In previous work at the Union College laboratory a method was finally developed which overcame the difficulties of the earlier studies of calcium-hydrogen equilibrium. The results obtained were in good agreement with the best work of other investigators. In the present work, an attempt was made to extend this method to a study of the lithium-hydrogen equilibrium

Walker, Benjamin M.

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Union CollegeUnion | Digital WorksHonors Theses Student Work6-1933The Thermal Dissociation of Lithium HydrideBenjamin M. WalkerUnion College - Schenectady, NYFollow this and additional works at: https://digitalworks.union.edu/thesesPart of the Chemistry CommonsThis Open Access is brought to you for free and open access by the Student Work at Union | Digital Works. It has been accepted for inclusion in HonorsTheses by an authorized administrator of Union | Digital Works. For more information, please contact digitalworks@union.edu.Recommended CitationWalker, Benjamin M., "The Thermal Dissociation of Lithium Hydride" (1933). Honors Theses. 2140.https://digitalworks.union.edu/theses/2140_ . _. r~ DI~SOCIATIOlr 0"1 LI Itl h'YDRI HE T-:ERUAL DI SOCIA IOU 0 LITHI IlYD IDE ---------------------- the ts. presented to the D part nt of Che - 1 try ot Union r.olle e. in parti l fulfill nt ot the require ents tor the ;egree or B chelor or Sci nc 1 Chemistry by Approved by (l) T YU. DICSOCIATIO r 0 LITHIUl~ HYDRIDE Ilf'l'nODTJCTION !Uch work has been done on the study f the bydridee of the alkali met 1 and th lkali arth 11 t l · • Calc.i 1ydride, in particular, ha been the subject or extensive study. The method in gener l is to e sure th e uilibrium preseur of hydro en at definite t perature. In thee uilibri bet een etal, etal hydride, and hydrogen, y ro en ia th only gas.o a con tituent if' the te per ture i n t too high, nd its equilibrium pr sure is mea. ur o~ the reaction constant Kp• In pr viou work at the Union College labora.tory11, ethod was t'inally develop d hich v r e t" diff'icultiea of the .arli r tudiea ot thta calci - hydro en equilibrium. The re ult obt 1ned wer in o d agree ent ith the best ork or other investigators. In the present ork, n att mpt ya made to extend thi etho to a etudy of the lithium- hydroc,.en equilibrium. HISTORICAL rn 1874, P. Rautef uille and L. Troost1 fond that lithium. so ium. an potassium ab orb hydro n ithout changing their metallic app arance as dos palladium. In 1900, c. " tignon2 tound that if lithi ' in n iron bot, is heated to rednes in a str m of hydro en, the metal burn with in de cence formin a hard e of lithium h,ydrid. In 1896, • Guntz3 prepared lithium hydride fro lith1 nitride in str ot hydro e and mixture of lithium bydrid nd carbide by heati lithium in str .m or acetyl ne. Lithium hydri e so prepa~ed is h rd white ass which m lte t 680 C. at hi 1 t mper ture the dis ociation preaeur i 27 • Thee pirica.l compo ition corr spond with LiH. Vapor pressures of lithium wer A. roner4 in 1913 a follow· 630° 7316 165° '799o 867° 900° 1000° C. v. by .05 .60 1.0 1.1 ~.7 5.5 760 • It is to be noted that at te perature of 500-600° the vap r pressure of lithium is very 11. In 1920, I •. 'oera5 t'ound the e t ot to tio or lith1 hy rid (ti, tn2) to be• 1.6 t .~soc 1. In 1923, A. Guntz d • enoit6 determined the he t of f'orm tion of lith1 hydride a 4 .6 Cal. In 1921, • .hrai • ich 17 a id that the re tion of hydro n nd lithium i ry violent an {3 is complet d pidly. The' resul tin eompound is very &table. n he t11'18 the b)"dride1 th parti l remova le or Yr en cause a lar e ri e in tern er ture. 0 t!on of· he bydrid begins beto the tal is tu ed and the ooth reaction 1 prob by due to the gr t solubility f the etal in the hydrid. ~o reference were found tor wor done on the the l dissociation of lithium hydride. re etl:!od u ed in th pre ent ork n developed in tudy or c lcium hydri •• In 192'~ ,..r us and ur heated the lei hydride in ~-rt1 l iron cylinder with the low r end cloaed nd th upper nd open in a quartz tube a.nd m sured the equilibriu pr ssure or hydrog n at rioua t mper turee. he obJect of the iron cylind.r was to protect th qu :rtz tube from ehe ic 1 ction ith the c lciwn hydri e. ome ca.lei did get ut. however, and ther was so blackening of th uartz tube ne r th outh of the iron cylinder. In l9P9, n r nd Stempel9 u d the sa e method us1n n O·en iron tube and h ed by experi ent that th cunt or solid lost out or the equilibr1u s ne ligble in their e prim nt. he next 1 pro~e ent to e mad in this etu y 'f'l8.B the e or e led et l cylind re which were p rme ble to hydro en t tl te per ture ot th experim nt but not to calcium or lei hydride. (4) In work at Union Colle e11, sealed iron cylinders were tried out b ndoned b c uee consi tent result could not be obt ind. In 1929, R my•Cennete10 published the results of his ork in hich he used n iron cylinder with a sheet of ion eld dover one end. !n 1931, liurd and alke:r11published the sulta of th.ir work t Union College in which they u ed a nickel cylind r which w s eal 1th nick 1 plu e pounded in the ends. The result of their work az-e consi tent a.nd in good greement iti1 the res lts of nemy-C nnete10• AUD PROCED iP. , The ppr tue use wa the aam that de cribed by 1rurd d · lk r11• A if.is.gram of th ystem is sho n in ·igure 1. A nickel cylinder b t n lo w prepared with ti htly fitting nick 1 plugs, all turned on a 1th. One plug w.s h mmered tightly into pl ce. The cylinder s then fill d with pur lithi met 1. e lithil BS eer pe cle n n placed in the cylinder, 11 bein done in n atmo pher or hy r en. Thi we don 1 hydro en bottle at the General lectric co. eeearch L bor tor. he other nickel ·lu was then put in pl ee an e nickel eylin r nd plug w re ered ti ht. fore n {5) after fillin o that the ·mount of lithium u was kn • eyl1 der :v-as pl ced n ar the clo d end of a long qua;rt tub a.n.d the tube wa up:ported ho:rizont lly in the electri furnace. The quRrta tube s eeal t the vacuum ys te it d Khotinski C$ment joint. The eyste~ was e ouated nd the cylinder was heate to ~o0-300 c. to drive out the bsorb g e. }Iydrogen could then ha•c be~n 1 t into the ey tem. ~nd 1 would. penetrat th nickel eylind r and re ct wit th 11th1u rormine lithiun hyd !de, b cau e nickel i porou tc hydrog n. if th temp rature is high enou h. All prea u e ure nta ·ere ho n by mercury m nom t r sured ith cathetomete:r which s ccu:r te it in .01 c. Alumel-Ch ml thermocoup e was calibr ted t the ·e d, Alumi um, and Copp r po1.nt to be u ed f'or te peratur ma ur ments. e calibr tion a.gr d accurately ·a ould be deter 1n.d with the manut cturer'e c librn.tion curve, the me ure potenti ls tea.ch of these mpera ture gre ing within .0001 vol. t • The manufacturerts curv was therefore re r wn on ltt.r r ca.le nd u ed s c lib:r tion ourve. el.ct 1c furnac run on 20 volt circuit. Th te perature could be k pt uite conat nt by keeping the current throu 11 the :furn cc cont t. The c rrent w e kept cont nt in spite or lin volt'" e riat!on of a much 40 volt ( 6) FIGURE 1 B c A Thermo junction B Nickel cylinder C Electric furnace D Q,uartz tube Ede Khotinski cement joint F Vacuum manometer G Hydrogen bottle H To pump J Stopcocks FIGURE 2 ~:'.Sj .. ~~ /'. ~ F B Series resistance C Electric furnace D Shunt resistance R UV 872 Ballast tubes J H ( 7) FIGURE 3 @ (a) ~ Li (b) ~ Li @ FIGURE 4 (a) @ ( ( c) -~ Li ( ) by u in one, t· o, or three UV-876 b llaet tubea ii) pr llel oonnect din erie with the circuit. E ch co binatio or tubes pa e• a cont nt current of a definit amount. Av riabl r~ 1 t nee ahunted agrosa the furnace 11 ed any traction of thia onatant current top se through t e furnace. The circuit used is shown in igure 2. RESULTS Thie work nev r progre ed uch beyond th stage or heatin the nickel cylind r to rive out ab orb d gaee, bee~ae it w found to be 1 po aibl to k p the lithium in th ni kel cylinder at temper ,turea of 5oo0c. iour oylinders w re trie • Two of these cylinders had be n prep ed• filled with lithium• and enled y rand a halt before this work was started and wo other after the other had tailed. h firet tw~ cylind r wer beat d to 3oo0c. re prepar d nd after two or three auch h atinga, the temperature was r 1$ed to 50o0c. prepa tory to introducing hydro n into th y tem. e lithiu c thro h the cylinder around the edge or the plugs and aleo through what ppeared to bee 11 oraeka in th n!okel cylinder where the plu eh d been ha er d in. ( 1gure 3). In one of' th other cylinders lithiWI ca e through as it had with th fir t two. In th fourth cylinder. no er ck were round fter thre (9) he tings to il00°c., but the litl•ium till ca,me tln.·ou h a ound th edg a of the plu • 1 e plug in thi cyli d r ere pounded in harder, n1d the cylinder was r 1 ated ut th reau t · the s as be r. It as sue ct .d that the li t:tiium ete.1 at acka the nickel eylin er at the temperature uoed, nd that the troubl e not ith th plu joints ~hich er u ed. A cylinder w therefore fitt d with plu o it. flared ed hie fitte fJuah with the end of ,he nickel cy ind r igur 4 ). The plugs era not ha.mm rd n place s a pre ioualy donu. They wer i Jy tapp d into pl c and t. n ·~- lne closed in n tm ph re of hyd1·og n. Thi de a vary ti ht seal (Se Figur b}. After to hea.ti1gs to 5oo0c, ho ever, lithium oame throug11 the nickel cyli er er the weld had be n de. h al s of th tube wer thinne t at the ld. Tle v or pr sure of lit iu at temper tur o r.oo0c. is 1 e than .05 •4 and is not th r for. excessively hi h. This would aee t sho definitely th t lithium attacke the nickel and that no ul c b ade atron nou h for nickel oylind r to hold lithium. met 1 t te perature of 5oo0c. (10) CO lC'f_,TJSIOl1S It would e that th tne the -1 dieeooiation of i possible of plication t of lithium hydrid. Lith1 at the temperat res u od t nat ont in it. lithi etho use in tudyi leium lydride i study of th di ao 1 tion 1 o aotiv chemic lly t nick 1 cyll1ndox will work it w y thro gh son h col r the nic el oylinder ud con en p rts of the rts tube. It ie po sible that co al cylind could be used in pl oe of nickel eyl ndera in the udy of lithiu hydride. It :LfJ al o quit i, lo ttat the nick 1 cylinder could b u din u·y of b rium 0"" trontiu 1 hyd idf' •. Thie result ill strate the fa.ct that th met 1 cylin r st n t only be e eabl to ydro n nd not to the other oonstitu nte but mu t al o be not att eked by th et l conta'ned. (11) BlBLIOGRAPl (l.) P •.. autef.euille and .L. roost ( 2) C. tignon (31 /:. Gunta Ann. Chim • ..,hys., (5) 2 r. 7,_) (18'74) , -· Coup't.11 R • d., ?Bt SC9 (10? l Compt. P .... nd,., 1:)). 91 ( 1900) r!ompt. {4) A. Kroner U b r die pfdruck l r Alk limetalle; L ipzig• (l 13) Zeit. ano • Che., llSt 179 (1920) - ( 5) K. _Mo rs (6) A. Gtmtz nd •. enoit Ann. Chim., 20, 5-3! (1923) -- (?) • Ephraim and .• ioh 1 HelTetic Chim. Act., 4, 900-24 (1921) (8) Kr u and l•rd J.A.c.s. 5, 2559 (1925) (9) r 8 ner nd ~te1pel Zt • nor; • all em. Ch ., 181, 83 (19 9} ( 10) Re Cennet Compt. en., 189, 579-81 (19~9) (ll) furd nd "a.lk r Thest, n:ion Coll g (1930) J.A.C •• 53, 168 (1931) 

The Thermal Dissociation of Lithium Hydride

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The Thermal Dissociation of Lithium Hydride

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