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This investigation was undertaken to detemine the boiling points, compositions and densities of HBr solutions distilling at pressures of 750, 760 and 770 mm.of mercury respectively. Experiments in this laboratory by Ewing and Shadduok3 have shown that the composition of HBr distillate at 760 mm. pressure is constant. Work with this material by other workers has shown a variety or results. Leger5 reports the boiling point of 3131' at 760 mm.pa:essurs as 127° and the composition of the distillate 48% HBr. Carriers and Cerveau‘1 give a boiling point of 126° and a composition of 47.5% m for the distillate at 760mm. pressure. A. Bineau6 thoxght the constant boiling acid was the pentahydrate having a composition or 47.43% HBr. Roscoe" disproved this by distillation of the HBr solution at two widely separated pressures. At '760 mm. pressure the acid boiled at 126° and showed a composition of 47.86% HBr. At 1947 mm.pressure the sane sample of acid boiled at 155°C and had a composition or 46.3% HBr. A review or this range of values lends its support to the advisability of a re-determination of some ,1g’haa‘hcfz-MWJ ' fl .. .‘Jf‘lij ( l of the constants concerned by precise methods. Experimntal Work Preparation of Materials Water; Conductivity water was used throughout this investigation. Hydrobromic acid; The best commercial grade or Baker's Analyzed acid containing 34 per-cent of BB: was used . It was purified by fractional distillation. Five distillations of the acid were made. These were carried out in an apparatus similar to that used in the deter- mination of the boiling point. The glassware coming in contact with the HBr solution with the exception of the thermometer was pyrex. No other material except air came in contact with the acid. The 1000 ml. distilling flask with a ground glass stOpper and sealed to a condenser was charged with about 800 ml. of the HBr solution and after the system was sealed its pressure was adjusted to 760 mm. of mercury. The distillation was carried out at this pressure which was constant to within 1 .2 to .3 mm.of mercury. When the boiling point of the acid had reached 124° a second receiver was supplied. The HBr solution distilling off at 124° to 124040 (uncorrected) was collected. As the temperature began to rise toward the end the distillation was stepped, the system recharged with mare acid and the procedure repeated. When the acid had been completely worked over the first fraction to distill off was charged back into the flask and worked over again. This being completed the residue was discarded, the flask rinsed.and.the procedure repeated using the fraction of distillate from 124° to 124.4°. End portions, the first to distill off and the residue left in.the flask were discarded. The distillate with a boiling point of 124.4° was retained.and a third, fourth and fifth distillation was carried out in a like manner. This gave a distillate of HBr clear as water. The final portion having a boiling point of 124.4° was considered sufficiently pure for this investigation. It was stored in a carefully cleaned brown glass steppered bottle, which had previously contained HBr solution, until needed. Silver nitrate;.A commercially pure grade of Baker's analyzed silver nitrate was used. It showed no turbidity when a portion was dissolved in a small volume of water. A.fivc per-cent solution, by weight, containing three m1. of concentrated nitric acid per lOOOg. was prepared, allowed to stand overnight in a covered container then filtered through a carefully prepared asbestos goech crucible. Nitric acid; A.commercially pure grade was used. This acid showed no turbidity when treated with silver nitrate. Asbestos; Asbestos fiber of good.quality was digested in 20% hydrocholoric acid for two hours on a steam bath, then filtered.and washed until free from chlorides. -3- It was suspended in water until needed. Thermometer; An anschutz thermometer was used. It was graduated to read .20 and had a range from 85° to 160° . Barometer; The barometer was of standard weather bureau type. Distillation apparatus; The distillation flask, con- denser, receiver and manometer were similar to those used by Foulk and Hollingsworthz in their investigation of hydrochloric acid solutions. One end of a 2.9 cm pyrex glass tube was constricted slightly about 2 cm.from the end. The lower end of a heavy wall pyrex test tube was heated, tapered and drawn slightly so that it fitted the constriction in the 2.9 cm tube. This Junction was then ground to a perfect fit. A short piece of glass rod having an eye in the end was sealed to the lower end of the ground glass stopper. A hook was fashioned in another piece of glass rod placed through this eye and sealed together thus giving a flexible Joint. The lower end of this glass link was so shaped that it would slip under and around the bulb of an anschutz thermometer suspending it freely in the tube. A 500 ml. round bottom flask was sealed on the base of the 2.9 cm. tube. 9 cm. from the flask a distilling arm was sealed on the neck. This arm was in turn sealed to the pyrex core of a condenser, leading to the receiver containing small sample bottles .4- for'thc collection of samples of the distillate. The condenser and flask were painted black with the exception of the neck of the flask above the distilling arm. The budb of the flask was also covered with a paste made of sheet asbestos and water. This dried well and formed an efficient insulation which aided in main- taining an even temperature and preventing bumping during distillation. An ebulator made from.a piece of pyrex tubing;and pyrenglass beads were also used as insurance against. bumping. The neck of the flask above the distilling arm was wrapped.with asbestos rope. .A short open space being left for the reading of the thermometer which was sus- pended so that its bulb hung about 4 cm. below the distilling arm. The pressure regulator consisted of a bottomless glass bottle sinkered with a sufficient quantity of lead to cause it to sink to the bottom of a 20.5 by 46 cm. glass battery Jar filled.with water. The neck of this bottle was fitted with a one hole rubber stepper and.a stopcock. The bottle was suspended by a wire over a pulley above. The opposite end of the wire was loaded with movable weights so that by adding more or taking off some the bottle could be raised or lowered thus exerting the desired effect on the pressure of the system to which it was attached. A small amount of friction was necessary for the proper functioning of this device. The stopcock was connected by means of rubber tubing to a T tube one end of which connected to a manometer, me other end to the receiver for the distillate. Pycnometer for dmsity determination; The pycnometer was of the vacuum type made by sealing a marked capillary tube to the bulb of a 50 ml. pyrex distilling fled: and sealing on at the other end of this capillary a stock having a ground junction to fit a filling device and a cap to prevent evaporation. Procedure. Five anall weighing bottles and a 150 m1. beaker were placed on the movable base in the receiver which was then sealed, its lid being held in place by two small clamps. About 400 ml. of the pure HBr solution was placed in the distilling flask which was heated with a burner. The barome tcr reading was corrected and the pressure in the system regulated by the control to 750; 760; or 770 mm of mercury on the EBr solution. As soon as the distillation was well under way the pressure did not vary unre than :t. .2 to .3 mm.cf mercln-y. The pressure was watched carefully and the boiling point was noted each time a sample was collected. When the 150 ml. container was nearly filled with the distillate, two or three or more samples of from -5- 3 to 4 ml.each were collected. Then.the flame was removed, the pressure was rele seed, the stoppers placed in the weighing bottles, weighings made and.the samples analyzed. Part of the work was done by this procedure, then it was found expedient to vary the method slightly so the density might be determined from the sane dis- tillation. One 100 ml.beaker and cm 150 ml. beaker were placed in the receiver 125 to 150 ml.ef the HBr was distilled off then a 100 ml.eample was distilled .and collected in the second container. Two portions of this sample were transferred.toweighing bottles for analysis and the pycnometer was filled with a portion of the remainder, brought to constant temperature by allowing it to set overnight in a thermostat at 25.05° 0. The content of the pycnometer was then adjusted to the mars by means of a capillary tube. Excess HBr solution above the capillary was wiped away and the stopper cap inserted. The outside of the pycnometer was dried, the pycnometer placed in a dessicatcr for 10 minutes then weighed. Barometric pressure and temperature were recorded for tea later in.calculation of the density. In filling the pycnometer was evacuated by a water pump, a charge of'the acid.allowed to flow in, nearly enough to fill the pycnome ter. The pycnome ter was -7- again evacuated until bubbles ceased to come from the HBr solution, then HBr solution was let in slowly until the bulb was filled. The small bubble remaining at the top of the flask was removed by warming the pycnometer in his hands until expansion of the contents expelled it. On cabling to 25.0500 in the thermostat the pycnometer was completely filled with air free HBr solution. Analysis; The samples of HBr weighing 4 to 5 g each were diluted to 800 ml. in tall form liter beakers. Slightly less than the theoretical amount of 5% solution of silver nitrate was added slowly with stirring this operation being carrie d on in the filtered light of a photographic dark room. The samples were covered and allowed to set for twelve hours then a _ slight excess of silver nitrate solution was added and finally 5 ml: of concentrated nitric acid. Complete precip- itation and rapid settling followed this treatment. After standing twelve hours the silver bromide was filtered ' onto platinum gooch crucibles which had been previously treated by washing with dilute silver nitrate then with water until entirely free from silver nitrate dried at 110° overnight then at red heat to constant weight. The Ag Br was washed with about 1 liter of conductivity water dried overnight at 110° then finally heated Just to the fusing of the Ag Br. They were then cooled .3- in.a dissicator and weighed. Treatment was continued to constant weight within 1;.0002 g.All weighings were:reduced to vacuo and a.correction of .54 x 1063 of Ag Br added.for each liter of solution plus wash water used. The factor used for conversion of this weight to the equivalent of HBr was .43091. mmmp.m Hom~.m Hmms.w Ost.m meN.a wan~.m hpaaswhoz :He.ss mee.ss ij.N: mm~.s: mms.~j mes.ss mm~.ss men.me mm~.~: www.ms Hm m e.pe mmmmm.m omnmw.~ mmmma.w mmoms.m meeem.s mmmms.m adsomb am am as .pt eases.s momse.e smemm.m fimwmm.m oommo.m mwnsm.m moswm.s smwsm.m omom:.: stmm.s assomb mm Adfiomv am m . A.EE own mndmmonmv .H mqmwe .2 IL. ehassaemas mm eeeasapehe as o mmflsom speasaemae em seessapeae as m moanom onwfimos Mm opaaflapese em epsssspene as opaashemae om oesassseae pm eesHHapass as 4 mossem -10.. oi u\ \o m N\ r~ l\ ‘60 mass. meme. mmnn. emms. mama. seen. moan. mmew. duo (‘1) \‘\ ) Yr ('0 a; a") w E0 tl\ thHdFHO HNN.N: mi. 3 mee.ss nos.ss mmw.sn mms.ss mms.s: mam.sn smm.sn Ham.ss am 5.? ..r a. CH C 3 ‘60 60 f.~ N.\ U (U \U omH. m momsm.x mwmms.m mmmmm.m o we we 1. as .P: Endom> mm as .ps :Ham.: mamm H :J‘ (7“ r-I L 'W .21“ Edsom> :H AsHomv Hm m A.$w or» onsmmosmv .HH qude . P.» epafisspmae am epsaaapmee ea 0 moasom oesaaspmse am eseaaapaae ea m wofisom essence mm essflflapeae em eeafifiapmes es epaasepeae em epafiflseeae hm eeoaflaeeae as s mofisom -11.. to O\ :1" [‘0‘ N\ rm h— r» m . J \L‘ (‘d :2- pl 0 0U \L C) j. N 61) hpaamsnoz H3N.N: msm.~: :1‘ C\ (3 (If) '00 l\ l‘v I‘- d‘ 41‘ m-.se m-.~s am m e .en H m Ln M C) Lf\ H P“\ N\ CU CU LIN O\ J (.3 C) O m N. N \0 en \0 adsos> sH an me .p: mesm.m Hess.s mosm.s .emmfi.n msam.s mono.m Essow> GH Anaemv Hm m .pm “.5? 0mm essmmosmv .HHH quda mpwHHHpmflm mm opmflaapmwfi ma o seesaw opsaflspmae em memflawpwwc 6H m woesom umHHHpmHU mm mpmHHHPmHU ma 4 moflsmm -32_ memes.fi mmoom.mm mmema.mm mmoom.mm seeme.a wmonm.mm mmomm.ms mmoom.mm wmom:.H mewom.mm mmmam.ms ssmsm.mm wanes.fl mmoem.mm mHHmH.m~ ssmsm.mm s:os:.a maoom.«m )dxfi an esmsm.mm mesm:.H mooom.mm mHan.ms sumem.mm mamas.a meoom.mm mmmma.m :nmnm.mm mmmsa.fl mmoom.mm mmmsa.ms esmsm.mm m EO\u .eoam empeensno >pawsem mo .Ho> coap5H0m depoenaoo do .ps mom so .em msoow.moa momma.maa mmsw.m0H mmmm. .mo smmws.moa mmmms.moa mmsmn.moa omwow.m0H .sHom+.so>m eases» as . m .>H mumda moss.moa moms.mns omms. mos saws.soa oem~.moa meme.moa smms.mos Omen.m0H new a“ .cHom + .Sohm.p3 seamm.sm essmm.sm :Hamm.sm :HHmm.sm sasmw.em easmm.xm :HHmm.sm sflsme.sm Edsos> dd .G0%m .P3 m::w.m~ .o mesm.m~ .m msem.m~ .s “mm do .rs qmwv mesm.ms .o messes .m 2., mmm we .8: oWNV .A meem.ms o mesm.w~ .m msxm.mm .m mam me .E ONE aha .mmwa as an e . . 3-. Fri; . SE sameness co (3 m\ U\ n. P~ r» ( ) LC\ on» own owe ewes msoflpsbnemmo we Hopenz c \ easel densest cepoessoo JBVH. .(Q mO.wNH I ma oo.sma I OH oo.$m I NH ow.dma I m em.sms I as om.rmH I w owima I m 0:.jma I m os.ema I ma 0:.3mfi I m . esaoalmesasom Ue>Hean om. om. om. soapoennoo .0 O m. .4 mossew -14. smom:.H mmmse.fl memes.a I spewsom Hes.~s mm~.~: ~m~.ss I am m w 0N.:NH om.:ma 0mNH .pm ucHHHom eve Hwfigsm Q a; 0mm own one mHSmeHw o m d o m d meanem -15. Interpretation of Data Capital letters in the tabulation indicate the dis- tillation, Shall letters indicate the separate fractions of the distillate, Arabic numerals, unless otherwise stated, indicate the individual samnles of distillate analyzed. In the calculathmicf the average for the densities, those densities of the distillate at each pressure were added and an average made. In the calculation of the average of the R Br con— tent, any unusually high or low value was thrown out, then the accepted results from the individual samples of each distillation were added and an average taken. The final average H Br content was calculated from these averages of each separate distillation. Series B, Table II, was thrown out in this consideration. Discussion The distillation rate was regulated so that 50 to 60 drOps or 2.5 to 3 ml. distilled over per minute. It was found difficult to avoid bumping when a rate of distillation slower than 40 drOps or 2 ml. per minute was attempted. A small window for observation of the quantity of H Br solution present was provided on one side of the dis- tilling flask. The thermometer was read with a magnifier by holding a light back of the flask neck. Estimation of the -16- temperature to .050 could be wade with a high degree of accuracy. Ho variation could be detected in th boiling point afterzuieguilibrium condition had been attained. A very slight vibratory movement of the manometer was noticed but the pressure once regulated remained con- l T stant to within - .2 to .3 mm. of mercury. The calibration of the thernometer was rechecked by rea- ding it in boiling redistilled wa oer at a pres- sure of 760 an. of mercury. It was found necessary to apply a correction of +.2° to the thermometer used at 1300. A constant pressure was easily maintained, but this factor varied less with a low rate of distillation. All weights were reduced to vacuum conditions before cal- culations were made. Summary when investi -ted by precise methods it was found that H Br distillate at 750 mm. pressure boils at 124.20 0, contains L7.77l% H Br and has a density of 1.L8337$ tha H Br distillate at 760 mm. pressure has a boiling point of 124.60, contains L7 .7$5% H Br and. has a censity of l .L7983, and that H Br distillate at 773 mm. pressure boils at 125.000, cont sL7.727p H Br and has a idensity of l. L79€8 . The constant boiling mixtures have a weight normality of: 5.903% at 750 mm. of mercury 5.9063 at 760 mm. of mercury 5.8993 at 770 mu. of mercury -17- a volume normality of: 8.7397 at 750 mm. of mercury 8.7386 at 760 mm. of mercur 5.7286 at 770 mm. of mercur 'y' Y. The composition of H Br distillate at 760 mm. of mercury agrees closely with that reported by Erin: Bibliography 1. Hulett and Bonner - Jou. Am. Chem. 2. Foulk and Hollincsworth Jou.Am.Chem. 3. Ewing and Shadfuck " “ u L. Carriere aid Cerveau - Couptes Rendu 5. Leger " " 6. Bineau - Ann- Chim. Phys. (3) 7, 257 7.’Roscoe - " " " 116, 21¢, and Shadduck 3. Soc. 31, 390 (1909) Soc. L5,1220 (l?23) " 47,1901 (1925) S 177,46 (1923) 115,9u6 (1892) (1860) V151 .LV-r 'I 5111““! ' i I I Illlllullrflll!l.u 1.41v'!|'l' Ill w: l 17/ 5' 7711f? T/UN HFFHHH TUE F ............... 31293 02446 8005