) I, _ .oom.mm- a“ mm no .s .m manage Rona: I 33:9 .833 II "HH =53”me mo $923 25 one how merge mnwehm: pom mnwflooo opfimmwoosm pmafim .HH mhsmfih ZO_m_>_o \ mwFDZE’. m me- «e. G _e-m w... _ 8 oe-@ % O 3 m-m m. w mm-0 3 mm. mm- .oomdmn 3 mm no .m .m “393 yoga.» ll. «3an .833” In «HH Emmdwem Ho 3923 95 93 how mobhpo weighs: 98 33000 gammmoodm 2308 .NH 95%.; 205.20 \ mmhbzzz m _ _ _ _ _ _ _ _ me- me- O 3 :1 w 3 3 3.3 0 m .mm- H w mm- v 0 3 pm. I on! fl- main; point observed from cooling curves with the upper and 1am tbmles in pure mercury are essentially the some. i'hs llasth of the break at the freezing point depends on the quantity of material in the region of the thermocouple and for this reason is shorter for the upper thermocouple, which occupied s more shallow position in the mercury, than for the loser thermocouple. The effect of the amalgam on the freezing point of mercury is not entirely clear. In the series of cooling curves for amalgam I the freezing point at the lower thermo» couple is essentially that of pure mercury. The break produced by the upper thermocouple is not completely linear, but in some cases crosses the freesing point break of the lover couple. During warming the temperature tends to rise near the completion of the break of the upper phase, and during cooling, at the initiation of the break. A slight change of slope appeared during the first cooling of amalgam I in the vicinity of -69°C to -70°C and was not present in the successive warming and cooling curves. During the first cooling of amalgam II the freezing point in the vicinity of both thermocouples was essentially the same as the freezing point of mercury, although a.second break appeared at -h0°C in the cool- ing curve of the upper phase. The second break approximates that of a eutectic break, but does not appear in any of the other cooling curves from this experiment and cannot be regarded as particularly significant. 0n the same cooling curve a third small break occurred at :61°C. The running curves produced by the lower thermocouple in amalgam II are com- parable to that of mercury, although the freezing temperature during the -70- M (reeling end self-in; is lower than tint or nercury. Both inning serves shes thst the temperature or the material near the upper thermo- couple rises st the beginning or nelting, falls for a tile, and then does spin st the completion of melting. Cooling and Homing Curves Obtained During igitation of magma Egerinentel Procedure «I second type of experiment for investigating the freezing process in menial amalgam consisted of freezing an amalgam in s fluorethene tube sttached to the shaft of a reciprocating stirrer].3 The shaking notion of the stirrer provided a means for making the amalgam sample relatively halogensous with respect to composition and temperature. In the appsrems for this experiment a single capper-constantan thermocouple was coiled around s. fluorethene rod attached to the top of the tube as shown in Figure 13. To decrease the rate of cooling the freezing tube was enclosed in a jacket made from sheets of fluorcthene and sealed together with floor-ethane wax. Inside the cold box the sample tube with the Jacket attached was filled with about 30 m1. of amalgm, quickly placed outside the cold box in a Dewar flask filled with Dry Ice-acetone, and connected to the stirrer by fitting the tube over the machined fluorethene top. The reciprocating stirrer was turned on and the amalgam sample moved up and down through the cooling bath as the time-temperature curve was plotted on the electronic recorder in the same manner as in the previous experi- ment. During warming the Dry Ice-acetone bath was removed and the tube shaken in air. Three successive cooling and naming curves obtained by this method for one amalgam sample appear in Figures 111 and 15. -71- the shaft was attached eating stirrer. fl ’4’ 7 .“\\\‘ \\\\ ‘-\\\\\\\\i\\\ I (T Figure 13. Fluorethene freezing tube and jacket: to the chuck of a recipro— .8de we we no d .e Mmqoefincfie 33m Sudan oaflmmom 30;» 983588 "$3.2m 93 3.323 333 umgwdppo HHH EoMHanm no.“ emerge menace mpfimmmoofim .1: mafia 20_m_>_o \ mm._.32:>_ m _ _ _ (D (.0 I 30V89|1N30 8338930 0 q- .OOQ.QMI Mun mm Ho .9 .H m gown—bog. #33233 when HHH Emmdmca mo meager v.55» was cocoon on» no.“ make". 93. .EwMHmE 23. maiden odd? conflcpno HHH sumfimsm you mgneo mnwshms .mH 95mg zo_m_>_o \ mph-42:2 m _ _ A _ _ _ mam l l I " Cd K) 3’ T T l O T sovaelmao 9333930 ll '05 “R l 00 '9 p. '1’ on- -7b- ." 5'5‘ hesults and Discussion Max the first staging the initial break in the cooling curve I i I ,9}??- L W below the freesing point of pure mercury but the temperature [ 15..., use fists the freesing point of mercury before the amalgam solidified. ; it- the iirst warning curve, although slightly erratic above the freezing - g point of moury, contained a definite break at the freezing point of mercury, while in the last two cooling and warming curves the freezing temperature of the amalgam was slightly above that of mercury. Between ‘:"- -56°C and «69°C the slope of each of the cooling curves changed. The f break occurred at a higher temperature and became less pronounced after ‘ each consecutive freezing. The time-temperature curves produced in this experiment suggest i that some decomposition of the amalgam takes place either during freez- ing or as a result of the agitation of the stirrer. A transition in the solid phase which occurs at different tempera- tures depending on the original composition of the amalgam would explain the breaks in the cooling curves at low temperatures. However, since no relationship can be established between the temperatures at which the '1 slope changes occurred and the compositions of the analgsms, "it seems I possible that the break! resulted from failure to attain thermal equilibrium during the cooling process. Gosling ad Waning Curves Obtained While All-onion Assign Wee Decomposing in a Closed System Earhartel Procedure to investigate further the nature of maniacs nelgce a system was devised in much an nelson could be frozen and the volume of hydrogen end manic released during the freesing could be measured. If monim amalgam contains gaseous material onlyloosely combined with mercury some separation of gas from the mercury could be expected when an melgan was placed in an evacuated vessel. Measurements of the volume of hydrogen, which diffuses readily, are better made under reduced pressure than under positive pressure in a gas burotte. The apparatus, as illustrated in Figure 16, consisted of a pump for evacuating the system, a nanometer for measuring pressures between 0.1 cm. and 76 cm., a freezing tube for the amalgam samples, a trap for complete removal of water and alcohol from the amelgsms, and a flask of known I volume for calibration purposes. The freezing tube shown in Figure 17 was made from 114 mm. o.d. Pyrex tubing attached to s 3 19/38 ground joint and the Jacket surrounding the tube was made from 25 mm. 0.6.. Pyrex tubing. The trap D in Figure 16 was used for condensing alcohol or water vapor which remained in the sampleuunder the assumption that most of the alcohol and water would vaporize as soon as the amalgam was under reduced pressure and that the vapors would condense rapidly in the trap surrounded by liquid air. The apparatus would have been improved if a means for stirring the amalgam had been provided, but no space was mmkmEOZ<$ meP OZNwmmu woado OOMJQE .mnfiuoosu weapon somaosm so an uo>Ho>o new mo osuao> one mswaomeos you Eopmzm Ebsoo> .oH ohsmwm QEDQ 2330<> -77- QZDQ ZQmDmEO >m30mw2 NWWHV xmdqm ZOCfimquo we Figure 17. Pyrex freezing tube and jacket for studying the rate of decomposition of an amalgam during freezing: a 10/30 standard taper joint connects to vacuum line. -7 8- sveilahleterputtisgestimrthreughtbtepet thetube endthe Mm of surrounding the seaple with e cooling bath prevented the use of s logistic stirrer. Liquid nitrogen was used as s retrigerent to provide rapid cooling of the useless to a temperature below that attainable with a Dry Ioeoecetone bath. Liquid nitrogen provided too rapid cooling in the previous experiments. Before flask A was sealed to the manifold the volume was calculated from the night and density of the distilled, sir-free water which just filled the flask to the stopcock. The volume of flask A was found to be 51M: m1. With the flask attached to the manifold the volume v o: the vacuum system was determined through the use of the perfect gas relation, P? - P'V'. A volume or V m1. of helium was introduced into the system at P on. pressure and the flask A or volume ‘7' ml. was closed to the manifold. The remainder of the system was evacuated and the helium from flask A was released into the system at pressure P'. The pressures P and P' were measured by observing the level of the mercury in each arm of the manometer with a cathetometer; the when ‘7' of the flask had'previously been determined, so that only V was unknown and was computed from the above equation. “Riv-the measurement of pressure with a mercurycd'illed manometer convention reQuires that the height of the mercury column at the tempera- ture of measurement be corrected to the height at 0°C. Mercury expands -79. on heating; therefore, the height of the column is greater at room temperature than at 0°C and a correction is subtracted according to the equation ho . ht(l-<9.t) where ho and h” are respectively the height of mercury at 0°C and at 15°C. The coefficient of expansion of mercury is represented by (t and has the value 182 x 10‘. nl./nl.°C. The stainless steel scale of the osthetometer amends as the temperature increases, which makes the measured height of A the mercury calm less than the true value and necessitates the addition or a correction to the height of the column at 0°C: no - 11.11 - dt)(1 - Yt) where Y is the coefficient of expansion or No. 18-8 stainless steel and has the value 10 x 10*“ m1./m1.°c. The term which contains the product of. d; by \’ was negligible, so that the corrected value for the pressure readings in this investigation was no - ht(l ~<£t . Yt) - ht(l .- .000172t). The data for the calibration of the volume of the closed system appear in Table III. The volume V measured in the calibration with helium is represented by the expression V - V' + volume of amalgam + volume of mercury displaced in left arm of the manometer 4- volume of flask A, —80- _ TI‘BLbL IX CALIBRATION OF THE VOLUME 0? TH; CLOSED SYSTEM Pressure Volume AWL Volume Velma of. Volume of Helium V' ~- of Fleck Freezing of Ii‘ube System (031.) m1.) (m1.) (m1) (m1.) (m1.) Including 28.56 1302 10.2 51h.2 27.13 750 trap Including 27 .33 1303 9.8 5114.2 271:3 752 ‘ trap Without 31.08 1201; 11.1 51h.2 27 .8 650 \ trap 1 Without 29 .81 1202 10 .6 51h ,2 27 ,8 529 trap -81- where V' is the actual volume occupied by the gas evolved from an amalgam. The volume of mercury (in ml.) displaced in the left arm of the manometer where r was the radius of the nanometer tubing in centimeters and A hL ‘UII the difference in the levels of the mercury at zero pressure and at the measured pressure in centimeters. Before a sample or the amalgam was placed on the line the system was pumped out and then closed to the pumps. A Dewar flask of liquid nitrogen was placed around the trap D and all stopcock: were closed except the one to the left arm of the manometer. Inside the cold box the freezing tube was filled with amalgam, particular care being taken to remove the alcohol and water from the surface of the smalgm. The freezing tube and jacket were assembled as illustrated in Figure 17 and immediately put into place as shown in Figure 16. An unsilvered Dewar flask with liquid nitrogen was placed around the Jacket and the thermocouple wires were connected to the potentiometer. Stepcocks b, c, and d to the liquid nitrogen trap were opened for two or three minutes and then the trap was closed while stepcock e was opened. Under decreased pressure gas was vigorously released from the amalgam. The pressure in the system in» creased rapidly soon after the amalgam was placed on the system and during the initial stages of freezing. Whenever possible several cooling and warming curves were plotted on the electronic recorder for a given amalgam ample. The pressure in the closed system was recorded at the minimnn and maximum temperatures. During warming, the Dewar flask con- taining liquid nitrogen was replaced by a Dewar flask containing iso- propyl alcohol at room teuperature. At the completion of a series of measurements the amalgam was warmed to room temperature while it de- composed slowly on the vacuum line. On several occasions after the amalgam had remained at room temperature for a time the residue was frozen and the pressure at the low temperature recorded. In each case the pressure and volume of the enclosed gas decreased noticeably probably as a result of contraction of mercury in the sample tube and of gas in the vicinity of the cold area. In addition small quantities of alcohol and water vapors which had not been removed earlier may have condensed. That the pressure change after cooling a decomposed sample was not on- reasonably large suggests that most of the alcohol and water impurities had been removed. Droplets of liquid always were present in trap D after a series of measurements. After four to eight hours the decomposed amalgam was removed from the apparatus and the mercury was dried and weighed . Results and Discussion The observations made on five amalgam appear in Tables X and XI and Figures 18 through 21. A sample of pure mercury was also frozen on the vacmm line and a cooling curve plotted down to about 415000 to show that none of the breaks in the curves were produced from solid state transitions in pure mercury. The pressure remained constant while -33- MEASUREMENT OF THzJ DECOMPOSITION OF IMAIEAMS DURING FLUSZING 2ND MELTING T; BLE X Pressure of A h.L A VL Total Volume NH and 52 N33 and Hg ems. (cme.) (ml,) S.T.P, Anal an IV Volume of gas in Erap - 6.5 m1. t - 26° At -7h 5.32 2.70 1.9 119.9 At -3 6.39 3.26 2.3 58.6 At room temp. 10.55 5.32 3.8 92.7 (after 7 hrs.) Anal an V 0 Volume of gas 11 trap - 8.6 m1. 1'. - 29 M. 460° * . 2.73 2.0 65.9 After malting 6.79 3.143 2.5 63.7 At .100 6.72 3.16 2.5 63.2 After melting 8.11 h.12 2.9 7h.2 At -7h° 8.06 1:11 2.9 73.8 After melting 8. h.h5 3.2 78.6 At 460° 8.21; h.20 3.0 75.3 After melting 8.60 h.ho 3.1 78.2 Final 114.23 7.23 5.0 123.7 (after 1; hrs.) Anal an VI Volume of gas in trap a h,8 ml. 1'. . 26° At P1600 * 3.99 2.00 1.11 37.6 After melting 11.11 2.06 1.5 33.5 At - 397,4 1.88 lab 35. After melting 3.80 1.91 1.1: 35.9 At .160" 3.39 1.72 1.2 32.6 After melting 3.10. 1.73 1.2 32 .7 At -160° 3022 1'62 1.1 3101 After melting 3.31 1.67 1.2 31.9 At room temp. 7.33 3.67 2.6 611.? (after n 1/2 hours) After freaqing residue 6 78 3.112 2 h (D 1 *Between ~35°C and 440%. Continued next. page TABLE I ~ Continued Pressure of A hL AVL Total Volume NH and H3 NH3 and H2‘ fans.) (cm3.) (ml.) sm. final yam VII Volume or gen inTJrap‘T—a .2 t - 32° At. -160° 0.98 o.h9 0.35 9.00 Melting) Freezin ) No data Melting? At ~160° * 1.01 0.52 0.37 9.214 After meltin b.68 2.ho 1.70 38.8 (1 hr. later After freezing 14.32 2.18 1.55 35 .9 (1 hr. later) Final 6.10 3 .10 2 .20 50 ,2 Anal am VIII Volume of gen in trap - 3.3 m1. t - 30° At 460° h.ho 2.20 1.6 ho.8 After melting 3.93 1.96 1.h 37.0 Freezing Melting ) No data At -160° h.5? 2.30 1.6 142.1 Final 5.78 2.90 2.1 52.1 After freezing 5.71 2.86 2.0 51.2 residue (460°) *Between -35°C and «440°C. ~85- m. 2. and. o «mas. o 0560. o om. m 0. MN E”. H 0. 4mm HHH> Q3 0 mode 380.0 880.0 fifl 9mm and a. EN H: «w flaw Sad «38.0 380.0 HJH 0. mm Hm; dam H> 04m 43. o 830. 0 $80. 0 h. oa m. E E. H 0. new > 98 and 2.80.0 .3806 m. i m. S 8. H N. 8m pH [Idflulmolnl a5» 3. page 5538 an :5 9 Eu 9:56 83 names“ 5 in :30: 3393 33:5 05%» mm «0 mm tau; «:6 .3.— ofio .5 30: 3.3 can 3?: £93m 3&3 coda no 53 Ewefi Eh .6 mag “5585—4 .5 nounnmogu 2H ago may HH an. 7““ ‘\ , V _ .; .n'.» _‘ {255‘} “I; '. 7‘9.“ :; i. . " ' v -8..." . l l l I 5 MINUTES /D|V|SION Figure 18, First successive cooling and warming curves for amalgam V obtained with the freezing tune joined to an evacuated apparatus; 1’. p. of Hg is ~38.9 C. ‘ .03.st m.“ mm Ho .m .M «mopanmmga copwsogm me op 85% 23 9:3er 2: fie; 333% > gene .8.“ mghg 3.3000 "3.38 use 6.35» aEouem .ma 93mg ZO_m_>_D \ mugbzg m _ _ _ _ _ _ _ _ _ _ BOVBSILNBO $338930 ~88— .oom.wmu ma wm mo .9.“ $3939? nopmsomg cm 0» meadow 00.3 ecrsemgu one 5.? Umqampno b Emmdwsm no.“ agape wficfiws ”$.38 gum John... .9803 .oN madman zo_m_>_o \ mm.52:2 m _ _ _ _ _ _ lo¢l Fm: an BOVHSILNBO $338930 DEGREES GENTIGRA DE -70.... -73.. I I I I 3 MINUTES / DIVISION Figure 21. Cooling and warming curve for amalgam VIII obtained with the freezing tube attached to an evacuated apparatus; 1‘. p. of Hg is -38.9°C. ‘b [up]; was cooled at! mod on the venues line and no changes in slope m amount in the tine-temperature plots. the ”lune of gas present in the system at any tine under stud-rd conditions was represented by the equation v ”tau/w - (volume or system)(2?3°C)P'/760m.1". A small correction was added for the value of mercury displaced in the m of the nanometer by the gas in the system AVL . "IT—ra AhL. :I': The initial pressure was measured after the liquid nitrogen trap had been opened to the system. For this reason the pressure as first measured was the pressure of a volume which included the volume of the trap. The volzme of the gas in the trap at standard conditions was also computed with the above equation and that volume was added to each of the volumes measured after the trap was closed, In Table X the volume of mania and derogen which was released from the analgams up to the time at which the second freezing was begun is listed in the second line of the data for each amalgam in column 5. The per cent of decomposition during the initial exposure to reduced pressure and during the first freezing was calculated, but there is no obvious correlation between this decomposition and the original density or composition of the amalgam. Perhaps the amount of loosely held gas which is present in an anslgam depends on the past history of the sample. The accuracy with which the temperature of the amalgam and the pressure in the closed system could be measured doubtlessly surpass the fundamental errors in the procedure. The temperature of the ammonia and hydrogen in the vicinity of the freezing tube was probably lower than room temperature and the measured volume of the gases accordingly less than if the system were entirely at the temperature of the room. The :.. . means for trapping out alcohol and water may not have been entirely H I effective although the largest decrease in volume observed on cooling a decomposed smalgm to .160°c was about three milliliters as is shown in the data for amalgam VII. tltmugh about 0.5 ml. of this change can be attributed to the contraction of mercury the decrease is appreciable, but should have been much larger if vapors of impurities were present before cooling the tube with liquid nitrogen, .A correction was made for volume of mania and hydrogen which remained in trap D , but the possi-- bility exists that this correction may have been too small because more mania and hydrogen may have been entrapped at the low temperature than 'jinunrla.s_m_i if the trap were at room temperature where its volume was calibrated. Since some of these errors would have opposite effects on the measurements the maximum inaccuracy of the volumes should not be more than about five per cent. The results from this series of observations on freezing amalgems 3 in a closed system indicate that in certain cases ammonia and hydrogen are so loosely held in the amalgan that reduced pressure and freezing remove about half of the gaseous material. Nevertheless, the remaining ' . -92- ammonia and hydrogen form a stable combination with mercury that decom- poses only at higher temperatures and after several hours. No correla- tion between the composition of the amalgam and the halts in the cooling curves could be established. It is difficult to assign an actual freez- ing temperature to 1 given amalgam from the appearance of the correepond- ing cooling curve. . ‘ The rate of cooling in most cases was much more rapid in this experi~ went than in the previous experiments, and the appearance of the curves varies somewhat depending on whether liquid nitrogen or Dry Ice-isOpropyi alcohol was used as a refrigerant. In general arrests appear in the cooling curves at higher temperatures on successive freezing and warming, and at times occur even above the freezing point of mercury. The shape of the cooling curves is perhaps more characteristic of a two component system in which solid solutions form than of a.system in which a eutectic composition exists. A eutectic halt produces a horizontal portion in the curve, but when two substances font a continuous series of solid solutions only breaks appear at the beginning and at the completion of freezing. Slope changes at temperatures between -60°C end ~75°C were observed in several of the cooling curves from this particular series of observations. However, the rate or cooling was much too rapid for equilibrium to be attained so the arrests in the cooling curves cannot be easily interpreted., -93- Conclusions flue cooling and warming curves for the system ammonium-mercury show that the system is more complex than that expected it monium forms an ideal solution in mercury. If the {rooming point of mercury was actually lowered by mnenim the depression was masked by the rise in temperature as e result of decomposition at the freezing temperature. The first freezing decomposes the upper phase of the amalgam extensively as observed by the volume of gas released during freezing, the contraction of the volume of the amalgam after freezing, and the tendency of the upper phase to disappear after the amalgam has been frozen and melted several times. Nevertheless, an appreciable concentration of amonimn was retained in the amalgam after a succession of freezings and meltings. The fact that many of the cooling curves exhibit definite changes in slope without a horizontal break in the vicinity of ~h1.5°c suggests that a solid solu- tion may form. Such a solution might well be a solution of some compound between amonim and mercury in mercury. The concentration of monium in the amalgams was so small that the possibility of the solutions exhibit- ing anything but ideal behavior might be thought unlikely; however, in the thermal analysis diagrams for sodium and potassium amalgams eutectica appear at concentrations of less than two atom per cent. The correspond- ing eutectic belt for sodium occurs at ~50°C and for potassium at 445°C. On seven cooling curves definite slope changes appeared between —50°C and -68°C while similar breaks appeared on six warming curves between -5130 and 423°C; no correlation was found between the appearance ~9h— _Q_mii of thee breaks and the {rowing temperature or the amalgam. These slope changes here not necessarily exhibited by successive warming and cooling curves. The rate or waning and cooling may have been such that a solid state transition did not always occur, so that one form of the solid was in a metastable state part of the time. .!.-'he possibility that these breaks appeared because thermal equilibrium was not attained during coolirm of the solid mixture must be considered. Equilibrium may not have been reached particularly in the experiments in which liquid nitro- gen was employed as a refrigerant and the rate of cooling was accordingly very rapid. 0n the otter hand under circumstances where equilibrium should have been reached; e.g. , when the rate or cooling was very slow as sheen in Figures 9 through 12 and when an amalgam was stirred during cooling, similar breaks appeared in the cooling curves. Comparable breaks were never observed when pure mercury was cooled down to the same low temperatures . ‘ 2 sw.__ No experiments have been performed which show whether or not monim amalgam is a colloidal dispersion or whether it contains a. colloidally dispersed solid. If I'ordinary" ammonium melgam were a colloidal diapereion or a froth of solid colloidal NH4+ng' particles in mercury then the cooling curves might be reasonable since the "true" analgan or compound phase would already be solid at higher temperatures and only the mercury phase would freeze at -30°C. Johnston and Ublmelohde31 found that the (already very high) surface tension of mercury is greatly lowered by the analgam which would then tend to concentrate in the interface to form a stable froth. -95- m. (mun! GBSMATIGB 0? cm BEHAVIOR 0! MORE}! MAMA}! WBODES Estorical Introduction Analgm electrodes have been the source or many interesting in.- voltigations. The standard electrode potentials of the alkali metals in aqueous solution were determined by a series or ingenious experiments by G. R. Lewis and his co-worherl using alkali metal electrodes .7h’75 '76’77 The reactivity of the alkali metals with water prevented direct measure- ment of the electrode potentials but Lewis determined the potential between the alkali metal and its emalgan in ethylamine or prepylemine solution of the metal ion, and subsequently determined the potential of the amalgam with respect to a standard electrode in an aqueous solution of the metal ion. The sum of the tan potentials was the standard oxi- dation potential of the alkali metal in aqueous solution. Date procured by Richards and Daniela78 from e.m.f. measurements of thallium amalgam concentration cells were used by Lewis and Randall” for computation of the activity of thallium in the smalgems. The electro- motive force produced by the concentration cell was 8 RT E -fiF-log 83 ’ where a; and ‘3' represented the activities of the metal solute in each amalgam electrode. Lewis and Randall demonstrated that for a concentra- tion cell in which one electrode was an amalgam of fixed mole fraction -96- 33' and the other was an amalgam of any mole fraction N3 the following expression related the electromotive force E to the concentration terms: a’ \ NF log 1?: =1 [ vb (my) I. 10% Na] + log 33' s From a plot of the term in brackets versus N3 the value of log 53' was calculated. At infinite dilution when N; a 0 and by definition log .3: = 0, log of 1: the intercept on the y-axis. Knowing cf, the activity of thallium in the reference malgam, Lewis and Randall calculated the activities of thallium and mercury in the amalgam of variable composition, and from this information the partial molal thermodynamic functions for each component. Richards and Conant80 made similar experiments and calculations for sodium amalgam concentration cells in aqueous solution, while Bent and Swift81 studied sodium amalgam concentration cells in d1- methylamine solutions. Bent and Forziatti82 measured the e.m.f. of a concentration cell in which one electrode was a very dilute sodium amalgam arm] the other electrode was a sodium amalgam of composition varying between 0 and 100 per cent sodium. In their plot of e.m.f. against concentration, plateaus appeared at the e.m.£. values corresponding to the compositions of the its mercurybsodium compounds predicted frOm Vanetone's phase diagram for the solid-liquid equilibria. 11 Coehn,13 and Smith16 on the reduc- The investigations of LeBlanc, ing properties of ammonium in the amalgam suggest that the oxidation potential or ammonium in aqueous solution is comparable to the alkali -97- metals. LeBlenc and Coehn also reported that the polarization properties of ammonium amalgam electrodes were characteristic of the alkali metal amalgama. Nérabezabé and Selatinayfl3 measured the electrode potential of ammonium amalgam at pressures up to 600 ahospherss in order to minimize decomposition. Their observations were made in aqueous solu- tion at 0° with a reference electrode of Hg(i)/ngar.(s),na,ar(aq). The potentials with respect to the hydrogen electrode calculated from observations made as soon as the cell was in operation were 1.80 I 0.10 v., but the electrode potential was not entirely stable even under high pressure and decreased to values as low as 4.75 volts within forty minutes. In Table XII appear the potentials of the alkali metal amalgam in aqueous solution which were reported by Lewis and his collaborators. The values for 2° would differ slightly from the vanes for ER since the concentrations are not those for the standard state. Instability of the potential of the ammonium amalgam electrode may be attributed to polarization by gaseous products from two different reactions! mg + H30 ~—> umon + 1/2 Ha NH, —-> NH, +1/2 Hz. The decomposition reaction should be suppressed at sufficiently low temperatures, as well as at high pressures, but the reaction of the amalgam with water is comparable to that of the alkali metal amalgams 7b which was observed by Lewis and Kreus and which interfered with their , ..1§§flMLKQ§i ":W ' 1.: ,,, , 4.:‘2' J— . .'..ah:.;"3”‘ TABLE III POTENTIALS OF THE MALI METAL WAKE} Ill AQUEOUS SOLUTION” . 1 E Electrode (With Respect to Hydrogen Electrode) Li magma“ (o.o350%)/L1*(1 N) K amalgam Na amalgam Rb amalgam (Unknown Concentration) / Rb*(1 N) (o.2216%)/K" (1 N) (0.20630/1122+ (1 N) +2.0720 v. 7 ' _ 41.8781 v. w +1.8673 v. +1.8h86 v. 1* Reported by Iuaawie'n"75 ’76177 and his collaborators. ** The composition of each analgam is given in atom per cent. -99- 0.3.2. measurements. The alkali metal ualgus were not attached mended rapidly. Lewi- end Irons overcme the problem by the use of \ inedietely by water but once hydrogen evolution bed begun the reaction ' e device comparable to s dropping electrode which continuously supplied a fresh surface of ensign to the electrolyte. Ithe viscosity of monium nelson made its passage through the capillary o! ouch an electrode in- teesiblo, so that in the present investigation stirring was relied upon to decrease polarization effects. Two types of experiments involving ammonium amalgam an an electrode were attempted. One experiment was an investigation of the relation between the concentration of ammonium in an amalgam and the potential of the amalgam with respect to a standard electrode; the other experiment was an unsuccessful attempt to measure the e.m.£. of a concentration cell consisting of two amalgam electrodes, The Effect of Ammonium Concentration on Electrode Potential All measurements were made at -30°G in a l N solution of monium chloride in 50% aqueous ethanol. Eloctromotive force use measured with a Leeds and Northrup Type K-2 Potentiometer. In order to record the e.m.f. a high impedance, which served as a filter to overcome the in. e r pedance of the cell, was placed in parallel with the recording potentiometer. W" A silver-silver chloride reference electrode was prepared by electrolyzing a silver wire anode in 1 normal potassium chloride solution for two hours ‘1 at one milliampere. An approximate value of o0.l95 volt for the -100- electrode potential of the silver chloride electrode with respect to the hydrogen electrode st 40°C in a 50% ethanol-voter mixture was obtained by extrapolation of data reported by Patterson and Feloing.83 the potential between pure mercury and the silver chloride electrode 1n- 40.0285 I 0.0005 volts. two different reactions might explain the behavior of the mercury electrode. In the chloride solution sufficient mercury may have dissolved to term a colonel electrode. The potential difference between such an electrode and the silver chloride electrode in an ethanol-water solution not saturated with colonel would not be the sane as the potential difference between a normal calomel electrode in water and a normal silver chloride electrode which is 40 .06 volts. In addition the potential between mercury and the silver-silver chloride electrode could be attributed to the deposition of amonim ions to form monim amalgan with the mercury. The potential of the mercury electrode when compared to the silver-silver chloride electrode did not change when amnonim amalgam was placed in the electrolyte. The potential of the malgam was negative with respect to both the silver chloride and the mercury electrodes. The effect of varying the monium concentration in the snalgems on the o.m.f. of the cell shown in Figure 22 was studied. The potential- time curves for smalgams which were warning from -30°C to room temperature were recorded on the electronic potentiometer, and similar data were recorded for analgans maintained at constant temperature. Curves l and 2 in Figure 23 show that the e.m.f. varied irregularly with time for -101- “if ”531% ‘p LECTROLYTE AMALGAM Figure 22, Cell for obtaining e.m.f.-concentration data for ammonium amalgam: electrolyte was 1 I ammonium chloride in 50% aqueous ethanol. -102- ..naggooammn Tooom... 28 .005: pm pqmamnoo wonwmsmp unsuahonsg .4 cam m 353.“ 330.? um: magmas» .N 28 .n “mewmdgm fiance—Ea you 30.3 Jug.» n 2:: .mm 95mg 99—522; 00— ON. 00 ow Om _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ N .. No 1¢.O \owxx 7%“th _ IOU A _ O _ n. . _ 10.0 S \l _ , ¢ J] 10.. H 4 _ _ 5/ _ 1N. W _ 0 m _ 3 w w.— tIs .slgus which were slowly warned to roan temperature while curves 3 all h lbw that the enuf. of the unalg-n attained a constant value in. the temperature was not varied. The initial reading in each case no that observed as soon as electrical connection was made between the «11 and the potentiometer circuit, and does not necessarily represent the nominal potential of the cell. Apparently concentration polarization was partially responsible for the decrease in e.m.f. with time as indi- cated by the large increase in potential immediately following stirring. The potential of a number of amalgame of different concentrations was measured at -30°C with the Type K-2 potentiometer. For each amalgam a series of potentiometer readings was made until the potential remained ’ ‘h constant, after which time the amalgam was immediately withdrawn from I the bottom of the cell into 0.3027 normal sulfuric acid and following decomposition was titrated with 0.22h6 normal sodium hydroxide. The data for these observations appear in Table XIII and suggest that the cell potential decreased as the ammonium concentration increased. The potential difference observed for many amalgame was approximately 1.30 volts with respect to the silver-silver chloride electrode and no values lower than 1.26 volts were observed, The experiment may be considered to be a study of the effect of monium concentration on the irreversibility of the amalgam electrode. High negative potentials approaching the value of the alkali metal amalgam electrodes were observed for extremely dilute analgame, and in certain cases where the initial potential of the cell was recorded -101;- MTRQ‘XOTIVE FORGE-GOIGMRATIW DATA ’ I new nu I ma momma mm m .3000 ' fiectrolyaia El .1? . Hillimolee Weight Moles Hole (3133‘) “if“ my Hz (me-J Hg Perxgent M Isa/1:301 s 4.82 0.00 321 1.60 0 V 5 -1.80 0.03 337 1.68 0.0018 10 -1.77 0.55 mo 2 .05 0.0268 1 10 -1 .77 1 .32 M? 2 .05 0 .0615 j 15 -1.70 0.311 301 1 . 50 0 .0560 - 30 -1.67 0.76 3h6 1.73 0.0th , 15 4.60 1 .56 1:27 2 .114 0.0729 K 60 -1.33 1.59 327 1.63 0.0975 3000 —1.32 1.61 381; 1.92 0.0839 60 -1 . 31 1.111 322 1.61 0.0707 ‘ g 25 -1.30 2.75 353 1.76 0.156 20 -1 .27 1 .614 330 1 .65 o .0991; 61 .1 .27 2 .01 31:3 1 .71 o .118 120 -1.26 2 .80 277 1.38 o .203 -105- electronically. The monium amalgam electrode was apparently most irreversible when the monium concentration was high, under which con- ditione a correspondingly large amount of gaseous decomposition products Valid accumulate at the electrode surface. A Concentration Call with Ammonium imalgsn Electrodes An attempt was made to procure data for amenium amalgam comparable to that obtained by Richards and Daniels78 for thallium amalgam concen- tration cells. The problem was not pursued to completion because the electrode appeared to be irreversible and the potentials fluctuated too widely. a cell was designed with compartments for two amalgam samples as shmm in Figure 2b, In the cold box an analgam was divided into two- portione of as nearly equal concentrations as possible and each portion was poured through a funnel into a compartment of the cell and covered with monium chloride electrolyte which had been cooled to about ~-3O°‘3. The cell was then immersed in a Dewar flask containing boiling Freon‘lZ at .3o°0, The platinum electrodes were placed in the two amalgaus and the silver chloride electrode was suspended in the electrolyte which was stirred with a motor driven stirrer. Measurements of the e.m,£. between each analgam and the silver-silver chloride electrode, as well as between the two analgama were made with the Leeds and Northrup Type K-Z Potentiometer. The potential between the two amalgams was never zero and was usually about 0.020 volts while the potentials with respect to ~10 6- |I|[ ELECTROLYTE mnlllll Ill Ii l'l AMALGAMS Figure 2b. Concentration cell with ammonium amalgam electrodes: electrolyte was 1 N ammonium chloride in 50% aqueOus ethanol; the diluted amalgam was placed in compartment A. tb silver chloride electrode varied within 2 0.05 volts or 1.27, the II. potential as was observed with many analgens in the previous weld-eat. Potentials above this value were never observed even when readings were made imadiately after stirring the analgesia with the platinum electrodes. After several hours the potential of the cell was Int constant and did not drift in s. particular direction but merely varied about the value-1.27 volts. One hundred grams of mercury which had been cooled to -30°G was added in 10 gram increments to the amalgam 1n compartment A of the cell. The potential or the diluted amalgam was never observed to differ appreciably from that of the original amalgam. '1: £- a result of the unsteedinees of tin potential a much greater dilution ‘ “Duld have been necessary to produce significant e.m.f. changes, and moZ‘eover, polarization and decomposition might completely obscure the 6tract. The compositions of the amalgam: were determined by the usual PrOcedure. The data procured from two series of measurements appear in Table m. From these experiments it can be concluded that an ammonium amalgam ll electrode rapidly becomes irreversible at -30°C in a 1 normal solution or amonimn chloride in aqueous ethanol. If polarization decreased the potential of the mnonium amalgam °l°Gtrode below the potential of the alkali metal amalgam electrodes one V ”ems justified in selecting the highest observed potential for ammonium t: analgm for comparisOn with the alkali metal amalgsms. The single °lectmde potential for ammonium analgam was computed using 0.20 volts i -108- ‘ J DATA FOR TWO CONCENTRATION CELLS WITH AMHQHIUH Afialflfifl ELECTRODES A! ~30°C Eon-Fe V8. Lg/AECJ' volts t -l .263 -1 .271: -l.26l -l.265 * fitter the addition of 100 grams of mercury. tor the silver chloride electrode potential and an estimated value or 0.2 for the activity of chloride ion in sexism-ethanol It ~39°G. For In alalzan electrode of concentration 0.0018 mole per cent ammonium the Single electrode potential was calculated: an. anal. (0,0018%) —> 11331 a meal) + e‘ .. .. ° ,_ (a ‘) m. 30°, 3013. anal.) E (an. anal.) mobs log flag.) Agcue) + a“ fi 125(0) + 01"(1 a mum). at 40°, E (AgCl) . 0.20 - 0.0h8 log (01"). E0811 =- Eula.l anal.) + E (legal) -l.80 volts. Ema, anal.) - 1.80 - 0.20 + 0.0138 log 0.2 - 1.57 volts. The potential, 1.5? volts, represents the potential of a 0.0018 mole per cent, or 9 x 10"‘5 molsl, solution of ammonium in mercury in a 1 N amonium chloride solution in aqueous ethanol at -30°C. The potential of a sodium amalgam of comparable concentration in a. l M sodium chloride solution in aqueous ethanol at -30°C was calculated from Lewis and Randall's data which appears in Table XII. The assumption was made that a l molal solu. tion of metal dissolved in mercury represents the standard state for an amalgam. 0.657,8h and an activity of 0.3 was assumed for sodium ion in aqueous ethanol at -30°c. The activity or a. l N sodimx chloride solution at 25°C is At 25°, E°(Na anal. 0.206%) . E(Na anal” 1 E 113,01) + 0.05? log "3+ We anal.) a 1.867 + 0.059 log 0:6 7;) 3 It. Li.- a", e .3? ‘3'? fr. . at ~30°, Rue all” 9 z 10")” - E°(!la anal.) . . 0.01:8 log 8‘; _ therefore, at ~30°, EOIa anal., 9 1 10°53») - 1.867 + 0.107 - 0.167 1 .. 1.80 volts. the value 1.80 volts for the electrode potential of the sodium amalgam is significantly higher than the value 1.5? volts for the ammonium amalgam under the sexes conditions, and suggests that even in the cell in which the potential was highest for an amalgam of known concentration the ammonium amalgam electrode was irreversible. Possibly this value ie not greatly in error since sodium amalgam reduces amenim ion to give monium analgan in a conventional method or preparing the amalgam. It I \ has been reported that this reaction goes essentially to completion.3‘h -111- VIII. cmssnnm or mourn: mm At 40% Theoretical Introduction In 1807 Seeley reported that amonim analgan was more compressible than mercury. In 1872 Routledge9 made some quantitative measurements of the volmne of the amalgan at various pressures up to about three atmos- pheres. The results or Routledge'e investigation indicate that the com- pressibility is slightly less than that emoted for a mixture of ammonia, hydrogen, and mercury. His experiments were carried out at room temperature, under which conditions the amalgam may have been largely a combination of gas and mercury as a result of decomposition. It was decided that a study of the compressibility of the liquid anslgam at a temperature low enough to minimize decomposition, and up to pressures at which the volume change per atmosphere is negligible, would give more information as to the composition of the amalgam. The compressibility of an amalgam which has been frozen and subsequently melted might differ from one which has never been frozen if some decomposition occurs on solidification. For this reason compressibility measurements on liquid amalgams which had previously been frozen were also planned. Isothermal compressibility is the change in volume per unit volume for a unit change in pressure at constant temperature, and is defined by the equation , l (— 3 v) fl v0 5—5 ~112- h when 7. is the initial volume, and V is the volume measured at pressure P. compressibility is determined with an apparatus, called a planet», by scanning the volume as increasingly large pressures are carted on s ample of the material under study. At room temperature and relatively low pressures gases have measurable compressibilities, but most liquids and solids require several hxmdred auuospheres' pressure to produce a significant volume change. A piezometer frequently employed so} compressibility measurements on fluids consists of a large bulb for the ample to which is attached a capillary containing mercury. The change in the height of the mercury column as pressure is applied provides a measure of the volume change of the fluid. The apparatus containing a sample may be placed inside a pressure chamber and subjected to the pressure of an hydraulic press. The external and internal pressures on the glass apparatus are equal so that the danger of breaking the glass apparatus is eliminated. For investigations in which the pressure is low enough for the piesometer to withstand, the pressure may be applied by an air pump to the mercury in the capillary. Suitable variations of these methods were used in determining the compressibilities of many liquids and solutions, particularly by '1'. W. Richards and his collabora- tors.85 The most recent measurements of compressibility on systems comparable to anmonium amalgam were made on liquid metals by an ultra- sonics method. The velocity of sound in a substance is related to ice. thermal compressibility according to the following expression inborn V5 is the initial volume, and V is the volume measured at inmsssure P. Compressibility is determined with an apparatus, called a pissometer, by measuring the volume as increasingly large pressures we exerted on a staple of the material under study. At room temperature sari relatively low pressures gases have measurable compressibilities, that most liquids and solids require several hundred atmospheres' pressure to produce a significant volume change. A piezometer frequently employed fibr cempressibility measurements on fluids consists of a large bulb for the sample to which is attached a capillary containing mercury. The change in the height of the mercury column as pressure is applied provides a measure of the volume change of the fluid. The apparatus containing a sample may be placed inside a pressure chamber and subjected to the pressure of an hydraulic press. The external and internal pressures on the glass apparatus are equal so that the danger of breaking the glass apparatus is eliminated. For investigations in which the pressure is low enough for the piezometer to withstand, the pressure may be applied by an air pump to the mercury in the capillary. Suitable variations of these methods were used in detenmining the compressibilities of many liquids and solutions, particularly by T. W. Richards and his collaborae tors,85 The most recent measurements of compressibility on systems comparable to ammonium amalgam were made on liquid metals by an ultra- sonics method. The velocity of sound in a substance is related to iso— thermal compressibility according to the following expression Cp fl=/;5‘fia‘c; -113 .. “filth-Mitystthsnbstm,sisthsvslssitys£sm umm,~m%uturaueummn capacities.“ apparatus thither ultrmsiss equipment nor an hydraulic press were "my available) therefore, a simpler device was devised {or the investigation of the compressibility or mains ensign. If an amalgam staple eon- tsins entrapped gas the volume simld change significantly shes subjected to pressures of a tee atmospheres; otheruise it should be relatively incompressible at such low pressures. In order to determine the presence or absence of entrwd gas the apparatus illustrated in Figure 25 was designed for snorting low pressures on an amalgam sample at -30°C, the taperatura of boiling Freon-12. Pressure is {me per unit area and may be represented by the expression in which p is pressure, 1' is force, I is the cross-sectional area over finish the force is applied, and mg is the weight of mass s under the influence of gravitational acceleration g. In the piesomster designed for measuring the compressibility of mnima analgem pressures above one atmosphere were produced by the weight of a column of mercury acting on an amalgam sample of uniform crossnsection area. The height of the mercury column was the same as the lower level of the sample when the applied pressure was the pressure of the ataosphere, and higher pressures ’u‘” ‘ .1 SAMPLE TUBE PRESSURE WHEN THE MERCURY IS THIS LEVEL IS THAT OF ATMOSPHERE Figure 25. Apparatus for studying the compressibility of ammonium amalgam. W'- "N‘wrvv “w - l v 1 “I! obtained by the addition of weighed quantities of mercury of the coin-I. the weight of mercury which exerted one ntuoephere or procure on th- ouple m the weight in gram of a column of mercury which had a memectionel area, in square centimeters equal to that of the sample “In, and was 76.0 cm. high under standard conditions of temperature and pres-um. 'the pressure in atmospheres exerted on the anelgem in the apparatus W88 1 + PH; where P38 is the pressure exerted by the mercury 001mm above the one atmoephere level. With the application of pressure to the sample a volume of mercury equal to the decrease in volume 01‘ the amalgam entered the sample tube from the reservoir. The volume of the anelgm sample was calculated at each pressure by measurement of the height of the mercury in the column before and after a given increment of pressure was applied to the sample. 1.. cathetometer was used to determine the level of the mercury within 1' 0.005 cm. The volume of mercury entering the sample tube vac AV - Fr,“ Ah - 8.1Ah, where r; is 1.55 cm., the radius of the reservoir column, and A h is the change in the height of the mercury in this column. The original volume of the amalgam V0 is calculated from the volume of the sample tube, so that the volume at any pressure is Vo - VP, The piezometer, Figure 25, was constructed in the glee: shop from heavy walled Pyrex tubing. is protection against leakage stopcock retainers were employed and a rubber stepper wee wedged tightly into the —116- ban ad socket Joint clap to prevent it from opening readily. A piece 01' 33: II. o.d. tubing was titted over a rubber stopper Just above the W stopcock to provide a means for keeping the sample at o30°6 with c boon-‘12 cooling bath. Melted paraffin was poured around the stopper inside the 323191: to prevent leaking of the refrigerant. The piezometer was uoured firmly by means of clamps to a vacuum rack. That part of the apparatus from the spherical joint to the two-way stopcock was the sample tube. A glass seal was made just above the stop- cock, which means that the crosseeotional area of the tube was not uniform throughout. For this reason a weighed mount of mercury, on the order of 35 grams, was poured in the tube before the amalgam was intro- duced. The weight of mercury added to the tube varied somewhat with each series of measurements and likewise the initial volume of amalgam varied, as well as the initial height of the mercury column. The volume of the sample tube was calculated from the weight and density of the amount of mercury required to fill it. The mean value of four weighings of the mercury contained in the tube is 153.2 grms. _ weight of mercury _ 13.2 9. Volume or tube density of mercury 13. gms. , Volume of sample - volume of tube - volume of mercury necessary to cover seal. Experimental Procedure Before each series of measurements mercury was poured through the sample tube into the pressure column until the level was that of the top -117- of the sanple tube. That level in the pressure column corresponds to about one atosphara of pressure, the exact value or which was obtained has a barometer reading. The mercury was drained from the sample tube by the proper change of the stopcock which was then closed to both chambers and never moved again until a measurement was made on some amalgam. Air was rmved from the mercury in the pressure oolum by carefully heating the area, containing mercury with a Bunsen burner and simultaneously pumping on the column. A weighed quantity of mercury sufficient to cover the non-uniform area. was poured into the sample tube and the level was measured with the cathetometer. The mercury to be added to the column in portions corresponding to the desired pressures was weighed. The first weighed portion of mercury was carefully poured into the column and the air bubbles removed by pumping. The cooling jacket was filled with Freon-12 about ten minutes before the amalgam was introduced into the apparatus. Amalgam which had been prepared and washed in the usual way was put into a Pyrex tube in 3 Dover flask containing Freon-12 for five minutes and then transferred to the ample tube of the apparatus. With the two- way stopcock still closed and the one-way stepcock open the height of the mercury in the column was measured with the cathetometer. Pressure was applied to the amalgam by opening the two-way stopcock to the mercury column and again the level of the mercury was determined with the cathetometer. With the stopcock closed to the pressure column another weighed portion of mercury was added and the effect of this additional pressure on the volume likewise measured. In this manner about three -11 8- “spheres of pressure could be applied to the sample. Even at the higher pressures the more concentrated malgass retained a frothy appearance as if gas were entrapped. When a pressure was reached at \ winch the sample volume did not change upon two successive additions of mercury to the column, observations were discontinued. The sample was removed from the tube into a solution of 0.0517 R sulfuric acid by first i opening the ten-way stepoock and than removing the cap from the tube. ' ‘ A definite odor of monia was apparent when the cap was removed. The excess acid was titrated with 0.0379 N sodium hydroxide in the usual way. The mercury from the decomposed sunelgem was rinsed, dried, and weighed. To remove the mercury from the apparatus a glass tube with a spericel connection was clamped to the tap of the sample container. This attaclment was bent so that mercury would run from the pressure column into the sample container and out of the apparatus into a bottle. Some mercury always remained in the apparatus but no more than that supported by the weight of the atmosphere. By the method described compressibility data were obtained for two smples of pure mercury at room temperature and for five different malgem samples which were never at temperatures below -30°C. In addition samples of two of the five amalgams were placed in e Pyrex tube, imersed in liquid air for an hour, and melted in a Freon-12 bath at 40°C, Volume—pressure data were then taken for these two samples. No changes Si appeared in the volume of the pure mercury samples as pressure was ‘ E applied. i -ll9- - f I n . I . n a . I . - .. ‘ Celmzletions end Results beta for the volume-pressure measurements of mercury and the ensign-s weer in Table XV end Figure 26. Detsiled calculations for -elgn' V are as follows: Uncorrected barometer reading at 27°C - 73.80 cm. Correction to 0°C for expansion of the brass scale and of the mercury - -0.32 cm. Correction of sea. level from altitude 860 ft. and latitude 132° ' '0 s02 ““071 Corrected barometer reading - 73.&) - 0.32 - 0.02 I 73.16 cm. Pressure in atmospheres - ;%‘%8 atm. - 0.967 atm. The pressure exerted on the sample when the volume is V0 is 0,967 atln. V0 - volume of tube - weight of mercury covering seal/ density of mercury at 2 C. Vo - 11.31 m1. -%°-2§-%-751 -8.15 ml. The pressure on the sample at any time - P .. Pa + P , where P3 is atmospheric pressure and g5 pressure due to the mercury in the column. P33 is t P; - 73.116 + 66.33 mm. ' 139.811 cm. - 1.81; atm. P3 - P1 + 12.93 - 152.77 cm. - 2,0 etm. A h; - difference in cathetometer readings - 0.26 cm. An - nrfah; - 8.1x0.26 - 2.1m1. v1 :1 v0.- Av; - 8.2ml.-2.lml. -6.1ml. V; 1' V1- Ava " 6.1-0.3 = 5.81111. By this same procedure all other volumes and pressures for this series of observations were computed. V0 was calculated from the weight and ,9! TABLE 17 mamas-801m DEA m A 001228381311.er 3WD! 0! mm W file P 1" it otller Ah AV $05. 0? I (03.33) (ate. Erased $11 (078.) (ml.) Alleluia a.) £95.) (£1.21. 1‘ I 78.38 0.978 8.11 _ . 1 .8 1.78 2. 2 25 0.32 2.6 5.8 I 7 .1 1.85 8.91 8.82 0.08 0.6 5.2 i 1117.1 1.95 15. 15.80 0.05 0.1; 11.8 I x’ 1511 3 2.03 22.11 22.06 0.05 0.1: 8.1; § 1 161 o 2.12 28.78 28.71: 0.01. 0.3 11.1 - " 167 7 2.21 35 .80 35.35 0.05 0.1: 3.7 i 180.9 2.38 178.55 118.53 0.02 0.2 3.5 r . 2.116 55 .10 55 .10 o 00 0.0 3.5 E 11 78.1: 0.978 8.7 135.1 .78 2.12 2.39 0.03 0.2 8.5 . j ' . . 1.87 9.06 9.05 0.01 0.1 8.1 1h8.3 1.95 15 a. 61 0.00 0.0 8.1. l 151.9 2.01; 22.22 22 22 0.00 0.0 8.1; . - - ; III 78.8 0.978 8.11 1111.2 1.8 8.95 8.86 0.07 0.6 7.8 167 .5 2 .20 35 .19 35 .16 0 .03 O .2 7 .6 , 2 37 118.13 118.10 0.03 0.2 7.h i 193.5 2 55 61.26 61.26 0.00 0.0 7.1. 17 78.1: 0.978 8.0 1110.6 1. 8.37 8.37 0.“) 0.0 8.0 153.9 2.02 21.67 21.62 0.05 0.1: 7.6 167.1 2 20 311.87 38.87 0.02 0.2 7.11 180.2 2 37 87 .93 117.93 0.00 0.0 7.8 v 73.5 0.967 8.2 139.8 1.81: 8.31 8.05 0.26 2.1 6.1 152 8 2.01 21.28 21.20 0.08 0.3 5.8 166 o 2 18 38.119 0.05 0.8 5.1: l 179 1 2.36 147.57 87 57 0.00 0.0 5,1. 192.3 2.52 60.80 0.00 0.0 5.1 VI 73.8 0.972 8.3 138.1 1 .76 1.75 1 .61 0.1L 1 .1 7 .2 110.5 1.85 8.20 8.13 0.07 0.6 6.6 153.8 2.02 21.52 21.18 0.01. 0.3 6,3 167.1 2.20 311.75 38.73 0.02 0.2 6.1 180.0 2.37 .71 117.71 0.00 0.0 6.1 193.2 2.514 60.88 60.88 0.00 0.0 6.1 VII 73.8 0.972 9.0 135 .0 1.78 1.52 1.118 0.011 0.3 8,7 181,6 1.87 8 05 8.03 0.02 0.2 8.5 1524.8 2.01. 21 27 21.26 0.01 0.1 8.1 168.1 2.21 3h 58 38.58 0.00 0.1 8.11 181.3 2.38 h? 76 h? .76 0.00 0.0 8,). J ‘ l2’ IO- 0 g 11 9 SM 6 9. o In 8' D I2: E’ D o A. 0 :1 Ill 0 In —J i o O “-16- O 0 O O m 2 o o :3 4 o o o o 1' g e 0 4_ o G o o I 2- O I l _ | I J | l.5 2 2.5 3 PRESSURE (ATM.) Figure 26. Volume-pres'aure data at _300 for six ammonium analgams .f; of varying composition; Sample I, 0; Sample II, X; Sample III,o; 5‘ Sample Iv, a; Sample v,e; Sample 111,9; Sample 1711,. , I l -122- —‘- dluity of mercury which ere known to tour eignifiomt figure-1 therefore, 1n the. measurements the inaccuracy of Va depends only on A v which in turn depends on the aconrecy with which A h was measured. The difference A n batman m cethetoneter reading: 1. accurate to t 0.01 on. which llhctheemrin Av A(Av) - 0.01 nu,“ . o.1ul. The voltmeo are listed with only two significant times and are accurate ‘0 1' 0.1 ml. which introduces a maximum error of three per cent for volume: at higher pressures for amalgam sample I. In most cases the volume ie in error by only one and one-half per cent. Results of the data for computing the density and composition of the “algae appear in Table XVI. The weight of an amalgam is essentially the weight of the mercury in the amalgam. The weight of mercury added to the sample tube to cover the glass seal and the weight of the mercury which entered the sample from the reservoir during compression were sub- tracted from the weight of mercury remaining after decomposition of the analgem. Following are exemplary calculations necessary to complete the data for amalgam v in Table xvn Weight of mercury which entered the sample tube during compression in (V0 - Vfinal)Hg - 2.8 ml. x 13.6 gum/ml, :- 38 an. Weight of mercury added to cover glass seal - 143.2 911, Weight of amalgam -= 116 - ’43 - 38 ' 35 gm. Density of amalgam - weight of mercury/sample volume . 35.1/8.15 ' h.3l gm./ml. #86 2.8.0 8m.o «in d; 3H o 0.0 mém m.mm~ HE $0.0 Q6 36 o.m md m. on a.“ o6: afifl E mmd 3.0 3.0 n3 «6 mm mm m.m «.3 mod... p «8.0 3.0.0 8m.o Qua mm.» 9: m o.o 0.2 15 E . 30.0 38.0 3.0 «a “3 mm 3 0A ham tame HHH New 430.0 08.0 2&6 «.3 $5 43 4 m6 dom :3 HH od pod 8.0 and 44» m mo m3 o.om 5.3 H £2 £2 um figémv 6H3 ammfiw: flame > dds :3 fifiw 28 com 33: no 5328 253» fl 5 doom L55 395m 5 m 302 ASHE $32 Emflofi Seam mm «o :5 mm co #3 > .. o> mm mo .23 mm mo .5; gouge 5.5”“ng mg «8.3 gammmmmvfio mug.» mom $30.25* ho ZOMBHmomvSo E mummy. Hole r cent of mania in the amalgam - (moles Elk/moles lg) ° 100$) - 0.35 mole per cent. Iron rigors 26 it appears that the very concentrated nelgms are Met lore compressible than the dilute melgme. Amalgam II and II, which are couples I and III after freezing, retain slight compulsi— bility end only a wall concentration or monium. The weight and density of the mercury recovered from each decomposed amalgam were used to calculate the volume occupied by the mercury alone. See Table XVII. If the difference between the volume of the analgem and the volume of the mercury represents a volume of annonia and hydrogen 8“ entrapped in the analgam, then the compressibility of this volume Should be the some as that of a combination of ammonia and hydrogen gas in a 2:1 mole ratio. The volume increase over that of pure mercury for analgem VI was considered to be V0. Employing the same A v‘s as in Table xv the volume was computed at each pressure for amalgam VI, and these data plotted as points on Figure 27. Actually the points plotted in Figure 27 are identical to those for amalgam VI in Figure 26 except for their positions with respect to the volume axis. The molar volumes of ammonia and hydrogen at -30°C and at each half atmosphere of pressure between one and three atmospheres were computed. For calaulatiou of the molar volume of mania two terms or the Beettie- Bridgman equation were employed in conjunction with the re-evelueted I ' 87 Beanie-Bridgman constants of Max-on and Turnbull. The part or the 1 1 . S“ Beattie-Bridgnenn equation used here was P a g3 + [Q 425— i . ¥éz —126- .,.w. do: «m6 ‘ do o.m $6 3H, E fin .. a.» o.m m6 . , «ma Q42. K S. 3 gm «6 .8.“ dmn p «to. 26 m6 . 06 m.» 03 E do. 04 . HA :6 3. a an a." o in n6 law mad 43 HH a? mm «5 i3 36 w H Jay E. 35 35 33 “.3 in: flew-walla and“ menu? Egg Mummy»? wwomeOmm 395 E on as?» enhance :3» 25%» 0.5%» 25o» we no 5% maeem egg EOE ho Enos» mam. mg kg a: EOE «Hg .3 wage.» a; .mo zaggu 4 HS ".134 a 0) (ML) VOLUME n l ‘ L5 2 25 3 PRESSURE (ATM) Figure 27. Volume-pressure relationship at -°O°C. for a volume of ammonia and hydrogen equal to the difference between the volume of amalgam VI and the volume of mercury in amalgam VI: the points represent experimental values; the curve represents ideal gas behavior. —127- where fl for ammonia has the value of -3.291. The molar volume of ammonia at 1 atmosphere and ot -30°C is V1 . -RT 1 /RB'I'2 -32“ x 3.291 x P7 _ 19.8 liters the Scottie—Bridges equation could not be expected to apply to mania it. pressures shove 1 e’euosphers and st ~3o°c, which is only 3° above its boiling point, but no better corrections were available in the literature. Molar volmnes for hydrogen were calculated from the ideal gas law. .the combined volume occupied by oneohalf mole of hydrogen and one mole of amenie was evaluated for each pressure. In Table XVIII are listed the volumes in milliliters which would be occupied at each pressure by the mania. and hydrogen in each amalgam if all the monie and hydrogen were in the gaseous state. The pressure-volmne curve for amalgam VI in Figure 27 was plotted from the data in Table XVIII. A comparison of the curves for the gaseous mixture with the pressure-volume data shows that the initial volume of some of the smelgsms is not as large as the volume would be if all the ammonia and hydrogen contained by them were in the gaseous state, but that the change in volume with pressure is greater than for the gaseous mixture. Discussion It all the ammonia and hydrogen were combined with mercury in the amalgam, the amalgam should have been much less compressible than a ' perfect gas. The data show that the amalgam at the pressures for which -128-- TABLE XVIII VOLUME OCCUPIED BY GASEOUS AMMONIA AND HYDROGEN IN EACH AMI-LGfiM AT ~30° P Holer Volume of NH3 and— H; (1111.) (stun) Volume NH3' ,+ 1/2H2 I II III Iv v VI VII (liters) 1 .0 29.7 29 2 .b 1.0 0 .h? 19 8 .9 0.53 1.5 18.9 1.15 0.7 0.30 12 5.9 0.130 2.0 1h.8 1h.2 1.1 0.5 0.21: 9.3 bi: 0.26 2.5 11.7 11.1 0.9 0.11 0.20 7.1L 3.b 0.20 3,0 9.8 9.1: 0.75 0.33 0.16 6.2 2.9 0.17 (Concentration NH‘ 1 in millimolss) 0.96 0.761; 0.0310 0,016 0,63 0.30 0.0177 nonsurlnents were obtained sure more compressible than an essentially sexiest gas. Only an imperfect gas is more compressible than a perfect one, thicknesses that ammonia use doubtlessly being liquified during the compression at ~ ’°C. The assumption was made that all the ammonia present in an amalgam use compressed by the exertion or 1.5 atmospheres on a sample and that hydrogen behaved as a perfect gas, so that 1.5 atmospheres' pressure reduced its volume to onsethird of the original volume. If this assumption was true then the following expression in which “0(n33) and v°(H§) represent initial volumes applies: v°(NH3) ” ”3 v"(213) ' V2.5 stun. ’ v1 am. If each ammonium radical dissociates into one molecule of smmonia.and one atom of hydrogen then v0(run) ‘ ”0012) , and 2V0(H2) + 2/3 v°(Ha) a v2.5 atm. * vl atm. ' The preceding relation was used to calculate the initial volume of hydrogen from which the total initial volume of gaseous material present was computed. The difference between the volume of amalgam in the tube and the original volume of gas was then the actual volume occupied by an amalgam in which no gas was entrapped. -130- Data from these calculations appear in Table III. Using the corrected initial volume and the weight of mercury in the sample as the weight of the amalgam the density of each amalgam at one atmosphere containing no gas entrapped was computed and listed in the last column or the table. The density or pure mercury in 13.56 gm./ml. at -3o°c. For all the dilute amalgam the corrected density corresponded to mercury, but for the concentrated malgms was less than that of mercury. The large difference in the actual volume or the analgsm and the volume that would be occupied if all the ammonia and hydrogen were in the gaseous state establishes that monixm, hydrogen, and mercury are combined in some way in common amalgam. Only a few compressibility measurements were made and those were in a narrow range of pressures, but the information gained was sufficient to show that at ~30°C the amalgln contains ammonia which can be liquefied, and must also contain amonium in combination with mercury. -131- o. in 03” m.m o.m 00.0 42.0 mm.o 0.0. HH> ode mp m.m m6 m.~ 84 8.0 NN H» 4H.» mm m.: «6 m.m ~.N a...“ md > fima 8H mé o.m 3.0 and mud 9m pH m. m mm m. 5 :6 4H. H on. 0 mm. o o...” HHH o. 9 fie :5 56 Rd 2.0 3.0 m. o H $6 fie m4. :6 m.m $8 £J mm: H Facing :3 he“? chews? new no Aesop QN hpfimnca mm no no mean; no mesa; mend—Hg Suwanee fl 33880 232,, esoofioo H335 Hagen 25; 33; + 3:30» Macaomm ZOHBngSnHQ mpommwa mo acfimflmm um; mom 598550 meAdE‘ 232.0224 .8 Ewan Mme a mama. -132— some: Following an investigation of several methods for preparing and handling monim amalgm, an electrolytic preparation was adopted, and a means for purifying and manipulating the amalgam at temperatures in the vicinity of —30°C was devised. Acid extraction of the ammonia from the decomposing amalgam provided a means for analyzing samples of the amalgam. In most cases the amalgams on which measurements were made contained less than 0.50 mole per cent of ammonium. Kegnetic susceptibility measurements by the Gouy method at ~3o°c gave evidence that ammonia and hydrogen were combined with mercury in a way which decreased the freedom of electrons in mercury. Values as large as —O.270 x 10" c.g.s.units/gm. were observed for the specific suscepti- bility of the amalgam as compared to ~0.167 x 10-. c.g.s. units/gm. for the specific susceptibility of mercury. The large increase in the diamagnetiam of mercury to which only a small amount of ammonium had been added established that uncombined ung- radicals comparable to alkali metal atoms were not present in the amalgam. Apparently the amalgam is an entity of the type NH4+ng“ in which the few electrons furnished by ammonium to mercury suffice to remove the temperature independent para~ magnetism of mercury. Failure to find a relationship between the compo~ sition and the density of the amalgam suggests that the amalgam is partially decOmpoeed at -30°C and contains ammonia and hydrogen gases entrapped in the mercury as well as some ammonium in solution in, or in -133- combination with mercury. The amalgam ordinarily studied thus appears to be a um" containing gaseous decomposition products. A study of the solid-liquid equilibrie in the system ammonium» mercury shoved that about 601 of the ammonia and hydrogen present in the mercury were released during a single freesing and that the decomposition produced by additional freesings was insignificant, although an appreci- able quantity of ammonium remained in the mercury. This indicated that some ammonia.and hydrogen are very loosely bound to mercury in the amalgam perhaps as entrapped gas and that the remainder is present as monim or a compound of mercury with monium. The amalgan or possibly a stable froth containing the amalgam floats on top of mercury as indi- cated from cooling curves obtained simultaneously for each phase of the amalgam in which the cooling curve of the lower phase was not signifi— cantly different from that of pure mercury. From the cooling curves it was observed that during the solidification process the temperature of the system increased slightly perhaps as a result of the breaking of some type of bond between the components of the system. Definite frees- ing temperatures were not obvious from the cooling curves for the amalgam, although the shape of the curves was reminiscent of solid solu— tion formation. If the I’true" amalgam exists as a colloidal dispersion or a froth of colloidal particles in mercury than the freezing curves would be reasonable since only the mercury would freeze at -ho°c; the fusion point of the amalgam would be higher than -hO°C. Ammonium amalgam electrodes were found to be largely irreversible in aqueous ethanol solution at ~30°C, although a value of 1.57%volts 431.- f—_—_ for the potential of an amalgam electrode in solution with monies: ions was conputed. 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Conway, Electrochemical Date, Elsevier Publishing 00., New York, 1952. -l39- 85. 1’. fl. Brim-n rho Physics of High Pro-sures, a. 3011 and Sons, m” Damion, i931. 86. o. a. Klopps, 4. Chan. Pm. 11, 668 (191.9). 57. s. a. ham and n. Turnbull, Ind. Eng. Cram” 2;, has (191:1). \ 4.110- (1,"‘11': ' 1293“ -Due Demco-293 “A ————-__ WY 1.1mm ‘IICIGAN STQTE UNIV. LIBRRRIES ‘ WWWI"!HIIIWIWIHIWHIWHIIWIHW\l 312931.7142501