SOME METHODS FOE THE DETERMINATION OF THAIilDM t j.. ±sy Ramon Frederick Rolf A TfHSIS Submitted to the School for Advanced Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHXLQSGPHI Department of Chemistry 1 95 6 ProQuest Number: 10008512 All rights reserved INFORM ATION TO ALL USERS The quality o f this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete m anuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 10008512 Published by ProQuest LLC (2016). Copyright of the Dissertation is held by the Author. All rights reserved. This w ork is protected against unauthorized copying under Title 17, United States Code Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Mi 4 8 1 0 6 - 1346 ACKKOWLEIXMENT The author wishes to express his gratitude to Dr, KLmer Lelninger for hi® direction and counsel throughout this work. Appreciation is also esctended to the author1® wife, Dorothy Fay, who helped In the preparation of this manuscript. 11 86M8 fctl yxg w yggMTBAyrftn op % -ISElCShSk^^ H $ ABSTEAS^ lie partinl Sl^y^SldbiSttsit -of the .|Piw^ii^iMS®nr1^ "jA/^,|ti^ A4 rftftiMiiiWtaiM. jajk 3 P8HP wKtkN.A Pk-. j& W^lIL^ jtWI wbK nw w s w n wwito ify «K%»1Mm w c «W*av3 r FiX T«W 19$& IirW KHHW niKM fflHliiiliriiiW jiW !»HW «iW >*iyi?tfiiBfi|Trr;g^gj^)»-i| ft# ft^X©©© ft698@8fcft # ftftftlft# itn ft ^#8®S#feft:* ft ftftt&Sft^t lift Jft# ftteft ft# ' If^ffffifofflftt ffilft JttftftiSftl ft# ftjf jjft ft$ ' ftftft 'Sl33SftftftBBtil ft# ' i ^i^-i*^ n ( x x x ^ ft© ^ y |yr!jij^ i)| i[ i f tjf ftfo # ftlSftftS Haft’S ft #01* ftlm ) M ft'ls# f t 'W ^ ftn ftftis is . ft# Iftftfftll 3Pft^fe||#bft#: * ^Ehft ISftftftlft® ^P^:1"^ ftfc&ftftlSSftlftii fftteiaftft# fttaftftft us siNWft^i ftss#ft^ ft# (MU jpftf ftMl #ft# 3© I# 01# ftHM** 0P|^ ftftft^Sift# ft# ftfilftXlllEI8ftftfttUft ftftft fliCT^ ftS3>$ft# Sllftftftft m MK W p «aw»r ef 0,3 jmuf «(«*• #m ^tm^Timii ( I ) , fttrft Th« 4 ir*o t H IW Jft# Hift ftiftftiftlsslSftft ft# i» bWMd on « » «3Hnate« toddtUtm » f tto ttte a ( i ) to t^taaisut ( IK ) v ita i bype*aWB»4ta» fh« t^patmMilte la w&mM&etd ftjM ftftftWBpjt P^Ww*^r!lPifW *W Br?w5^ ’ fereriaf ^il[ tBu» #fetu8^• f «w aiapi»MtHftft l^ ^Ml t ftm ft ft *•^h•w fiin tX af__t.t.. .. iuw i*rw „,„f ;..tS w ^f -■■ -■f wrt ^ww tinl iii «. ,. .... (I) atiatta vtmtMMms * w«31 m*mto of teo^to i«n. tm ®ea» so l2ir*3., S. oad MmmOtw, 0.» 2* aworg, Chan., 1S3, S7& (1926). tv iHiHiMAttijNtt&'fbtiiAji && nMi^§|g|ggfc fTl tft 4&utf%*iy|ftMK f«ffisM '£j| % % # ty-mtf %St ftj$ *$1 IHitlfti. 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E* F, S T O R I C A L . .......... 3 Cbcid&tlon of thallium (1) to thallium (III)*. m m Reduction of Thallium (HI) to Thallium (I).*♦;***♦***.*♦•* Volumetric Methods for T h a l l i u m * Gravimetric Determinations of Thallium*.................... Trace Methods.*,****.*..♦*♦***,**#****««**.**.•«•«••*...... Metallic Redactors*****•**«.*••*****•*«.««••***»*****«*.*•• EXPMIMENtAL ******..... *.... X Standard Solutions......................................... H Stability Studies of Sodium %pochlorite Solutions.*..****. XIX The Use of Metallic Redactors for the Reduction of Thallium (XXX) to Thallium (X)*.****.***..*♦*........... A* Cadmium Redactor**..****.#*...*.****.#.**************•** B* Silver Eeductor**«*••„*•,#.***•«**••*.*••«»«*••*««•**•«* C, Bismuth Redactor•.•...,•**,••*«••.*••*•••*••»«••*».•**•* B* Nickel Reductor*•••••••••,.••*«»•*«**.«;•«•.**•,*••*••** S* Lead Redactor****•*.*•**••.»•*#*•,*.«•«••*.*.•««•»••**•* F. Aluminum R e d u c t o r G* Zinc Reductor.*,.•***.,•**•**•*•••***••*•**•»•;•..... H* Amalgamated Zinc Redactor.****.»•**•*,•****•*.•****;•»•* X* Cadmium Amalgam*********^*****.•*•.*****•*•**•*•*«*»*.*« J. Lead Amalgam •«•»;««.*•••*;«**••*•;«****•*•***** K* Bismuth Amalgam*****..•****;***.***•#****.»»*•**........ L. Discussion* •«***••* *...... .........****** **......... I? Volumetric Determination of Thallium (I) Using a Standard Sodium hypochlorite Solution. .... Am Direct Method ..... • . 1. Salt Effect.****,*••****•***,*.•***•*............. 2. pH Effect ..... 3. Effect of Sodium Bicarbonate Concentration........ km Effect of Bromide Xon Concentration.•*•«•*.••••«•. 5* Determination of Thallium. .... 6m Determination of Thallium (I) After Using Metallic Redactors***.......................... B. Indirect Method*****,*».•••«**.**••.*•*•*...*••.•«•••*** 1. Tim© Required for Oxidation of Thallium (X) by Excess Hypochlorite............................ vi 1 3 3 5 9 12 13 16 16 18 23 27 28 31 32 3U 35 36 37 38 38 35 bX hS L5 U5 1*6 U7 U8 h9 51 52 53 Page TABLE OP CONTESTS - Continued 2* Determination of Thallium (I).*..................... 3. Determination of Thallium (I) After Using Metallic Redactors............................... C. D i s c u s s i o n * * **•**.. V Gravimetric Determination of Thallium Using Sodium Ifypochlorlte...................•***•«***•**».*•**.*••**»•< A* Mbshimg the Precipitate*.................................. 3. Effect of Hydroxide Concentration.•....................... 0. Interferences ..... D. Effect of Drying Conditions............................... E. Discussion. ......................... ••• •»«••.....#« VI Improvements on the Precipitation of Thallium (IH) Oxide by Potassium Ferricyanid®.***, ... A* Effect of Precipitation from Hot Solution and Digestion of the P r e c i p i t a t e . . * * ...... 3. I n t e r f e r e n c e s 0. Contamination of the Precipitate by Potassium Ferrieyanlde***#•»*«****»»••*«•*#«»•**«.•*+***•*.*#*♦*♦ D. Discussion.*** .... SUMMARY .... 53 $k 56 60 61 62 65 65 65 69 70 72 73 75 77 LITERATURE CITED ....... *.*.* 19 vii INTRODUCTION 1 A large number of volumetric methods hare been proposed for the determination of thallium ehila relatively few gravimetric methods have been proposed* Hoot of the methods require a preliminary reduction of thallium (HI) so that all the thallium i d i be present in the plus one oxidation state*' Sulfur dioxide is acmmxLy need m the reducing agent# Warn thallium Is to be determined by volwetrio oxidation, sulfur dioxide has several disadvantages as a reducing agent,- Since metallic redactors are more ©canrenAent as reducing agents, a study of the reduction of thallium (11$ by metallic reductor® m s made. As the sorb m the reduction of thfOlium (III) to thallium (I) proceeded, it became necessary to study the oxidation of thallium (I) to thallium (XXX)* Thallium (III) aside is the most easily prepared (ttt) compound and potassium ferrieyanlde is the only alkaline oxidant proposed for the quantitative precipitation of thallium (1X1) oxide, Since potassium ferrtcyanide Appeared to have disadvantages as an alkaline oxidant, a study of sodium hypochlorite m m made, A study of the oxidation of thallium (X) by sodium hypochlorite indicated that & standard solution of hypochlorite seuld be used for the volumetric determination of thallium* Direct and indirect volumetric methods for the determination of thallium uer© studied by using a standard solution of sodium hypochlorite. During the volumetric uork it appeared that sodium hypochlorite gave a h o mogeneous precipitation of thallium (XXX) oxide* A comparative study of the gravimetric determination of thallium as thallium (XXX) 2 oxide was made using potassium fezrloyaoiide and sodium hypochlorite solutions as alkaline aaeidieiag agents* 3 Moot of the methods for the determination of thallium require that tli® thallium be jsreeent in solution in on© oxidation state only* for ihi® reason th© prolimiBory oxidation or redaction of thallium io of groat importance* Therefor© the literature on. this ©object 1® reviewed before the volumetric and $r«vlmetrtc method® of deiersdnation are di«cu»»©d* Since the work described in this thesis involves the us© of metal© a® rodaotanta, a brief historical review of metallic reducing agent® 1® included* A# Oxidation of Ttm&lium (I) to Thallium (HI) Since oxidant© utills&ed a® standard solutlcns are discussed in Section 0 at part of the various volumetric determinations, the only oxidants included her® are those “ which cannot be need a® standard soimtione. Brown and McGlynn (ID) treated a hot ammonioal solution of thallium (1) sulfate with potassium persulfate* Upon boiling, the thallium (1H ) oxide coagulates end the excess m m m ia i® driven off* Challenger and Masters (16) oxidised thallium (1) to thallium (111) with oaono*. the m m m ® m o m . m m removed by passing air though the solution* B* Reduction of I'halllum (III) t© Thallium (I) ' Sulfur dioxide 1© customarily m od as the reducing agent for the quantitative reduction of thallium (III) to thallium (I)* (19*30)* k The advantage of sulfur dioxide is that no metal lone are introduced that mould Interfere in the determination of thallium (I)* The major disadvantage la the difficulty of rearing the excess sulfur dioxide. 11 least one hour of boiling ie necessary to metm& excess sulfur dioxide* ftresker (62) treated an acidified solution of thallium (HI) with potassium iodide and obtained (x) iodide- iodine* Berry* (S06) need hylroxyXamine ©nifata, iron. (H) sulfate, sodium arsenit© end metallic copper for the reduction of thallium (HI) to thallium (I)* !$7dr©xylainan© sulfate gives quantitative reduction of thallium (XXI) in either acidic or basic solution* tigD* * * n # * ih ^o ♦ Bottom (i) The reduction proceeds more rapidly in alkaline solution hut traces of nitrite sere found* Iron (11) sulfate mHX quantitatively reduce upon boiling a hot acidic solution of thallium (HI) to thallium (X), The kinetics of the reduction of thallium (III) by iron (XX) have been studied fey Johnson (3W sad by Forobheimsr and Eppl© (21*). Berry (6) treated thallium (XXX) oxide with an excess of standard sodium arsentie and found couplets reduction of thallium (XXX) to thallium (I) * Thallium (XXI) in boiling solution m » found to be quantitatively reduced to thallium (X) by the addition of copper metal (5). $ Zlntl and Rienacker (73) report the rapid quantitative reduction of thallium (HI) to thallium (I) with titaniua (HI) chloride in hot acetate solution. Brown and Hc&Lym (10) found that ©low addition of hydrogen peroxide to an acid eolation of thallium (HI) gave quantitative redaction of thallium (HI) to thallium (I). tmtmni (6h) found that on the addition of potassium thiocyanate thallium (III) chloride Is reduced to thallium (X) thiocyaimte according to Equation 2« 3Eiclm o M * m & ® m y m m * m e 1 a HCH * $fci * H#0* Ration (2) bhen thallium (HI) chloride is added to an e&oese of potassium thio~ eyunate, the results are in closer agreement with elation 2* 0# folumetrio Hethods for Thallium Holloas and Spencer (31) treated a thallium cample ■with chlorine gas until thallium (1) chloride dissolved, The solution was acidified and potassium iodide wa© added.# the iodine liberated by the reduction of thallium (IH)f mas titrated with standard sodium thiosulfate using the iodine color in chloroform as the indicator. They report excellent precision and accuracy# Bill and Peterson (SO) treated two to five milligram thallium samples with a bromine reagent mid boiled the solution until only a faint bromine color remained# After cooling, the excess bromine was destroyed by the addition of a phenol solution# Potassium iodide was 6 added and the liberated iodine was titrated ulth standard thiosulfate using a special starch as indicator* Oood results were reported for ism to live milligrams ot thallium* larger concentrations o£ thallium aero low results* The addition of sufficient potassium iodide to precipitate thallium (1) iodide also gave low results* Bresamafely iodine is adsorbed or coprecipitated by the thallium (1) iodide* Barry (6) .treated a thallium (HI) solution with an excess of standard sodium arseuite* The unreacted sodium arsenit® m s titrated with sodium hypochlorite using thallium (I) os the indicator* In alkaline solution# the first excess hypochlorite oxidises thallium (I) to thallium (XU) oxide* The results for thallium were approadLm&bely three per cent lorn* It appears that these low results were due to the slow reaction between hypochlorite and thallium (X)* Berry dstarmi^a thallium fc>y reoucing a thallium (Hi; solution with an m c e m of standard Iron (XI) sulfate solution* After quantlta^ tive reduction of the thallium (XXI) the excess iron (IX) m s titrated with standard potassium dichrornate. Xteil and Blenaeker (73) titrated a hot acetate solution of thallium (XXX) with a standard titanium (III) chloride solution* The precipitation of titanium dioxide m s prevented by the addition of ammonium fluoride* Hydrochloric acid m s found to inhibit the reduction of thallium (XXX) by titanium (III)* Marshall (Ul) recommends the us® of Sodium broaaate for the indirect volumetric determination of thallium (X). The method involves the addition of m excess of standard sodium bronate solution to a thallium 7 sample containing dilute hydrochloric acid and a small crystal of sodium bromide. The excess bromine m s distilled over and treated Tilth potassium iodide. The liberated iodine m s titrated with sodium thiosulfate. Excellent precision and an accuracy of one part per thousand is reported. This method is slow because of the required distillation, Zintl and Rienacker (73) propose a direct titration of thallium (X) in five to eight per cent hydrochloric acid with standard potassium bromate# The end point is detected potentiometrically or by the disappearance of methyl orange indicator at $0 to 60°C, Excellent precision and accuracy are reported# The bromate oxidation procedure is perhaps the best volumetric method for the determination of thallium (I), Bienaeker and Knauel (I46) have adapted the bromate method to the micro titration of thallium for toxicology# Hawley (2?) proposed a permanganate titration of thallium (I) in 6 per cent hydrochloric acid. The method is of little use* since permanganate reacts with the hydrochloric acid* Beale and co-workers (2) found that the chloride ion is necessary for the permanganate titration of thallium (I) and that thallium (X) is air oxidised in 0,8 normal hydrochloric acid, in alternate procedure is described for th© determination of 6 to 100 milligrams of thallium# Sodium fluoride in hydrochloric acid is used to complex Mh (III) as the fluoride. This method is an improvement over Hawley* s method but Is inferior to the bromate method, Hillard and Young (70) propose the use of cerium (I?) sulfate for the volumetric oxidation of thallium (I) in hydrochloric acid. 8 This oxidation will not take place in the absence of hydrochloric acid. Elevated temperature Is necessary for a rapid reaction. For usual end point detection, the solution must be between 85 and 100°G. This method is reported to yield good results but is not attractive due to the difficulty of detecting the equivalence point. Tomicek and Joaok (66) report the oxidation of thallium (I) to thallium (XXI) by sodium hypobromita in 1.5 to 2,0 normal sodium hydroxide. They proposed the use of thallium (X) carbonate for th© Standardization of hypobromite solutions. Excellent results were obtained* Tomicek and Filipovlc (65) state that calcium chlorohypochlorlte is less suitable than hypobromite for the alkaline oxidation of thallium (X), They reported low results which oould not be improved. Berry (8) states that chloramine^T will quantitatively oxidize thallium (X) to thallium (XXX) in a dilate hydrochloric acid solution containing bromide ion. Methyl orange is used as the indicator. Swift and Garner (63) determined thallium (I) in three to five normal hydrochloric acid solution by titration with a standard iodate solution using the iodine monochloride end point, Excellent results are reported. Smith and Wilcox (5U) titrated a 1*0 per cent hydrochloric acid Solution of thallium (I) with a standard iodate solution using 0.05 ml. of dilute amaranth solution as Indicator. The end point was detected by the destruction of the amaranth color by a slight excess of iodate. Excellent results are reported. 9 Singh and Singh (f?X) state that thallium (1) la tire normal hydroOhiorid m i d a m bo titrated with a standard potassium chlorate solution using Iodine monoehlorlde as catalyst* Mehrota (U2) states that a standard iodide solution can be titrated with a thallium (I) solution using broB^hanolblue m m adsorption indicator* Whan the titration Is kept oat of bright light, the first excess thallium (l) causes a color change from violet to bright green* Good precision and accuracy are reported* this method has the dis­ advantage that Ihe unknown 10 need as the tibrant • Browning and Faimer (13) estimated thallium by adding a measured volume of standard ferricyanid© to an alkaline solution of thallium (I)* the thallium (III) oxide was removed by filtration, and the filtrate was acidified*, the ferrocyaaide was titrated with standard potassium, perjaaaganate, Berry (5) found the end point to be poor in the- ferrleyanidepermanganate titration* B* Gravimetric Determinations of thallium One of the most popular gravimetric methods for the determination of thallium is based on the precipitation of thallium (1) from a dilute aimaoniacal solution by the addition of potassium ehromate (30)* The precipitate Is dense and easily handled* However, thallium (I) chroiaate Is soluble in the precipitating solution to the extent of six milli­ grams per liter (U3)# This solubility loss would give a negative error of considerable magnitude with samples of low thallium content* 10 Maoh and Lepper (UO) treated a solution of thallium (I) with potassium hydroxide and potassium ferricyanide. The ferricyanlde ion oxidises the thallium (1) to thallium (HI) which precipitates as thallium (III) oxide (TljgOg) in alkaline solution* Oka (hU) reports the £ solubility of thallium (HI) oxide to be 5*93 x ICT milligrams per liter at 25°C., while Sidgwick (U8) reports 2.51 x ICf*0 milligrams per liter at 25°C. The solubility of thallium (III) in alkaline solution is reported to be dependent on the method of precipitation (6,12)* Th© black modification formed in strong alkali is less soluble than th© brown modification* Duncan (21) states that on heating, thallium (HI) oxide begin® to lose oxygen at 100°C* Duval (22) reports that the oxide formed in alkaline solution may be used as a weighing form, if dried between 100 and 230°C• in th© absence of carbon dioxide* Werther (68) and Long (39) precipitated thallium (I) iodide from a hot dilute acetic acid solution of thallium (I) by the addition of potassium iodide* The sample solution must be free of substances such as silver or copper that precipitate m iodides or substances such as titanium that hydrolyase in dilute acetic add* All the thallium must be in the plus one oxidation state prior to precipitation* This is achieved by reduction with sulfur dioxide and boiling to remove th© excess* The solubility of thallium (I) iodide in water is reported to A be 0.08H7 grams per liter at 26 C* (35)* Th© solubility is decreased in solutions containing a little potassium iodide, acetic acid, or alcohol* This method is not recommended due to th© appreciable solu­ bility of the precipitate. n Cushman (30) used chXorcplaiinic acid for th® precipitation of thallium (1) from dilute acid solution, Thallium (1) chloroplatinate in th® least soluble of th® chLoroplatinates* Xhaval (22) recommends drying th® precipitate between 65 and X55°C * , K&wley (2&,2$) reported the use of sodium tetrasulfoataaaate is a precipitating reagent for th® determination of thallium (I) in dilute acid# Th© prodpitat® has th® formula T1*£«S** Th® excess tin (17) aolfid® 1®. removed a ® the soluble tbiostanmt® ion by adding a .sodium sulfide solution and boiling* Th© precipitate Is- dried at 15Q°C* BovaX (22) states that the precipitate is m % a suitable weighing form*; Smith 05} proposed tetraphenyl arsoniuachloride for the quantita­ tive precipitation of thallium (III) as tstsgpftasp&ereMtatti ehloro-* thallab© * Th® precipitation is carried out in 0*2 to 0*5 normal hydrochloric add* An accuracy of an® part per thousand is reported* Smith states that potassium ehromaie Is the best reagent for th® gravimetric determination of thalllumf and in spit® of the fact that it' tends to .$$?* lot results due to th® solubility of thallium (I) chrornate* Berg and Fahrenkamp (k) recommend th® us© of thtonalide ( **m®rcapto~ H-naphihylaoctamXd©) under controlled conditions as a specific reagent for the estimation of thallium (I) *■ The reagent is specific for thallium (I) when precipitation Is carried out in an alkaline cyanide solution* th® precipitate is thoroughly washed with water to remove cyanide and then washed with acetone to remove th® excess thionalide* Buval (22) .states that the precipitat® may b© dried between 69 and i£6°G* 12 Browning (H) proponed weighing thallium (I) an the sulfate or acid sulfate after Isolation of the thallium. He states that the acid sulfate may- be dried to constant composition between 220 and 2U0°C. Weighing as the sulfate requires drying in platinum to a dull red heat, Duval (22) states that the sulfate may be dried between 92 and 355°C, E, Traoe Methods A number of methods have been proposed for the determination of email amounts of thallium* Povelka and Morth (U5) determined thallium in concentrations of Q.GOU mg, per si, by measuring the color of the thallium (X) phosphoraolybdat© hydrosol. Lead* bismuth, mercury (IX) and cadmium ions do not interfere, but potassium and ammonium ions must be absent since they form insoluble salts with the phosphomolybdic acid, An accuracy of on® to five per cent Is reported, Shaw (UT) separated thallium (III) chloride by an ether extraction. The thallium (XIX) chloride was treated with potassium iodide and the liberated iodine was extracted in carbon disulfide* The carbon disulfide extracts were compared to standard series* This method is applicable to concentrations of 0.0U to 0,16 milligrams of thallium per ml, of carbon disulfide. Haddock (26) modified Shawfs method by extracting thallium (I) in chloroform with dithizone, conversion of thallium to trivalent state, reduction with potassium iodide, and measuring th® starch iodine color with similarly treated samples, The method is applicable for 0,005 to 13 0«t milligram of thallium in the presence of 0W$ gram ef Oliver, copper, cadmium, antimony, chromium and Iren* $111 and Peterson (&9) measured the fluorescence of microgram quantities ef thallium (I) In 1 to 2 normal hydrochloric acid* A large number of interferences moot he removed prior to measurement* Flaschka ($3) treated eolations containing from 0«025 to 5*0 milligrams of thallium with Solid magnesium m m s complex* the dis­ placed magnesium mas titrated with standard verson© in the presence of erloehroae black as indicator* Buck, Farrington and Swift (lh) determined thallium (I) by eoulometric titration using generated bromine or chlorine* the end point was determined by a rotating platinum electrode having m applied e*m*f. of 200 millivolts* An error of 0*2 per cent is reported for thallium concentrations from 93 to 1900 micrograms* F* Metallic Redactors Metallic redactors are often used for preparative work prior to a volumetric oxidation* Analysis by volumetric oxidation assumes that all of the species being determined are present in the same oxidation state* Preliminary treatment, for example dissolving the sample, may effect quantitative conversion of the species to the desired oxidation state* In most cases, quantitative reduction la nscossasy before the measured reaction is carried out* two requirements are necessary for reducing agents that are to be used prior to volumetric oxidation* 1. The reducing agent employed must be stable in the oxidised form in XU order that it Kill not consume th© standard ©aidant being used* t« fho excess reducing agent mot be removed prior to th© measured reaction, the first condition is easily satisfied by using a reducing agent having only one stable oxidation state in solution, the method to be used for removing the excess reducing agent is dependent on the material being used, Metallic redactors satisfy both of the above conditions, m the column reductor, the removal of excess reducing agent is automatic, the column redactor also offers the advantage of rapid reduction due to the large surface area of the metal* Liquid amalgams are not used extensively as reducing agents due to the difficulty of separating the amalgam from the aqueous phase* Hillebrand, Lundell, Hoffman and Bright (30) describe in detail the preparation and uses of the Jones and silver redactors* Cooke and co-workers (18) describe the preparation of a lead redactor and its use for the redaction of uranium (VI) to uranium (If)* the lead redactor has the advantages that amalgamation Is not necessary and ammonium ions and acetate ions do not interfere. Mien sulfuric acid solutions are used, m adherent film of lead sulfate forms on the lead, which rapidly decreases the reducing action of the redactor* the formation ©f a lead sulfate film can be prevented by hydrochloric acid, if the hydrochloric acid concentration is 2,3 normal or greater* Treadwell and co-workers (67) describe the preparation and uses of a cadmium reductor* The cadmium redactor can be used in hydrochloric ©r sulfuric acid and has been recommended for the following reductions* 15 Fe (III) to Fe(II), Ti (IV) to Ti (III), Mo (VI) to Mo (III), V (V) to V (II) and U (VI) to U (IV) and U (HI). Brlnn (9) recommend. the use of a cadmium rod for the reduction of Fe (III) to Fe (II) in either hydrochloric or sulfuric acid. Yoahimura (72) proposes the use of a bismuth column for the re­ duction of Fe (III) to Fe (II), Ti (IV) to Ti (III) and U (VI) to U (IV). Metallic nickel in a carbon dioxide atmosphere at room temperature can be used as a reducing agent for Cu (H), Fe (III), Sn (IV), Ti (IV), U (VI), W (VI), V (V) and Mo (IV) (71). Boiling solutions of the above ions in a carbon dioxide atmosphere can be reduced by metallic antimony (71)* Smith and Wilcox (53) recommend th© us© of Woods metal for the reduction of Fe (HI) to Fe (II) in dilute hydrochloric or sulfuric acid. Woods metal is an alloy of 50 per cent bismuth, 25 per cent lead, 12.5 per cent tin and 12.5 per cent cadmium. Th© alloy melts at 65*5°C. and can conveniently be removed by letting it cool and separating the solid. A series of papers by Someya (56,57,58,59,60,61) describe the preparations and uses of zinc, bismuth, cadmium, lead and tin amalgams. Smith and Kurts (52 recommend carrying out amalgam reductions in an Erlenmeyer flask. After reduction, they add 50 ml* of carbon tetra­ chloride which forms a layer separating the amalgam from th© aqueous phase. Titrations using indicators can be performed on the aqueous phase by gentle swirling so that th© amalgam does not contact the aqueous phase. Hop© and co-workers (32) describe a glass reduction cell useful for amalgam reduction in an atmosphere of carbon dioxide. KXFSHIKBNTAL 16 1 Standard Solutions All reagents vised in this work were, unless otherwise stated, analytical reagent grade* All plpets and berets sere calibrated and corrections sere applied where necessary. All sellings sere made with calibrated weights. Sodium arsenit©, 0,1000 normal, was prepared from Baker and Adamson Primary Standard Analytical Reagent arsenious omlde, which had been dried at H 0°0, for two hours, Approximately 16 grams of sodium hydroxide pellets and 60 ml, of water were added to 9•8910 grams of the dried reagent. After tlje mixture dissolved, it was diluted with water to 300 ml,, neutralized with dilute sulfuric acid, treated with 6 grams of sodium bicarbonate, and diluted to two liters. Potassium brornate, 0,1000 normal, was prepared from Mallinckrodt Analytical Reagent (trade potassium bromate which had been dried at 110°Q. for two hours, the Mallinckrodt assay was 92.8 per cent. Two liter batches were prepared by dissolving 5,5792 grams of the dried reagent in distilled water and diluting to two liters , Sodium hypochlorite solutions were prepared by diluting various quantities of commercial bleaches. The preparation of two liter solutions of 0,1 normal sodium hypochlorite required 130 ml, of Clorox, 130 ml* ©f Roman Cleanser or 190 ml. of Fleecy White Bleach. These diluted solutions were stored in amber bottles and kept out of direct sunlight. The bottles were ©quipped with siphons and soda lime traps. 17 Sodium hypochlorite, 0*1 normal, pH of 12, was prepared by dl1#> lag 130 ml# of commercial Clorox to two liters end adding sodium hydroxide pellets until the required pH was registered on a Beckman H2 line operated pH meter# The solution was stored in an amber bottle and kept oat of direct sunlight. Sodium hypochlorite, 0.1 normal, and 0*6 normal in hydroxide was prepared by diluting 130 ml* of commercial Clorox to two liters and adding grams of sodium bydroxids pellets* The solution was stored in m amiber bottle and kept out of direct sunli^rfc* A gallium solution, G*Gl£8 molar, was prepared by dissolving 0*1102 grams of fisher Scientific gallium metal in a mixture of 2 ml* of concentrated sulfuric acid and 1 ml* of concentrated perchloric acid and diluting to 100 ml* An iron (11) chloride solution, containing 0*171* milligrams of iron (II) per milliliter, was prepared by dissolving 0*08?0 grams of Mallinekrodt standard iron wire in 10 ml* of 6 normal hydrochloric acid and diluting to 100 ml* Bordeaux. A 0*2 per cent aqueous solution was prepared from Bordeaux, British Color Index 88, 0* Frederick Smith Chemical Company. pjphenylaraine sodium sulfonate, 0*0! molar was prepared (6p) by dissolving 0*32 grams of diphenylaain© barium sulfonate in 100 ml. of water and adding 0*5 grains of sodium sulfate. After standing over night, the clear solution was decanted from the precipitated barium sulfate* 18 Sodium hypochlorite, 0,1 norma1$ was standardised by the fallen* ing procedure which le essentially that of Koltfaoff and Stenger (36)* To tk*9k ml. of the standard sodium araenite solution in a 125 ml. Brlenmeyer flask sere added 1*0 gram of potassium bromide, 1,0 gram of sodium bicarbonate and one drop of Bordeaux indicator. The sodium arsenlte solution urns titrated with the hypochlorite solution until the indicator faded, tee more drop of indicator m s added and the titration continued until a fraction of a drop caused the indicator color to flash from pink to colorless or pale yellow. An Indicator blank of 0,01 ail, of 0,1 normal sodium hypochlorite was subtracted from the volume of hypochlorite used* II Stability Studies of Sodium Efrpochlorite Solutions Aqueous hypochlorite solutions are known to be strong oxidising agents, but reasonably stable solutions have been prepared by many investigators* Jellinek and Krtsbeff (33) prepared ©odium hypochlorite by passing chlorine Into a 0*1 normal sodium hydroxide solution. The resulting solution was stored in a clear glass bottle and in 1? days the normality changed from 0,1352 to 0,1330, The authors infer that sunlight accelerates the decomposition of hypochlorites* Chapin (1?) studied the deconposition of sodium hypochlorite a© a function of pH and found that a pH of 13*1 gave maximum stability* Buffer mixture© containing acetate, borate, carbonate and phosphate ions were found to accelerate the decomposition of hypochlorite solutions* 19 Kolthoff and Stenger (36) used H,T*H., calcium hypochlorite manu­ factured by M&tMeaon Alkali Works, for the preparation of hypochlorite solutions* these solutions were adjusted to a pH of 11 to 12 and stored in glass bottles painted black to protect the solutions from light* The solutions were gull© stablef shoeing normality changes from 0*101*7 to 0*1035 Aiisix months* 0*0895 to 0.0801 in six months and 0*1262 to 0*1230 in 16 months. Calcium hypochlorite solutions have the disadvantage that 01* standing a precipitate of calcium carbonate settles out* Goldstone and Jacobs (25) used Clorox, a commercial bleach, as a source of hypochlorite. They adjusted the diluted Olorox solution to a pH of 12*5 and stored these solutions in dark bottles out of direct sunlight, Their solutions shewed normality changes from 0.005Q0 to 0,001*98 in 56 days and 0,00557 to 0,0055k in 175 days. A number of variables such as pH* foreign ions and exposure to light Imre been shown to affect the stability of hypochlorite solutions. Calcium hypochlorite solutions hare been reported to be more stable than sodium hypochlorite solutions (36) • Most of the stability studies were made on sodium hypochlorite solutions which were prepared fey passing chlorine gas into sodium hydroxide solutions* Goldstone and Jacobs (25) used commercial Olorox while Belcher (3) used B.D.H. sodium hypochlorite for the preparation of standard hypochlorite solutions* Carlyon (15) used Clorox as a source of hypochlorite and found that 0*1 normal solu­ tions with a pH of ten were reasonably stable, Goldstone and Jacobs 20 were the ©aly Kb# used commercial sodium hypochlorite far Stability stadias, lad their solutions rare quite dilute* la view of the conflicting literature ©a the effect of pH and the lack of information m the eternity of various commercial bleaches the following stability studies sere designed* Sodium hjpo^lerite solutions prepared from various cesaanrolal bleeohes sere stored la saber bottles, which had been thoroughly rinsed with m dilute solution of sodium hypochlorite* These solutions were periodically standardised by titration against 0*1000 normal sodium arsenit©* In triplicate standardizations of a given hypochlorite solu­ tion, the normalities obtained by the first standardization mere uniformly loir* This mas attributed to ineojnplete conditioning of the buret surface* In order to obtain a constant mentality, the buret was filled with hypochlorite solution and allowed to stand 20 minutes, drained and refilled before titrations mere performed* The results in Table X are averages of duplicate standardisations which agreed within two parts per thousand* TABSM I m 0.1 NORMALSOBXSIMHXPOCHLQHITISGLBTB3NS mwmw FROMFAEIO0SCOMWtOm BLEACHES 3T ABHITX Clorox ***1 (f u 9 18 19 22 53 78 0.1081* ** 0,1077 0.1073 0.1081 0.1030 0,1078 0.1077 •» 0.1073 mm 0,1065 0.1070 0.1069 0,1067 0.1067 0.1117 #**» 0*1109 0*1112 0*1113 o.noh 0*1105 oinou 21 the results from Table I indicate that sodium hypochlorite solu­ tions prepared from various commercial bleaches have similar stabili­ ties* The effect of pH on the stability of sodium hypochlorite solutions was determined by* periodic standardisation of 0.1 normal Ghlorox solu­ tions adjusted to varying alkalinity* The results in Table II are averages of duplicate determinations which agreed within two parts per thousand. TABLE II EFFECT OF pH OH STABILITY OF 0.1 NORMAL CLORGX SOLUTIONS Time in Bays 0 2 8 !h 15 28 b3 69 105 Normality of Hypochlorite Solutions O.63&J "i?H » 12 pH ** 10 WaOH 0.1016 0,1015 0.1015 0.1012 *««» 0*1010 0.0999 0.0998 0.0997 0.1GL? 0.101*1* O.lOlih 0.101*0 0.101*2 * *i*> a w ***** 0.101)1 0.1039 0*103h 0.1038 0.102? - - 0.1035 0.1035 0.1021 The solutions studied In Table IX were stored in amber glass bottles which were not rinsed with hypochlorite preliminary* to use* This lack of rinsing may account for the decreased stabilities of the solutions in Table H compared to the more stable solutions In Table I. A change of hydroxide concentration from 0*0001 to 0.61* normal appears 22 to have little effect on the stability of 0*1 normal sodium hypochlorite solutions• A sodium hypochlorite solution with a pH of 12, after being stored in a translucent polyethylene bottle for 28 days, showed a normality change from 0.101*2 to 0*0977* this was a larger normality change than noted for the solutions stored in amber glass bottles* It appears that translucent polyethylene is unsuitable for the storage of hypochlorite solutions* A hypochlorite solution, which was stored in an amber bottle previous­ ly used for hypochlorite storage, had a normality decrease from 0,1011* to 0*1005 in 155 days. It appears that conditioning of a container aids in the stability of sodium hypochlorite solutions. The data in Table I indicate that 0.1 normal solutions of sodium hypochlorite, prepared from various commercial bleaches, have nearly equal stability. The data in Table II indicate that hydroxide concentrations from 0.0001 to 0.61* normal have a negligible effect on the stability of 0.1 normal hypochlorite solutions. Three successive solutions of 0.1 normal hypochlorite were stored in an amber bottle. It was noted that the second and third solutions were more stable than the first. This increased stability may be due to conditioning of the glass surface* It was found that for accurate titrations with hypochlorite, the buret should be conditioned with the hypochlorite solution for 15 to 30 minutes before use. When the buret Is not conditioned, the volumes of hypochlorite used in titrations are found to be too large. 23 Several jrecautions are necessary when preparing stable 0.1 normal solutions of sodium hypochlorite. A 0.1 normal solution is easilyprepared by diluting 130 ml* of commercial Olorox (5.25 per cent sodium hypochlorite) to two liters. The solution should be stored in an amber glass bottle which has been cleaned and thoroughly rinsed with 0.1 to 0,2 normal hypochlorite solution. The prepared solution should stand over night before being standardised against a standard arsenite solu­ tion by the method of Koltboff and Stenger (36)» H I The Use of Metallic Redactors for the Reduction of Thallium (HI) to Thallium (I) Most of th© method® for the determination of thallium require a preliminary reduction of thallium (HI) to thallium (I), and sulfur dioxide is commonly used as the reducing agent. The disadvantages of sulfur dioxide were discussed in section B, Copper metal is the only metallic reducing agent mentioned in th© literature for the reduction of thallium (III). In view of the advantages of metallic redactors in analysis, it seemed desirable to investigate their use for the reduction of thallium (III) to thallium (I), In order to study methods for the reduction and determination of thallium it was necessary to prepare a stable standard solution of a thallium compound. Fisher Sc^Ienbifio Company C#P. thaHi^m^ (I) xii^triat^e was used as a thallium source, since primary standard thallium salts are not commercially available. Approximately 75 grams of Fisher Scientific C.P. thallium (I) nitrate was recrystallised twice from water, air dried and finally 2k oven dried at 110OC* for tvo hours* Speotrographie analysis of the recrystallized salt shotted lead to he absent* A thallium (X) nitrate solution mas prepared hr dissolving 6*6826 greats of the dry reagent In 160 ml* of distilled enter and dilating to $00 ml, Might calibration of this volumetric flask shotted the true volume to be k99*92 ml* Assuming the thallium (X) nitrate to be pore* the calculated normality of this Solution m » 0*10036. As a check m the purity of the thallium (X) nitrate the 0,10036 normal solution use analysed in triplicate for thallium (I) by th® chromate procedure (30) ami the thallium (1X1) oxide procedure (1*0), three 2lw9U ml* aliquots of the thallium solution yielded thallium (I) chromate precipitates of 0.3260, 0*3261* ami 0*3261 grams* After applying the correction for the solubility loss, the average normality is 0.10029* Three 2h»9k ml# aliqfuois of thallium solution gave wights of thallium (XXX) oxide of 0.2863, 0*2861 and 0*2863 grams, giving an average normality of G.IGO'jG* The normalities obtained by analysis m d vdght-volume measurements agree to one part in a thousand. This dose agreement indicates that the minimum purity of the r©crystallized thallium (X) nitrate is 99*9 per cent. A large volume of thallium (X) nitrate solution u&s prepared for the foUotting Studies* Six-hundred ml. of eater containing 36*3981 grams of the dry reagent m s diluted to the mark in a two liter volumetric flask, this eolation use transferred to a dean dry seven liter bottle, 25 To the unrinsed volumetric flask was added 600 ml, of water containing 19 .1*550 grains of the dry reagent* The flask was diluted to volume and Its contents were added to the solution in the seven liter bottle. The calculated normality of this solution is 0*1014. 8. Since the 0,101*8 normality of th© thallium solution was question­ able, the solution was analysed by th© bromate and chromat© procedures* In standardisation by the chromat© method, five 2l*#9U A * aliquots of th© thallium solution yielded thallium (I) chromate precipitates weighing 0.31*05, 0.31*07, 0.31*05, 0.31*21 and 0*31*09 grams* After apply­ ing the correction for th© solubility loss, th© average normality is 0.101*8. Th© volumetric bromate method of Zintl and Reinacker (73) was used to standardise the reference thallium solution. Two 19.97 ml. aliquots required 20.95 and 20*95 ml# of the standard 0.1000 normal potassium bromate solution, giving a normality of 0.101*9* Duplicate 29.97 ml# aliquots required 31*39 and 31.1*7 ml. of the standard bromate solution, giving an average normality of 0*101*9. The equivalence point was detected potentiometrieally by the us© of a pl&tinum-calomel couple and a Fisher Titrimeter. The normality, 0.101*9 obtained by the bromate method agrees well with the calculated normality of 0.101*8. Thallium (III) sulfate, 0*1 normal, was prepared from thallium (I) nitrate in the following manner. Fifty-four grams of th© thallium (I) nitrate was dissolved in 900 ml. of water and the solution madebasic with sodium hydroxide pellets. Th© basic solution was treated with 3f>0 ml* of commercial Olorox and digested on a steam bath. 26 The thallium (HI) oxide precipitate m s washed twice by decantation and then dissolved in 220 nil* of concentrated sulfuric acid* The solu­ tion was heated to fumes of sulfur trioxlde and on cooling, the sides of the beaker were washed down with distilled water. The solution was heated to sulfur trioxide fumes a second time and on cooling was diluted to four liters* The thallium (HI) sulfate solution was analysed for total thallium content by the volumetric bromate method (73)* Two 19*97 ml. aliquots were reduced with sulfur dioxide and boiled for one hour to expell the excess* These aliquots required 20*88 and 20.84 ml. of 0*1000 normal potassium bromate. Three blanks were run in order to determine the amount of sulfur dioxide remaining after one hour of boiling* The blanks required 0*04, 0*0? and 0.03 ml. of 0*1000 normal potassium bromate, giving an average blank of 0,05 ml* After subtracting the 0.03 ml. blank, these determinations give an average normality of 0,1043 for total thallium in the thallium (111) sulfate solution* The thallium (X) concentration in the thallium (XIX) sulfate solu­ tion was determined by titrating two 19*97 ml. aliquots with 0*1000 normal potassium bromate * These titrations required 0*74 and 0.76 ml* of standard bromate solution, giving a normality of 0*0038 for thallium (I), Since the total thallium concentration is 0*1043 normal and the thallium (I) concentration is 0.0038 normal, the thallium (III) normality is 0.1005. 27 4 * Cadmium Redactor 4 ©adnfosm redactor m s prepared i& the following manner* Saadi cadmium filing were obtained by fHimg a. cadmium rod (Fisher Scientific Company) with a eoarea tile* The filings, approuiimtely 30 mesh in eta©# were washed in on© normal hydrochloric acid and in one normal sulfuric acid* The washed tiling® war© placed in a Fyrex glasw redactor fitted with a glass wool plug and equipped with a glass stopcock. These rednotera are commonly need a© silver redactor© and can be par* chased from th© 0* F* Smith Chemical 0©wpa*j0r* Th# 20 cm* cadmium column was washed by passing one normal sulfuric acid through the redactor* When not in mo the redactor was filled with one normal sulfuric acid* Measured Quantities of th© 0*1®£*J normal thallium (XXI) sulfate Halation were treated rearing ©f one normal sulfuric acid and diluted* Samples containing 212.0 adlXigrams of thallium were diluted to 10® ml* and the smaller samples were diluted to $Q ml* thee© add solutions were passed through the cadmium redactor at a measured rate*. The column m i washed with three 5® mi* portions of dilute sulfuric acid* Sine© the volumetric bromate method requires the solution to be five to eightper cent in hydrochloric acid* the sola* tions were treated with 3® ml* of slat normal hydrochloric or with 12 %?mm of potassium ohloiido* The thallium (I) solution was titrated with 0*1000 normal potassium bromate and the equivalence point was detected by the use of a Fisher Titrimeter with platinum and calomel electrodes* Five blank® were rum on the cadmium redactor and 0*06, 0#®S# Q.Qb, 0*06 and ®#05 aCL* of Q.1Q0O normal potassium bromate were 28 ©oneumed, An average blank ©f 0,0$ ml* was subtracted from the volume of 0*1000 normal potassium bromate meed* the results ©btaiiwd using the cadmium redactor ere tabulated in Table in* A silver redactor was prepared in the wane maimer as the ndtdii redactor % replacing the cadmium metal with granular silver (a* F, Smith Ohemieel Company) * The 16 m * silver column m e washed by passing one normal aulfori© m i d through the reduotor* When net in nee the redactor m e filled with one normal sulfuric acid* Measured quantities of th© 0,101*3 normal thallium (111) sulfate solution were treated with varying amounts of o m normal sulfuric acid and diluted* Samples containing 212*8 milligram ©f thallium sere diluted to 100 ml* and the smaller samples sere diluted to $0 ml* These acid solutions sere passed through the silver column at a moacured rate* The column m e sashed with three 0 ml* portions of dilute sulfuric acid. The reduced solutions were treated with 30 ml, of six normal hydrochloric acid or with IS grams' of potassium chloride* The thallium (1) was titrated with 0,1000 normal potassium bromate. The equivalence point was detected by using a Fisher Titrimeter equipped with platinum and calomel electrodes* Five blanks were run on the silver redactor giving values of 0,02, 0,03* Q*03# 0,02 and 0.0U b£U of 0*1000 normal potassium bromate* An average blank of 0*03 ml* of 0,1000 normal potassium bromate was subtracted from the volumes of bromate used* When hydrochloric acid is added silver chloride pre* eipltates, but apparently thallium chloride is not coprecipitated since 29 TABLE TTT RBOTQTI08 OP O U f f l (XXX) fO THAIXIDH (I) TOXHS A CADMIUM RE530CTQH Stop!* Acidity of Acidity of Hwafaw Dilutod Washings Solutions .l( (m l./w in. ..,,, X 2 $ k S. 6 1 a 9 10 XX 12 13 XI* IS 16 X? 18 19 m n m 1*0 Owl 3u® 1+0 1*0 1.0 0*2 1*0 1*0 1.0 0.8 X*6 2.0 G+2U X*f> 0.1* 0o i t 1.0 0.6 1.0 1.0 1.0 Plow Rats w m » ™ « «•* t w i n a * Error "' ^ g K B ' " FoiuadT” 1.0 w Q.01» 0. 01U 0. 01K 0.018 1.0 0.01 0*01 0,01 0.01 1.0 1*0 1.0 1.0 1*0 0,01 0.01 1.0 1,0 1*0 0,01 0.01 30-50 30-50 25-35 25*35 20-30 30-50 30-50 25-35 20*30 20-30 1* 0-50 1) 0-50 lio—5o 1* 0-50 1* 0-50 20 20-30 25 15-20 25 1*3 20-25 (ms.) 32.0 32.0 32.0 32.0 32.0 53.1 53.1 53.1 53,1 53.1 105, 1* 106. 1* 106.1* 106, 1* 106. 1* 106.5 XEM$*5 212.8 212.8 212.8 212.8 212.8 32. 1* 31.7 31,7 31.9 38.0 53. 1* 53.2 52.9 52.9 52.5 106. 3* 106, 6* 106, 0* 106. 3* 106. 3* 106. i t 106,3 213. 3* 212. 8* 212.6 212.2 212.7 *X2 tfiwMw* of KSX sddsd SaagOoS X-X7 dilutod to SO ml., 18-22 diluted to 100 ml. *0„X *0*3 -0*3 *0*X 0*0 0*0 #0*X *0*2 *0*2 • * 0*6 *0 *X #0*2 «*0*li ~Q*1 «*0*X *0 .X 6* 0*2 #o*5 0*0 *•0*2 •0*6 **G*X 30 results for thallium tend to b© high* the results are given in table 17. t m s i7 Ew m s m t Of THALLIUM ( m ) f© M 1M A m ttm REDACTOR (I) mrnm le or 1 a 3 & $ 6 7 8 9 10 11 12 13 Hi IS 16 17 13 19 Acidity of Acidity Flow Bate Minted of Wash Solution Solution 1*0 1*0 1*0 1*0 1*0 1*0 1*0 1*0 0*ii 2*0 Ovk 1*6 1*0 1*0 1*0 1*0 1*0 1*0 1.0 1*0 0.61 0.61 0.01 1.0 0.01 0.01 0.01 1.0 1.0 1,0 0.01 0.01 0.01 1,0 0.01 0.01 0.01 0.01 It grams of KOI added* 20-30 25 *5 85 20-30 25 25 25 1*0 30-1*0 30-1*0 30-1*0 25 25 10 17 26 25 20 Error 32.0 32.0 32.0 32.0 53.1 53.1 53.1 .53.1 106.ij 106.U 106.1* 106.1* 106.5 106.5 212.6 212.8 212.8 212.8 212.8 32.0* 32.0 31.8 32.0 53.8* 53.0 53.1 53.0 306.6* 106.7* 107.0* 107.3* 106.6 106.U 212,8*? 213.1* 213.3 213.2 212,6 ©*© 0*0 0*0 ♦0.7 —0 *1 0*0 *0.1 ♦o.a ♦0*3 ♦o.s ♦0*9 ♦0*1 -0*1 0*0 ♦0*6 ♦o #S *0.1i 0*0 31 C. Bismuth Reductor A bismuth reductor was prepared by th® same procedure used for the cadmium reductor, but the cadmium was replaced with 99*98 per cent lump bismuth (Fisher Scientific Company), The large lumps of bismuth were removed leading smaller particles of approximately 30-100 mesh. The 20 cm. bismuth columa was washed by passing one noxml sulfuric acid through the redactor* When not in use the reductor was filled with on© normal sulfuric acid. Measured quantities of the 0*101*3 normal thallium (IH) sulfate solution were treated with varying amounts of one normal sulfuric acid and diluted. Samples containing 212.8 milligrams of thallium were diluted to 100 ml. and the smaller samples were diluted to 50 ml. These acid solutions were passed through the bismuth column at a rate of 38 ml. per minute and the column was washed with three SO ml. portions of 0.01 normal sulfuric acid. The solutions containing the reduced thallium were treated with 30 ml* of six normal hydrochloric acid and titrated with Q.10QQ normal potassium bromate. Three blanks were run on the bismuth reductor and each was found to consume 0.G2 ml. of 0.1000 normal potassium bromate. A reductor blank of 0.02 ml. of 0.1OO0 normal potassium bromate was subtracted from th© volumes of bromate used. The data on th© bismuth reductor are tabulated in fable V. 32 TABLE V R E DU CT I ON O F T H AL L IU M (III) T O T H AL LI U M (I) U S I N G A B I S M U T H REDUCTOR Sample Number 1 2 3 k 5 6 7 8 9 10 11 12 13 Hi 15 16 Acidity of Solution (N) 1.0 1.0 1*0 1*0 1*0 0*2 1,0 1.0 1,0 1.2 1,2 1.2 1.0 1*3 1*3 1.3 Milligrams of Thallium Taken 1 r' * jFound Error 32.0 32.0 32*0 32*0 53*1 53.1 53.1 53.1 106.5 106.5 106.5 106.5 212.8 212,8 212.8 212.8 •0.1 *0.1 0,0 -0,1 0.0 —0 *3 +0*1 0.0 ■*o.U -0.1 0*0 +0*1 0*0 +0.5 +0*3 +o*U 31.9 32.1 32.0 31.9 53.1 52.8 53.2 53.1 106.1 106.1* 106.5 106.6 212.8 213.3 213.1 213.2 Samples 1-12 diluted to SO ml., 13-16 diluted to 100 ml* P* Nickel Reductor A nickel reductor was prepared from 99 per cent 18 gauge nickel wire (Driver Harris Co., Harrison, New Jersey)* Shears were used to cut the wire into one to two millimeter lengths in order to increase the surface area. The reductor was prepared in the same manner as the cadmium reductor* Th© reductor was washed by passing one normal sulfuric acid through the column* Wien not in use th© reductor was filled with one normal sulfuric acid. 33 m m & i sd A HIGKSL Hismcm 1 8 3 li 5 6 SI 6 83 13 13 19 32»© 53.1 53.1 W6.S 212.8 212.6 31.5 •0.5 52.0 • 1.1 53.6 106.1 *0.5 213.1* 213.!** *S«nplm 1-U diluted to 50 *!♦» 5*6 dilutad to 100 ml -0.U ♦0.3 * 0.6 3U E* L e a d R ed uctor A l e a d r eductor m s pre p ar ed b y the s ame procedure u s e d for p r e ­ p a r i n g t h e cad mi u m reductor# S cientific Company) m s T h i r t y m e s h granular l e ad (Fisher washe d w i t h sisc n or m al hydrochloric a ci d be f o r e b e i n g p l a c e d i n t h e reductor* The 18 cm* l e a d column m s p a s s i n g on e n o r m a l sulfuric a ci d through the reductor. m s washed b y T h e reductor f il l ed w i t h one n o r m a l sulfuric a c i d m e n n o t i n use. M e a s u r e d quantities of t h e 0.10U3 n o r ma l tha ll i um ( I U ) sulfate s o l ut i on were t r e a t e d w i t h dilute sulfuric acid and diluted to k n o w n v o lu me * The 212*8 mil l ig r am sample m s smaller samples w e r e diluted to 50 ml. d iluted to 100 ml* and the T h e diluted solutions were p a s s e d t hr o u g h the le ad reductor at a r a te of approximately 25 ml* p e r minute. T h e reductor m s w a sh e d w i th th ree 5 0 ml* por ti o ns of one n o r m a l sulfuric a cid a nd the wa s hings were added to the reduced thal l iu m solution* Th e c o mbined solution m s treated w i t h 12 grams o f p o t a s s i u m c hloride and ti trated w i t h 0.1000 normal po t a s s i u m bromate* A Fish e r T i tr i m e t e r equipped w i t h p l a t i n u m and c alomel electrodes was u s e d to detect t h e equivalence point. T h e results obtained u s i n g the lea d reductor are tab ul a te d i n the o r d e r i n which t h e y w e re carried out and a r e list ed i n T a b l e VII* Two 1 0 6 . 9 m i l l i g r a m samples of t hallium (I) nitrate w ere treated w i t h dilute sulfuric acid and diluted to 50 ml* These samples were p a s s e d th r o u g h the l ea d reductor a n d treated i n t he same m a n ne r as th e t ha l l i u m (HI) samples. Tit r at io n w i t h 0*1000 n o r m a l p o ta s s i u m brom at e y ie l d e d 105*7 a n d 106.7 milligrams of thallium. 35 TABLE V II REDUCTION OF THALLIUM (III) TO THALLIUM (I) USING A LEAD REDUCTOR Saaqpl© Number Acidity of Diluted Solution (») .............. 1 2 3 h 5 Milligrams of Thallium Taken " Found Error (Mg.) , . _ T I ............. I n . 0.4 0.4 0.4 0.2 0.4 106.4 106.4 106.4 106.4 212.8 105.3 105.2 100.7 85.3 4.72 —1.1 -1.2 -5.7 -21.1 -208.1 F* Aluminum Reductor Am aluminum reductor 'Has prepared In the same manner as the cadmi.ua reductor by using 30 mesh granular aluminum (J. T* Baker Coi^any). The 18 cm* aluminum column m s mshed by passing 0.01 normal sulfurie acid through the reductor* When not in use the reductor Has filled Hith 0.01 normal sulfuric acid. A h*99 lit* aliquot of the 0.10U3 normal thallium (III) sulfate solu­ tion m s diluted to 50 ml. and passed through th© aluminum reductor at the rate of 12 ml. per minute* The reductor m s Hashed with three 50 ml* portions of 0.01 normal sulfUric acid. The thallium solution and th© Hashing© were treated Hith 30 ml. of six normal hydrochloric acid. Titration of the sample Hith G.1QGG normal potassium bromate required 5.00 ml. The reaction m s slow* If the thallium (HI) m s quantitatively reduced to thallium (1), the calculated volume of 0.1000 normal potassium bromate would be 5.20 ml. 36 to a second iu99 ml* saiqiie of 0*101*3 thallium (XU) solu- 1KiM 000 added $0 ml# of one normal sulfuric acid* flda solution nee p&eaed through the redactor at the rate of XI ml* per minute, hat the rate of flew was erratic dee to the evolution of hydrogen* the thaSMum solution mid the washings were treated with 30 ml* of six normal lydrochlorlc acid and titrated with 0*1000 normal potassium bromate. fko titration required 5.18 ml. of bromate solution* The reaction was Sloe $md detection of the equivalence point mas difficult* A sine reductor was prepared from 30 mesh sine (MalliiMa^rodt Analytical B©agent) by the same procedure used for the cadmium reductor * the sino was washed in one normal sulfuri© acid- before bein-g placed in the reductor. The 16 cm* ainc column m s washed by passing G.G1 normal sulfuric acid threu^a the redactor* When not in use the redactor was filled with 0*01 normal .sulfuric acid* A fm0 WX* sample of the 0 .10^3 normal thaXMwm (1X1) sulfate solu­ tion m s adjusted to m acid concentration of o m normal with sulfuric acid and diluted to XQO ml* After passing the solution through the sine reductor and adding 12 grams of potassium chloride, a titration of the thaniwm (I) required 0*21 ml. of 0*1000 normal potassium bromate* fhs solution was then passed through th© cadmium reductor. The solution required less than 1*00 ml. of 0.1000 normal potassium bromate. A second sample of 9*98 ml* of thallium (XXX) sulfate was adjusted to 0*2 norma1 with sulfuric acid and diluted to 100 ml* After passing 37 t h e s olution t hrough t he zinc redactor a n d ad d i n g 12 grama o f p o ta s si u m c hl or i de a t i t r at i on r eq u i r e d approximately 0.3 ml* o f 0 * 10 0 0 normal p o t a s s i u m b r o m a t e solution. If the thallium (III) solution was q u an t it a ti ve l y reduced to thallium (I), the calculated v o l u m e of 0.1000 n o r m a l p o t a s s i u m b r o m a t e w o u l d b e 10.Ul ml. H* Amalgamated Zinc Reductor A n amalgamated zinc reductor was pr epared in the following manner. O ne - h u n d r e d a n d thirty-five grams of 30 m e s h zinc (Mallinokrodt Analyti­ c a l Reagent) was wash e d for several minutes w i t h one normal hydrochloric acid. Th e w a s he d zinc was treated with 28 ml* of 0 .25 molar m e r c u r y c h l or i de (22) a n d stirred f o r three minutes* The one p e r cent amalgamated zinc w a s plac ed in a reductor column and washed w i th one normal sulfuric acid. The 20 cm. amalgamated zinc reductor was fill ed with one normal sulfuric acid w h e n not i n use. A 9.98 ml. sample of the 0.1Qh3 normal thallium (III) sulfate so l u­ t i on was diluted to 5 0 ml. and t h e n adjusted to one normal w i t h dilute sulfuric acid. After p a ss i ng th© solution t h rough th© amalgamated zinc redu c to r and adding 12 grams of potassium chloride, a titration required 0.09 ml. of 0 . 10 0 0 normal potassium bro m at e solution. If th© t ha ll i um (III) was quantitatively reduced to th a llium (I), the calculated volu m e of 0.1000 normal potassium b ro ma t e w o u l d b e 10.Ul ml. After the f b r o m a t e t i tr ation sulfur dioxide was bubbled through t h e solution a n d the excess wa s removed b y boi li n g the solution for one hour. A t it r ation w i th 0 . 1 00 0 normal p o ta s s i u m bromate required less than 0.10 ml. 38 I* Cadmium Amalgam A cadmium amalgam, three pm? cent cadmium, m m prepared by mixing three grama of o i M i s metal (Fisher Scientific Company), ?*U sail* of Ceneo triple distilled mercury end 15 ml. of six normal sulfuric acid, this mixture was heated several hours on the steam bath and cooled, fh© amalgam m e separated from the undlssolved cadmium by use of a separatory funnel and stored under one normal sulfuric sold, A 10*00 ml* sample of 0*101*3 normal thallium solution m m added to 100 grams of cadmium amalgam and shaken for two minutes in a separatory funnel* the .amalgam use drawn off and sashed teles with 20 ml* portions of erne normal sulfuric acid. The reduced thallium solution and the washings m m combined m & filtered through a Solas crucible* ton grams of potassium chloride was added to the combined solution and titration with 0*1000 normal potassium bromate required less than 2*0 ml* A three per cent lead amalgam m m prepared by mixing three grams of MaXlinckredt Analytical Eeagent granular lead, fmk ml* of Cenco triple distilled mercury and 15 ml* of six normal hydrochloric acid* After heating several hours on the steam bath the amalgam was cooled, Separated from the undissolved lead and stored under one normal hydro­ chloric acid* A 10*00 ml* sample of 0*10^3 normal thallium (III) solution was added to 100 grams of lead amalgam and shaken for tm minutes in a 39 separatory funnel. A dense white precipitate of lead sulfate appeared in the aqueous phase. The amalgam was drawn off and washed twice with 20 ml. portions of one normal sulfuric acid. Ten grams of potassium chloride was added to the combined washings and the reduced thallium solution. Titration with 0.1000 normal potassium bromate required approximately 7*5 ml. If the thallium (IH) was quantitatively reduced to thallium (1) the calculated volume of 0.1000 normal potassium bromate would be 10.1+3 ml* K. Bismuth Amalgam A three per cent bismuth amalgam was prepared by the same procedure used for lead amalgam by substituting Fisher Scientific Company bismuth metal for lead* The bismuth amalgam was stored under one normal sulfuric sold. Three 10,00 ml. samples of O.lOi+3 normal thallium (III) sulfate solution were pipetted into separatory funnels containing 100 grams of three per cent bismuth amalgam. The funnels were stoppered and shaken for one-half, one and two minutes and the amalgams were drawn off. The amalgams were washed twice with 20 ml, portions of one normal hydro­ chloric and the washings were added to the reduced thallium solutions. The combined solutions were diluted to 150 ml* with one normal hydro­ chloric acid and titrated with 0.1000 normal potassium bromate. The samples that were shaken for one and two minutes required almost identical volumes of standard bromate, while the sample shaken one-half bo minute required « smaller volume* two to ml. washings ©f the amalgam wore found to fee waffiMewi for the couplet© removal of thallium* three blanks was*© m is the following manner* Fifty aOL* of two nermal sulfuric acid wan added to 100 grams of bismuth amalgam and shaken for too mimtoo, the amalgam was drama off and washed throe times with $0 ml* portions of two normal sulfuric acid. 'fen grams of potassium chloride wee added to the solution which wee then titrated with 0*1000 normal potassium bromate* Xhe same procedure was repeated with one and 0.6 normal sulfuric acid* The respective blanks for two# one and 0*6 normal sulfuric acid were 0.03, 0*03 end 0*05 si* of 0.1000 normal potassium brcmate* Fire M B ®1* sables ©f the O*10li3 normal thallium (HI) adw* tion were treated with varying amounts of sulfuric acid and diluted to 50 ml* the diluted s&iqples were shaken in a separatory funnel with 100 grams of bismuth a*Baiga*n for two minutes. fhe amalgam mis drawn off and the aqueous phase was filtered through a Solas filtering crucible to remove globules of the amalgam* the amalgam was washed throe times with 50 ml* portions of one normal sulfuric and the filtered washings wore added to the respective samples* fen grams of potassium chloride was added to each sample, which was then titrated with 0*1000 normal potassium bromate using a Fisher Titrimeter equipped with platinum and calomel electrodes* A blank of 0*03 ml. of 0*1000 normal potassium bromate was subtracted from the volume of bromate used* the results obtained using a bismuth amalgam redaction ore tabulated in Table VIII. a TABLE m t m m m m SlBttguA Siidbw ot thoxzbm (in) to thallium (i) OBISO A BXfflflJTH AMALGAM ; AuftAMgr ©f Diluted Solution %' 8 It 3 Error (H«+) #aken 106.lt 106.lt 3M.it 106.lt 106.lt 80 * OOT: * 8o -1.85 Cd Zn *CCI♦2e -2n ♦2a 3e -0.65 -0.32 *0,356 *0.18, *0.250 *0.277 *0.h03 +0.763 t.4wgmnfl (38) reports tha redaction potential of thallium (I) to *win™. (0) at a dropping mercury electrode to be -0.217 volte. U2 the Increased mtm of redaction noted tear Hagans lo attributed to the large solubility of thallium metal in msreuzy* Xtt-a d d solution cadmium amalgam reduces thallium (I) to thallium (O)i, duo to the solubility of thallium (o) in mercury, Gblertde ions m o t tea absent when metallic redactors are used to reduce thallium ( I I I ) to thallium (t) , since the oojparation of the insoluble thallium (I) chloride from the metallic redactor la difficult, fh® results shown in fables t£% IV and y show that ih© cadmium, ■dtlwer and Memath radactora may tea weed for the <|aamiitabtv© reduction of preliminary' to its volumetric oxidation, These redactors gave ^uaniiiativ© reduction of 50 ml* of 0,02 to 0,006 normal thallium (TXT) soXutioiie* The results frcwi the silver apd bismuth redactors give arerage errors of 0*20, 0,25 and 0,1? n&lligrams respectively, These results correspond to average relative for cant errors of 0*39» 0*2? and 0*1? for samples containing from 30 to. 212 milligrams of thallium# laid concentration of iha solution may vary from 0,01 to one normal without effecting the coa^leteneo® of reduction* the rate of fleer through the redactors is dependent m . the surface area of the metal teeing used. These redactors ware prepared with finely divided metal and flow rates of 20 to 25 ml* par minute gave consplete redaction* Blank: corrections m the cadmium, silver and bismuth redactors of 0,05, 0,03 and 0*02 A * of G.IOOO normal potassium teromate were necessary, m e n determining thallium % the voimebfi© tercmate method, the m e of a cadmium, silver ©r bismuth redactor is superior to sulfur dioxide U3 for the reduction of thallium (HI) to thallium (I) * The blanks on the metallic redactors are smaller and more consistent than the blanks on sulfur dioxide* The time required for the reduction of thallium (XXX) to thallium (I) with a suitable metallic redactor is approximately five minutes* but reduction with sulfur dioxide and removal of the excess requires at least one hour* The bismuth redactor is preferable to the cadmium redactor* since finely divided high parity bismuth metal Is commercially available whereas cadmium metal must be machined to a small particle size* A bismuth redactor can be prepared more economically than a silver redactor* The erratic results obtained using the nickel redactor were probably due to the impurities in the nickel metal (Table in}* Blanks on the nickel redactor consumed from 0.02 to 0*22 ml* of 0*1000 normal potassium bromate. The redactor had a relatively small surface area and small flow rates were necessary to achieve complete reduction of thallium (IH) to thallium (I)* It is probable that a finely divided high purity nickel redactor would give a constant blank and would be suitable for the quantitative reduction of thallium (III) to thallium (I). The lead redactor is not suitable for the reduction of thallium (III) to thallium (I)* When sulfuric acid is used in a lead redactor the insoluble lead sulfate forms a film on the lead. The results in Table VII indicate that the lead redactor rapidly looses its reducing capacity. If the sulfuric acid is 2.5 normal in hydrochloric acid, hh the lead sulfate film nd.ll net fern* thallium solutions 2.5 normal In hydroohlorlo acid precipitate thallium (I) chloride which would be trapped in the lead redactor* the redaction of thallium (XXI) to thallium (X) using an aluminum redactor m e Slew* A 0*01 normal thallium (XXX) eolation that was 0*2 normal in sulfuric acid was not quantitatively reduced when a flow rate of 12 ml* p m minute was used* A 0*01 normal thallium (XXX) solution, that was one normal in sulfuric acid, m s quantitatively reduced by the aluminum redactor, hut hydrogen evolution was quite vigorous and some of the aluminum was forced into the redactor reservoir* the cine and Jones redactors are unsuitable for analytical use since they reduced thallium (XXX) to thallium metal* Amalgams are not convenient for the reduction of thallium (XXX) to thallium (X) due to the difficulty of separating the amalgam from the aqueous phase* When carrying out the reduction In a separatory funnel, the amalgam Is drawn off, hut small heads of amalgam remain attached to the glass wall of the funnel* fhes© heads of amalgam mat he removed from the aqueous phase prior to the volumetric oxidation, since they would reduce thallium (XXX) * Addition of carbon tetrachloride to separate the amalgam from the aqueous phase is only useful when manual stirring la used* Saturated bismuth amalgam gives a quantitative reduction of thallium (XXX) to thallium (X) In two to 0.6 normal sulfuric acid solu­ tions. $£* results in fable ?III Indicate consistently high results* 1£ Lead sulfate precipitates when lead amalgam is used as a reducing agent in the presence of sulfuric acid* The lead sulfate coprecipi­ tates thallium (X) sulfate and low results for thallium are obtained. X? Volumetric Determination of Thallium (I) Using a Standard Sodium Hypochlorite Solution A. Direct Method Sodium hypobromite is known to react more rapidly than sodium hypochlorite. Standard hypobromite solutions can be prepared extempor­ aneously by adding a standard hypochlorite solution to a slightly alkaline solution containing bromide ions* If the hypobromite Ion reacts rapidly, only a trace of bromide ions would be necessary! since the reduction product of the hypobromite ion is the bromide ion which could react with more hypochlorite to yield hypobromite. The oxidation of thallium (I) to thallium (XXX) by hypochlorite yields the chloride ion as a product and the precipitation of thallium (X) chloride would retard the rate of thallium (X) oxidation* In a solution containing lu2 grams of sodium nitrate per 100 ml., the solubility of thallium (X) chloride is Increased from 0*38 to 0*61 grams per 100 ml* of solution. 1. Salt Effect Titrations of thallium (I) with extenperaneously generated hypobromit© were performed with and without the addition of sodium nitrate. The addition of four grams of sodium nitrate to 100 ml, of thallium solution was found to increase the rate of oxidation of thallium (I) by hypobromite, thus increasing the potential change at the end point. U6 Xn the titrations of thallium (I) with csctej^eraaeously generated hyjK*br©®ite the solutions nape first treated with an inert salt In order to increase the eoinbility of thallium (I) chloride* The effect of pH on the rate of reaction between hypochlorite end bromide lone mas determined by* the fblXowing procedure* Measured quantities of thallium (I) solution were treated with 50 ad* of various buffare and diluted to 100 ml* Baeh:sample was treated with tai drops of a one per cent pot&esiua bromide solution, four grams of sodium nitrate, and titrated with a standard sodium hypochlorite solution, Throughout this section all efolvalenc© points were detested potantio~ metrically* by the use of a Sargent wide range potentiometer, equipped with a platinum and saturated calomel electrode system*, the titrations were carried m % by adding small increments of standard hypochlorite solution and waiting 30 seconds before the potential was measured* The change in potential, p m 0*10 »&♦ of standard hypochlorite at the equivalence point is a measure of the rate of formation of hypobromite* The pH values of the sample solutions were mmmmtd before and after the hypochlorite titrations with a Beckman Model a pH motor* The results ere tabulated in Table XX, and indicate that the reaction between hypochlorite and bromide ions is most rapid In the pH range from 7*0 to 8*5* Sodium bicarbonate m s found to be the most suitable buffering agent and was used throughout this section. hi TABLE XX EFFECT OF pH OH FORK&TIQN OF HXFQBROMITS FROM HXPOCHLORITE AND BROMIDE IONS ■wiwaa^teww TmaiwHB Buffer 1% NaHC03 2% NaHC03 Phosphate Phosphate Phosphate Borate Borate 1$ Ka3G03 i n Horn (!) (2) (3) (1) (2) tm Before AfSar 7*73 7,73 6*50 7**8 7*23 7.68 8.29 10.93 ** 8.00 8.0? 6.50 7.12 7.19 7.63 8.11 10.80 Change in Millivolts per 0.10 ml* of 0.1 B 010“ 97 95 29 18 28 53 b5 ■m+* 3, Effect of Sodium Bicarbonate Concentration The effect of the sodium bicarbonate concentration m s determined in the following manner. Four 10.00 ml* samples of thallium (X) nitrate were diluted to 100 sriU and treated with four grams of sodium nitrate and ten drops of a one per cent solution of potassium bromide. One, two* three and four gram portions ©f sodium bicarbonate were added to the respective samples. Titrations were carried out using O.IOBO normal sodium hypochlorite. The results of these titrations are recorded in Table X. The results in Table X indicate that thallium (I) solutions contain­ ing bicarbonate concentrations of one to three per cent respire nearly identical volumes of standard hypochlorite. The change in potential at the equivalence point appears to increase as the sodium bicarbonate concentration is increased from one to three per cent* The largest 1*8 tpa X 9 B C T OF SODIUM BICJIHBOJMIB COJCEtmiAflOH ON THE o x m m o N of m m z x m (D bt hxpobrcwite 0»miccntor*at4o& Cfaa&g© la itllllvelts MX. MmigPWM lhaXliwa Srror of Sodium 0.10 nl. of 0,1 H CIO" 030 fakon Found (Mg,) Bicarbonate Hejj. , ,> 1 11. . I I .i HHl i n Will III 91 2 9,11* 102.2 9,10 102,2 "IMP!*... error III HI 11 | • mm— 905 M»*» 126 300 IM«I»II|W I i 9.15 302.2 100 3 I* I ' Hi l f**'*1 — -I. 1W.WII II* 101,0 -1.2 3«U0 *1.2 100.9 *1.3 100.5 *1.7 I■ll'MW».<1«Wl«"H '"<«".I*!. '."’ mm found la eolations «seHsto3*to« four per coat sodium bicarbonate, la the following work la tele section two per cent sodium bicarbonate eolations were used. nail The effect of bromide lea eoBoeatraiien on the oxidation of thallium (1) by a sodium hypochlorite titration mm estimated In the following manner., Two 10.00 A . sarnies of 0.10U8 noraal thallium (I) nitrate were treated with toe grams of sodium bicarbonate, fear grans of nitrate and dilated to 100 ml. To one sample was added ten drops end to the ether 50 drops of a one per seat eolation of potassium bromide. These se*®lea were titrated with 0.1080 nouaal sodium hypo­ chlorite by adding email increments and reading tee potential at regular ♦«,». intervale 'wtti successive values agreed to within five millivolts. Within 30 awiwtdif after the addition of one ml. increments, tee potential values were constant bote solutions• Mhen within 0.3 ml, from the h9 e^Etvalenoe point, the waiting %im was 90 e m e n d s ter the solution sentilnlmg 50 drops m d ItO seconds for the solution containing ten dP«$S, Another sample m o ran in a similar manner, except m erne par cent potassium bromide mao added, drop of titrating this sample, ememstl M m d m were retired before constant pot^tiaX *dues were obtained, the investigation on the cfftost of bromide ion concentration indicates that ten drops of a one per cent potassium bromide mention ere- sufficient to give a rapid conversion of hypochlorite 'to hypebron&te* fhorou^wmt the remining work in this motion t m drops of n m per cent potassium bromlde solution sere need# Having; established the tnwesr oR and the wtatftiaamtt bromide ion con** eentr&tion which sere necessary for a rapid oxidation &t thallium (I) to thalliuia (XXX), a naa&er of samples sore run using the following . procedure* Measured thallium (X) samples sere diluted and treated with sufficient sodium bicarbonate to yield a ts© per cent solution and sufficient sodium nitrate to yield a four per cent solution,* Bach sample was treated with ten drops of one per cent potassium bromide solution for each 1X30 «&* of diluted velum®. The samples ware titrated with standard sodium hypochlorite by adding small increments and waiting one ralmt© before measuring the potential. The remits are tabulated in fable XI. The change in sciential during a titration of thallium (X) by hypochlorite is shorn in Figure 1* This titration was carried out by CM oo CD ‘3*0 S lO *SA S110AIT1IW ro OF CO THALLIUM (I) SODIUM W TO SODIUM HYPOCHLORITE HYPOCHLORITE 00 I. TITRATION NORMAL CM FIGURE 0.1081 O ML. OF 50 51 mam tw m tm m m m m (i) imn mmm® S0DHJM HXFOOHUmTTB SGOTIGH& ■6885 Wees SHuted 7q1i^I0 (H3-.) liWipiii (Ml;) m nnww' ^i |w>»ii*1B»i a 3 k 5 100 »« 101.8 102,2 0.1082 J01.J* 1(3.2 6*1081 102.2 102,2 0,1061 102.2 107.1 11.90 0.1081 0.1081 0,. 0.1081 11.98 6*3082 22.91 0.1082 0.1081 0.1081 0.1081 0.1081 9. 100 100 f 8 9.63 9.88 9.85 5 10 n 12 13 Ik 15 100 100 100 100 850 Found .j i tmuii’ aiI»awi>*f»inin, 0,1082 0,1038 9.6© 1 Tafcea 28.86 jgUSk' 22*99 21t,02 132.6 133.6 *0*8 0.0 101.3 106.U -0*8 *0,7 **0*1 102.2 131.lt 132.5 *^1*2 *0**1 101.U 102.5 «K.f «S«4 255,9 CHg.) 253.1 *3*2 *a*8 ♦k -*1*8 adding small increments of sodium hypochlorite and measuring the potential at regular time intervals until constant values m m obtained, Hoar the e^odvalenee point a tea minute stirring period m s VMNp&imdt to obtain a constant potential. Measured <|iiantitlea of 9#98 n£L, of G*X0k3 normal thallium (HI) sulfate eolation were treated with sulfuric acid, dilated to $& ml.* and passed through a oadaiam or silver redactor* The redactors were washed with dilate acid and the washings were added to the reduced thalliam eolation# These were partial^ neatraliaed with two normal 52 eodium 'hgtimmSM and breetot:I sitfc sodium bicarbonate, sodium sulfate, iBd t a M M s leas as prwi.m*3& described* The thallium {1} m s ^ peteniicmmrtri© titration t&tfe. 0.1077 nanaal sodium hypo­ chlorite* Tk© results are tabulated t& fable! XU, the cadmium redactor indicate that The results sd.th mm &fthe thallium (I) islest* Since cadmium precipitates m the carbonate or the hydrc»d.d© ©hen. the solution is made alkaXtn© some of 'the thallium (I) may he lest hr e©«* precipitation, The messpected remits obtained -with the silver redactor id.ll be discussed later, WASH?e IfW BIKES? BttOtMBI*® ¥TTa*?roMa @* ’ nmi.'nm (j) asBdcim b t ramtxc rbductoks Redactor Used Acid normality Before Reduction ©oh Gadrainm Cadmium Cadsdum Silver ©ok 0*00 0,01 0*©1 0'*0 Milliliter* of 0.107U Sfowal Hypochlorite Taken 9.1*6 9.39 9.50 9.50 9.58 19*1® l©6*k X00*k 10d*:l& &©&*k 106,h V** Error T».fi row (Mg.) 1C%»3 103.? 10U.8 lOlj.8 105.6 810.6 -2,1 *4*7 *1*6 —1 *6 ■*0*0 *1©M fb* OBddatlou of tiuOliwa (I) by hypoohlorita Is alkalis, arn&a is too olow for « divoot titration with nodf-a® bypeeMUwite. It was thought that as cnmasa of standard aodtua fcypochlorite could bo added 53 to a thallium (I) solution and upon standing the unreaeted hypochlorite could be determined by a titration with standard sodium arsenite. The oxidation of arsenite by thallium (XII) oxide should be negligible due to the slight solubility of thallium (XXI) oxide* 1* Time Required for Oxidation of Thallium (I) by Excess Hypochlorite The following procedure m o used to determine the time repaired for the complete oxidation of thallium (I) by an excess of sodium hypo­ chlorite . A 19*97 ml* sample of the 0.10U8 normal thallium (1) nitrate solution was diluted to 250 ml. and treated with six grams of sodium bicarbonate, nine grams of sodium sulfate and 1*9.88 ml. of 0*10X1 normal sodium hypochlorite. The solution m s stirred with a magnetic stirrer* The potential was recorded as a function of time. It m s found that one hour of stirring was repaired to obtain a potential above 700 millivolts. O m hour of stirring m s considered sufficient, since a two ml* excess of ©odium hypochlorite in the direct titration of thallium (I) (Figure 1) gave a potential of ?1© millivolts. 2* Determination of Thallium (I) Measured quantities of the 0.101*8 normal thallium (I) nitrate solu­ tion were diluted and treated with sufficient sodium bicarbonate to yield a two per cent solution and sufficient sodium sulfate to yield a four per cent solution* To each solution was added 1*9.88 ml* of 0.101U normal sodium hypochlorite* After stirring the solutions for one hour the unreacted hypochlorite was titrated with 0*1000 normal sodium arsenite. The results of these determinations are tabulated in 5U table XIII* A plot of on© of theee titrations i© given In Figure 2. TABLE XIII INDIRECT DET^miNATIQN OF THALLIUM (I) BY SODIUM ARSENITE BACK TITRATION OF EXCISE SODIUM HYPOCHLORITE Volume of Dilated Solution -__ 08*1 150 300 300 230 300 300 300 300 300 Milliliters of Arsenite Required fftllfssramB of Thallium Taken '' ” Found Error .. (Mk «)... to.10 37.91 37.88 35.1P35.33 33.67 33.65 29.83 29.83 107 a 129.9 129.3 155.3 155.3 173*6 173.8 213.9 213.9 I07.I 129.5 129.8 155.0 355.9 172.8 173.0 212.2 212.2 0.0 +0.5 “0*3 +0*6 •0*8 **0.8 -1.7 -1.? 3. Determination of Thallium (I) After Using; Metallic Redactors Measured ©supples of 9*98 *&* of Q.10U3 normal thallium (HI) sulfate ware acidified, diluted to 50 ml* and passed through metal redactors* The redactors 'were washed and the washings were added to th© reduced thallium solutions. The combined solutions were neutralised, treated with six grams of sodium bicarbonate, nine grains of sodium sulfate, and diluted to 300 ml. To each sample was added 1*9*88 ml* of 0.101U normal sodium hypochlorite and the resulting solutions were stirred for one hour. The unreacted hypochlorite was then titrated with 0.1000 normal sodium arsenite. The results of those titrations are recorded in Table XI?. co OJ oo CD CD 3 0 'S LO *sa [<) OJ s n o A m iw OF OJ TITRATION EXCESS OJ SODIUM HYPOCHLORITE ARSENITE OJ SODIUM oo NORMAL OJ 0.1000 ro OF ro FIGURE 2. ML CO 56 TABLE XIV t m m m t m t M x m of tkallxhm (x) % m m m & m metaixic rotjctors Redactor Acid tTsed Hc«ality Before Cadmium Cadmium Silver o*b 0*01 0,u Milliliters of Arsenite Retired 15*55 15*30 15.55 Milligrams Thallium Taken T l' Found Q.106k O.106U 0.106k 0.1186 0*1197 0*1161 Error (Mg.) +12,2 ♦13.3 + 9.7 0* Discussion Th© rat© of oxidation of thallium (I) by sodium hypochlorite in alkaline media is slow and the reaction is act suitable for a direct titration* Since hypobromite reacts more rapidly than hypochlorite* a direct titration of thallium {1} using hypobromite was found to be satis­ factory when carried out under the proper conditions* Th© extempor­ aneous preparation of hypobromite from hypochlorite and bromide was found to be pH dependent. The reaction m s found to be rapid between pH values of seven and nine (Table IX)* Sodium bicarbonate m s found to be most convenient for maintaining the proper pH, Concentrations of sodium bicarbonate of one to four per cent by might were found to be satisfactory. Only a small amount of bromide ion was found to be necessary since the bromide ion is returned as soon as hypobromite reacts with thallium (I)* The experimental work indicate® that one milligram of bromide is sufficient for th© rapid oxidation of thallium (I)* when a 0,1 normal sodium hypochlorite solution is used as a bitraat. 91 When sufficient bromide ions are added to convert all of the hypo­ chlorite to hypobromite* thallium (I) bromide precipitates and the rate of oxidation of thallium (I) by hypobromite is decreased* The addition of an inert salt ouch as sodium nitrate or sodium sulfate increases the solubility of thallium (I) chloride thereby increasing the rate of reaction between thallium (1) and hypobromit©* The data in fable XI on the direct titration of thallium (I) with hypochlorite indicate that this method yields consistently low results. Since precipitation from a more dilute solution tends to decrease the amount of coprecipitation, one would expect to obtain better results by titrating thallium (I) in more dilute solutions* Samples 11 through lU in Table XI* which contained nearly the same amount of thallium* were diluted to different volumes and titrated with a standard hypo­ chlorite solution. Samples 11, 12 and 13 were diluted to 100 ml* and showed negative errors of 2.2, 3.2 and 2*8 milligrams of thallium, while samples Ih and 15 were diluted to 250 ml. and showed negative errors of 1*8 and 1*9 milligrams of thallium. The consistently low results in Table XI appear to be due to coprecipitation of thallium (I) by thallium (III) oxide* The data in Table XIII on th© indirect determination of thallium Indicate a trend toward low results with increasing amounts of thallium. Coprecipitation of thallium (I) by thallium (III) oxide is probably responsible for the low results obtained, k maximum error of 0.8 per cent can be expected for th© indirect determination of 100 to 200 milli­ grams of thallium. The change in potential during a typical indirect titration of thallium (I) is shown in Figure 2* £0 Considering th© war&al&ee of pH, bromld© ion etaiceairation sad the solubility of thallium (I) halides th© following procedure 1© x w m M N M ’for the direet volumetric deiars&natim of thallium (1) *»iag as a standard oxidant. Dilute © solution of thallium (X) to 300 ssl, this solution mast he free of substances that would precipitate er reduce tta&XiM (..XXX), reset with hy^ehloriie or hypebroatie or palpitate thallium (I) in alkaline eoXution* HastraHe© the solution and add Sbc grams of eodiwm bteaxbon&io* mime gems* of sodium sulfate and one »&* of a ©iis per seat petassiwra bromide solution.# titrate the solution hgr sodium lypoehlorii© solatia* **0 ^ ^ 1.1 & standard Measure the potential in the solution with a ittrimeier or |ietestic^seter e^aifped with a electrode system* the selufciom should he vigorously stirred for 3© ettreiftdtt after1tha measured* of each before the potential 1# the equivalence point is detected by a change i» potential of appreximtely 10© aslllirolts per ©*1© ml# of ©*10©Q normal sodium hypochlorite added.. W m the indirect determination of' thalliM (X) using m arsenite titratdon of excess hypochlorite the following procedure is roeoraraanded. Dilute a solatia of thallium (X) to- 3©# ml* f M m eolation meat he free of subsume© that would precipitate or reduce thalliwm (XXX)* react with hppoohlorite or precipitate thallium (X) in alkaline solution* neutralise the solution mad add six grams of sodium bicarbonate and grass of sodium sulfate, M d a measured ro3iwato3y 300 ad,iliyoitaf the direct .and indirect methods give equally accurate results with a maximum error of apgaroximaiely 0*8 per cent for 100 to 200. milligram thallium aaaqples, jftn advantage of the direct method is that it is more rapid than the indirect method due to the one hoar of stirring repaired in the latter. However, the titration in th© indirect method is m m rapid due to the instantaneous reaction between hypochlorite and arsenite, idaHe the reaction between hypobromite and thallium (!) is mmmfaat slower, the in. potential at the eguiralei^e point Is larger in the In** direct method thereby allowing a more accurate estimation of the and point* fhe indirect method has the disadvantage that two standard solutions are required whereas the direct method requires only ene standard solution* a minor advantage of the indirect method is that arsenite is used m a titrant -where the direct method requires an slka~ line solution of hypecia^rite* m m a eolation containing thallium in the f&us three cedLd&ilon state is encountered a reduction of ihalliumflll) to thallium (I) is necessary before a titration with hypochlorite can be performed. Sulfur di©2d.de can be used to reduce thallium (HI) since the excess can be removed and the reaction product is the sulfate ion which dees not interfere in the titration. Hetallie redactors and mtik&m safe not satisfacto ry fa r the redaction o f th a U is * ( IH ) to th alliu m ( I) j when & titra tio n la* a lk a lin e solution i t to bo used, these redactors introduce metal Iona to the system* which p re cip ita te tdwrn the s o la tia in made alkalin e fo r the titra tio n * ffee e ffe c t o f these preolpitateo depends on whether the d ire c t or in d iro o t hypochlorite method is used fo r the deterw i»M o*i o f thallium ( I ) . In the indirect detmdnation thee© precipitates appear to catalyse the deeofipoeition of the excess hypochlorite, this decomposition of hypochlorite yields high reedte for thallium as in table XI?* in the d ire c t deteriidjQation the cadmium hsdroride o re cio ita te appear® w y I V i *** fO f*-. J l tffSlUfeJlihiMi *1 J f « * ; | u in a silver redactor gscv© unexpected results (Table X U ) . Th® th^lrl-fv88sample consumed nearly twice the calculated volume of hypochlorite expected. Each miHiequlvi&eui of thallium (HI) reduced introduces a millieqoivaleat of silver (I) ion#- which precipitates m th® carbonate npon the addition of sodium bicarbonate, fhe result obtained suggest that silver (I) may be oxidised to silver (XX) by fcypobromlt© in a s u b t l y alkaline scXutiem* ?. Gravimetric Determination of Thallium Using Sodium %pochlorite 111© gravimetric determination of thallium as thallium (XIX) oxide is based on the alkaline oxidation of thallium (X) to thallium (XIX), which precipitates as anhydrous thallium (XXX) oxide* Potassium 61 ferricyantde im tbs only oxidant proposed for the gravimetric determine ati ssi Q r-4 H O U\ O CM \A CM Q * U 238.8 247*0 235-8 247.3 ’245*0 244.5 238.6 240.* *37*3 2Mia6 244,0 236*8 240.4 237*5 n w base, Bower* r , staples containing 20 and 25 nil* o f on® normal aodlua hydrescida gvre almost Id e n tic a l p recip itate weigrissi therefor® , s ix washing* 'war® considered reasonable, the data is Table 171 on the e ffe c t o f a lk a lin ity in d ic a te , th at the m ights o f thallium ( IS ) oxide p recip itates increase K ith Inereaalag a lk a lin ity . However, p recip itates mere mm denee when formed in stronger alkalin e eo latio n , fo r i t is apparent th at in statin g a procedure & compromise aost be made between the a lk a lin ity o f tha p re c ip ita tin g eolation and a reasonable number o f washings. The data in Table IT S in dicate the degree o f interference exhibited varies * foreign Ions. Warn foreign Iona sere added to the alkalin e 68 thallium (X) solutions no noticeable precipitation occurred. Solutions Q.OX molar In aluminum and 0*001 molar in gallium did not interfere. In the case of zinc, a more basic solution was required to reduce interference. Solutions 0.001 molar in zinc and one normal in base Care a one per cent positive error in the determination of thallium. Solutions 0.01 molar in phosphate do not interfere, larger concentrations of phosphate do not interfere but tend to disperse the precipitate making washing difficult. The data in fable XVIII indicate that thallium (IU) oxide dried under nitrogen exhibits a slight increase in weight when heated in air. Thallium (HI) oxide, when heated above 100°G., is reported to begin decomposition to thallium (I) oxide with the ©volution of oxygen (21). The increase of weight by heating thallium (III) oxide is reported to be due to the absorption of carbon dioxide by the thallium (I) oxide. Considering the data on the washing of thallium (XXI) oxide, the alkalinity of the precipitating solution, the interference of foreign ions and the effect of air drying, the following procedure is recommended. neutralize a solution containing not more than 200 milligrams of ».fraTHt«a and dilute to 350 ml. Add 25 ml. of one normal sodium hydroxide and filter. Add 25 ail* of Clorox reagent (prepared by diluting 30 ml. of commercial Clorox to 150 ml*) and digest the solution for two hours. Decant the supernatant liquid through a tared Gooch crucible and wash the precipitate six times by decantation using 80 ml* portions of hot water, Transfer the precipitate to the crucible and dry for one hour at 200°0, in an atmosphere of nitrogen. The results for thallium will be approximately one per cent high. ft appeared that sodturn hypochlorite woald be sore suitable than petaselem ferricyamide for the gravimetric determination as thallium (HI) ©adds* However, the- results obtained indicate that sodluia hypochlorite offers m© advantage mm potaasitm ferricyanlde far the alkaline oxidation of thaUicm (I) to Thallium (HI)* The thallium (HI) oxide precipitates obtained by using potassium ferric cyanide are more dense and more easily handled, than precipitates obtained by using sodium hypochlorite* the density and ease of handling the precipitates appears to be related to the color of the thallium (HI) oxide.* The darker colored precipitates are more danse ami easier to handle* In the section on metallic redactors the chrornate (30) and the potassium ferrieyanide (ho) methods ware need to analyse a standard thallium eolation* The results from these standardizatlone indicate, 'that the chromate and ferrleyanide procedures yield more accurate results than the sodium hypochlorite method* 71* m the Precipitation of fkmltern ( U I) Oxide by Potassium Ferricyanlde The gravimetric determination of thallium by the fssrieyamide procedure of Hack end leppev (h0) appears to be aeperier to the gravi* metric ohromate method (30)* The ferricyanide procedure does not define interferences or the specific conditions for precipitation* Ho state* meat is made concealing digestion of the precipitate or precipitation from a hot solution* Concerning interferences' the procedure states 70 that ©laments forming alkali Insoluble ferricyanidos or ferroeyanides mast be removed prior to jHfeolpttabicm* «*f®et of pp«oi|»iiatiJag thallium (fix) oxide from a hot ©<&»*** ttoa and digestion of the preaipitat© mas studied in the following mmsr* Twelve 19.97 A * sables of 0*101$ normal thallium (2) strata eolation w o diluted to ?0 a!* aid treated with 25 ml* of one normal potassium hydroxide* Six of the samples wore heated on a steam bath before precipitation see made by adding 25 ml, of an eight per cent potassium ferrioyanld© solution# The six preeipitatos formed in hot solution w e digested for two hours* the remaining six saisplos sore treated, ulth 25 ml* of the eight per sent ferricyanide* These samples mere precipitated at room tejsperature and no digestion mas made* The potassium hydroxide and ferrieyanid© solutions mere freshly prepared and filtered before being, used* After standing Id hours the twelve precipitates mar© ©ash mashed six. times mith 50 ml* portions of hot mater end transferred to bared Oooeh crucibles* The thallium (HI) oxide precipitates mere dried under a nitrogen atmosphere for one hour at 2QQ°C* The results of these precipitations are given in Table XIX* The 0*10143 normal thallium (HI) sulfate solution mas assayed by the thallium (222) oxide procedure (UO)* Precipitations mere © a m © d out at room texaperatur© and the precipitates mere not digested* Five 19*57 ml* sasples of the thallium (2X1) sulfate solution yielded 71 TABLE XXX btoct or raacjpiTATijromm hotsolutionado BlffiESTIOH OF THE PRECIPITATES WinmtaSIWSSWeewwsweweswimssessweeisaiBeswiiBeeweawBesweBamsiumaemW Digestion. and P recip itatio n P recip itatio n from Cold ' Ion and No Digestion :w 21U.2 211*.1* 213.3 2U*.0 215.1 23li.O 213.9 213.9 213.9 213.9 213.9 213.9 *0«J ♦0.5 *0,6 ♦Owl ♦Owl 213.9 213.9 213.9 213.9 213.9 213.9 212.1* 212.5 213.2 213.5 213.2 213.2 •*1*5 *0*T *0*1* *0*? p recip itate# o f thallium (IH ) oxide weighing 0.2399, 0.21*06, 0.2398, 0.2399 and 0.2387 grams. Assuming Abe thallium (TJX) su lfate to he 0.101*3 normal the calculated weight o f p recip itate# should he 0.2377 grams. The p recip itates were easily dispersed by washing .and d iffie u lt to handle* Two 19*97 m l. samples o f the thallium (X U ) su lfate eolation were assayed % the thallium (XXI) aside procedure. P recip itatio n was carried oat in a hot selntlOB and the p recip itates were digested two hours. This m odification o f procedure yielded t halliu m (IXX ) amide p recip itates weighing 0*2388 and 0,2383 grams, giving an average erro r Of plus 0 .8 Mfc n gramB o f thalliu m (J2X> amide. The** p recip itates dispersed m was&lAig a«d were d iffie u lt to handle. S i* 19,97 m l. samples o f the thalliu m (H Z ) su lfate solution were reduced by h^vn*>e s u lfu r dioxide through the solutions fo r ton minutes. n After standing over night on the steam bath to remove excess sulfur dioxide, the sables were mote alkaline ty adding 30 sdU of filtered one normal potassium hydroxide* Freeifitation was carried oat by adding 25 uSU of a filtered eight per east potassium ferrloyanide solution to each sample. Those hot solutions uere then digested for two hours* After standing 16 hours the precipitates sere washed sis times by deeaniation, transferred to tared Gooch crucibles, and dried under nitrogen for one hoar at m f $* the saints of thallium ( m ) oatlde i w e 0*2386# 0.23$*# 0.23?5f 0.2388# 0.23$* and 0.2368 grans, giving an average error of plus 0.8 milligrams* the precipitates danse, easily handled, and did not disperse on sashing. A study of the interference of foreign loss was mad© in the following manner. Samples of 13*97 ail* of 0.10U8 normal thallium (I) nitrate solution were dilated to 50 e&# and made alkaline with 25 ml. of filtered one normal potassium hydroxide. Measured quantities of foreign Iona were added to the solutions* Precipitation m s carried out by adding 25 ml* of a filtered eight per sent solution of potassium ferricyantde* The precipitates sere digested Shout two hows on a steam hath and allowed to stand 18 hours before filtration, the precipitates were washed sis times by decantatlon with 50 nil. portions at hot water, transferred to tared Qoooh crucibles, and dried for one hour under nitrogen at 20O°O. The results are tabulated in Table XX. 73 xx effect or forbioh ternsas the mcmmmrzm gf msu*xtJM By TBS POTMBJRffi FEmXGTMWM U M O © Ion Added UllW^TtnrW Zinc Zinc ©allium Hilli- Diluted Fotaesium am .A------jl ^ i— yx ai'^oc&ac g»»»a Yolwsa i C<85£. , 27 65 65 5.5 11 100 100 10© 100 100 0*25 OstS ©*iS O.liQ o *U© 7ak«tt FcraiHi 213*9 m*9 213*9 2X3*9 213.0 272.7 270.9 213*3 213 #1 tew