< \ ../M ’’ i- DETERMINATION OF THE ELECTRODE POTENTIAL OF CHROMIUM By MELVILLE YORK ENYART THESIS FOR THE DEGREE OF BACHELOR OF SCIENCE IN CHEMISTRY COLLEGE OF LIBERAL ARTS AND SCIENCES UNIVERSITY OF ILLINOIS 1921 % ] -h^..'-a^» — ■.U; i rr- rn- n- i f i n ' ' It. iito»* ‘ •HI ■ v-fc^ /'* „ . ' . ” * - , s^miVLi f » ' ' . S .P ^ i >■■■ ' I ■ s ^ ^.'.* » ^' id ■ I ' '^ I -rV-.>.^ fiJ.jV.., •4 . 5 ' - ^ ^ -«w : '«{'] ^tHf1*di^i,ri UVt 3M Yiias Z-.1- Ki' \ ' • . r <1 ^ :;"::/ :.,S‘- : ■** •*^*■'***•'''''31 f-- > < .J 1 d"' - » r-';* 'fh. . iE 3 i*'-.. jt;;v .v';-^-- i;n*S9»' ■ ^ anamjft r TABLE OF CONTENTS Introduction Page 1 Theoretical ” 3 Historical ” 9 Experimental ” 13 Smnmary ” 17 Bibliography ” Iti Acknowledgment ” 19 L I 8T lf>TTB00 ¥0 ** , X cojtcojud&oirf’xji 5 : " #• • •• ...... X-iBOid'O'tOtaiy 'v. , .* ,*'* .V ; 1 ■ vJ^ ^ ■■ -• ■• xL* . ““ ^_f i ' f ' ; .. j . /• -. ♦- *!ii '.« •" JB»^ ■ ’ . ■' , . . • ,* V I . ■ , . ‘ 't f ■ -* ,*•» • ' \^ *•■*■*' .■■■ ‘•• -i V 3 ?\*..i. ; „ .t' .•••..• -t. /: . (I) INTROD UC TION Tlie importance of an accurate knowledge of the potential devel- oped betv/een a metal and an aqueous solution of a salt of that metal becomes apparent at once when a study of the common cells is begun. From such study we come to realize that aside from the purely scien- tific or theoretical standpoint of the question there is a practical side as well. In orderto assure the proper placing of the elements in the electromotive series an accurate determination of the electrode potei. tials is necessary. Many of these have already been accurately deter- mined, some by direct and others by indirect methods; the latter based upon assumptions that may or may not be valid. .Afnong those metals that have not been accurately determined is chromium. It was therefore suggested to the author that such a deter- mination v/ould prove of value, as mentioned above, both from a pure science and practical viewpoint. With these things in mind the author set out to make such a determination, if it were possible. In order that sufficient experience to handle the admittedly more complex problem of determining the potential of chromium be obtained, it was decided to check up certain values as obtained I by recent workers upon zinc. The results thus obtained were not Just what it was hoped they might be although the apparatus as used by Mr. David Schlesinger and the author did not have some of the refinements that the other 'workers had. That is, to say, this apparatus lacked for one thing a thermostatic control of temperature. This was in a ce rtain measure unfair to the previous work that had been done, but it was desired Digitized by the Internet Archive in 2016 https://archive.org/details/determinationofeOOenya ( 2 ) to obtein some data that might be used in the solution of a problem connected with a laboratory course in which the refinements of ther- mostatic control could not be used to advantage. After the suggestioi in regard to the use of finely divided zinc prepared electrolyticall; had been carried out, the attention of the author was again turned toward the real problem, that is the determination of the specific electrode potential of chromium. ' Vj,' "if '''''^ I ■ I ■"ph.gF^^ rT.-^-iaft- ,■ h;; = ' fj "ti ab t&kiciii exftf xtt- l^t*u IrTi-iii io e^£ttoi^ai'5:!>isax3Ut ioiil.* ^gix/oo d^riv. Jbt>jo©. ».• oaii b&feJtvib ^laxa^ lt» ©eu »if{^ nl i ^ -T . ' f ' Spi«^M63$y^ *X©if^tA . 9 j j^ t tiii’VhJii Oif £kii>0S/ 6(5 ^0£l £kXji09 XOT^AO©' 0 XJ'4^0v*S ►• “ • ■ • ■ * 1-fCF -GcnUf 6jflfr ^ou'.-uA &4o ainol dviJ owo:iJosI / arLt lo ttinuoB ^o' ^ 9^^Io*iq X»oXti9iU>~o*xJ^o© 1» Sr 9dw xbis^e « bstIovaJ. floi^aeup 'i^vkcM w - ■ - ^ «d llmie Bm itoiifw l^oid^s^oiaul^ stAJ- '1 . '‘^fesiarcio'sq I^oJE«^c^ garrtoirxt oaod^ ^54 ■ . - V , • V i;*'- 'A 11 bae eu to of b 1 iisd ICalncd noassKMfr e ■ -^' ■ . ; ft ■ , ■ , ■ ^ «' -.f' ■ , ■ .f iiAAirJv rf«'t*iF#: mif/ft -u-«A cj vrft /ftrrdii^ , i-.. flw aJ.ii a*xA &*ia a-tsa^tOavea ailao Ixx'crxot lATaS^ ai £r4i£:^ bait aV .dle^ioT /'rf*: V.; * ■ ^ •' Uf" . jT f !-•->■ '■■■ ■ I- / a \:u abcntroej^ Oai:>> b (.aXf^o 5^ajKi*xci) /I j>AxiJ Xiao B.aoi«'3iii:>xMo* . .. .... ... -f . .’Jt -*..«,. . •Jr'. lo aottwX-oe 4 ii otoicroaX'’ 4{ c' )\oJr4lXifa bnis tai «vaiT snionfq ^0 liaartdt il Xti:r no'ii ^ I£X» aQlj7^BaX' Tti ■ ' t l.aoixJooIa, rxaxt 0 ^' njso ?I< «dr 'tdXoi't^oalA to qji as.? ctfiw r'o^ooanoo otb «ad«oooaq;^;iw»Xtr^‘' ' ■' ,-..^ i’?i5- ■ . » “ "fiil — ■ taraasiflP .as^‘ia4o to <*o 4^Xw laeaeooi^ aoX«JBTi;5ol6 ffi. etf -tax ’tifcf jbo^At^qae ad oro attOitoA' ' ow^ •ijwlf '•: ■ , ■■' . . "f '■ *•■ V ♦. X *iXoo A a.TW^ ow tiodJoiw eco Xa^qaA^iiivia., ai aaato't® inW to x^jWnAvp » o©vIo?£ji,r»a; oiiT to' eo.+aJ#' iBait J^ OiXii^qiqi ■’ • ' - X, ' -X’- • 7 , '-- .;' " X«oiaiOdo edJ toto .eaioia^rsq oii^r ,30ij‘4'itnftoxw>o ©4«i- ,s^'x;/^^O0»o/,y4j ^ - iBSCj ii&ilJ £>A.t04 ad' ot •! dX .©o^Xq 341 X 4 ^ I.U hjgjff Wi ,. *'* " - ■' yj ' .fra i»''i. 1 HB ’ Jfi^gyi -uy::i i gviit J » »t. ■--* ^ . 1 ' «T ( 4 ) force or tendency toward cJiemical reaction in a cell is measured by the voltage or electromotive force that is developed. The work done per unit quantity of electricity flowing througn the cell may be given as a definition of this quantity. This then, shows how closely related are the transformations of energy accompanying a chemical reaction and the electromo ’.ive force it is capable of producing, if carried out in a cell, and that this force may be regarded as a measure to a certain extent of the energy change. The electromotive force of a cell is made up of the sum of the forces produced at the junctions of dissimilar substances. Thus the electromotive forceof tne Daniell cell is the algebraic sum of the force from the zinc to tne zinc sulfate, that from the zinc sulfate solution to ihe copper sulfate solution, and that from the copper sulfate solution to the copper. The electromotive force produced at the junction of the two solutions is known as the liquid potential and thax produced at the electrodes as tne electrode potential . While certain attempts at determinant ion of absolute values of electrode potentials have been made, such as by the use of the dropping electrode method and the capillary electrometer, these have not been very successful. That is, to say, the values so far obtained are not as good as the comparative values that are always meant unless otherwise specified. Measurements made by the use of ordinary half cells as a basis of reference are more easily made, and from such measurements our data relative to the electrode potentials have been compiled. There are several standard reference electrodes in use and several scales are employed but we shall make use of the normal hydrogen electrode in all our considerations in which the potential ... *r> -^"1 . ' ' 'V *-'■,' i - (/•) -- I 6 C) *i i'it nc iSdy.'rt . i>(.^::o.r©vMb eono^ PTlrjiiaij QsIe ’ic ■ tvfi-IoV' adj 4 I t 4 a . •^f*--. lisc &/ 1 J aJ^l>oXl ’cJiri-tJo^rl'? *lo i iay ‘jciwi <»n^* t- 10 lo nci .' 4 e«, isr^i - ‘•i«-i vX*:;- red 6 «?£fs, “l.'^^- L V ^L.i-j'j rs. it? vUL 'ti Xcjbo*i.; ©Xc ‘ ?i i?l aO*ic' to 5 no’- 0 r.t-, ^ «:*•;- n ea .■''. ro i- :.<:i iih ei •" iC-^. r: V> ^r.* I, .i W :t . vv-*;w : .r'C*'- , J&C.S .r j,; . il/I j a liC' : ‘ '- • T X* cteO"' ■• . tj .*. ..j, .:w tfti:' et H^jt'’Xisi ■•V - ' .— f-*- ri’ .•■ X e.' tiroXs-;;?^. - . •■'J.f 'to .■ • fi.'f/.-n'!; nt, «Xiei% -'"' ‘ - ‘} =r 5:1' ‘ .V fenoni 'rt n* ^ .... — - ■' ■■■ . . T Ip 1’ f;t.,Io9r?s io 4 . .t« 1 i . » s S£!.‘ tr- 9iiJ Y.*? ftis .i99$3Lr- •‘rr ,*>*^t-.;r;-.'’ .u i _.X :.^^,ro.u ©pov ’oa^'; ^-^Xg^cTij .' ■ • Aiibictt 1 0 -r.-j'' .’•c so„;ie -7 . ."oio frj .* v\»j-».- I aj ’.•ic , i^u> 'dOuX^T ov.t : i^:‘cn »*t ■' ^,v'. ' , iu eoi?. flit? Abyftu ej'cesa^'iiie .: :"lfjoqa « •. -vo*^ 'i a <; . - yXX a/jo v'tOuI arsjs ©arti"' ■■ ' -' to, -‘3c « * *?rvv< 5 -.^4 1 ;ii: iiwd &ii3ic rr©r oc abc^.j-'i.-l P c? 'PTiCjeie't st-.i.i) tuo ^'. ; uT ’ :?>o Wii; ai -s:,'0T*p©^9 one'isi&'i ‘ vf>T :‘*ti& f - r..::.:- ;-. ^ylc^r Clrt-K''**' -.hv .'*jd '^'.*' s . ;.oi.c. btir. (5) developed between a platinum electrode saturated with hydrogen gas under a pressure of one atmosphere dipping into a solution containing hydrogen ion at a concentration of one formula weight per liter is placed equal to zero . From a consideration of the change in state which a cell under- goes there is developed the expression for the free energy decrease experienced in the process _ = N A ^ in which c, and c^are tne initial and final concentrations, k is the gas constant, and T is the absolute temperature, while the log term is to the base £. With the aid of the other expression for the free energy decrease we are able to arrive at an expression v/hereby the change in the elec tromotive force developed by a given change can be calculatedj- y^=r A/FiT A Si- Maying use of this relation for the changS in free energy upon dilu- tion, assuming that the solution is completely ionized and follows precisely the gas laws, Nemst arrived at the well known and important formula which goes by his name namely: - ~?r where E is the potential difference for the ionic concentration C; E(,is the electrode potential in the case where C„has the value unity, K is the gas constant with a value of 6.38 Joules per degree; n is the valence of the ion; js is the farady or 96,o00 coulombs. This gives th~n a method of determining the electrode potential lfi^,if we know the other members of the equation. Due to the very nature of some of tne elements it is quite easily ■ 5 a s ■m ■ f* ' '•- ' „ , ‘ ' • B.. '". ■ . - , ;i;.- , _ r^^ottxd iiflv bau^jnif^Jia ii^jbcri^^takaie aa/nJ^^jC^ jb nesw^stf fa856^TB^j I ^jT/itl^jsbo r:oi^»Xoi^ A sfriq fi ' ■ »; rr.sibrjj llm> Ji.tipid^ .QS I *'.lf [^ Aoo«U ni tir^mdxi lo. , •' mont ' >^'3 ’■ -») ■ ^ ^ P^' sf^yoebr oijUf to-1; a;>X«#&rx^JK« 'Mi? jieq<3le.T»Jb »x ’©iMj ^Vr m ■ ' rtsn^:^- ?cl m4 9lid^ Q^vihB4s pilS 9l 7 iiic «^ao^oadt> i • ' ^ - i.. '; - A ' W I 9r«^ SH^ ■‘Oi aot««8TJ3*5 5'ft90£U>& XaAil hita XaXif^ittX Bait ©*tJBj,qv£iiia ;' IT"’ ■‘WW f ' ■^V\1S. »•-* - raoftdiaei^ ^ 1 -e i.6^ ©Cl rtX 9iL? iiote«&i(XX« oa it« ©Tl'in* ©X<^ j '■*■ f=\ ^4 A 3^^^A ^c::^ jfi A ^ .'"'A'. IS •'- •'-rXXft jotiu -^©{wf ©iJift' jfli i^eU ic*t cotXiilGa ©bx* BiyoXXo^ i>c« l>e:5,Xa&i »i iJOifTifitf®' M? ifxrii?- roJl£svijlii» K' i •■ ' .1' Tt It ^ A-.-J* ■ /vV J)a-. miiiM tls^v pdJ t£^p9rlrvia 1 bw-’K | ^tvieiWifi ea^. »X^f -Strf 6®^^ liBjtriw aXmowo"* ^ 0£UT' ■-;?^ .^, ’•' '?s*t BwX‘i'v enBilw ©»«t> 'Bifl nX ^ • ■'*’*?' _ij si . a ;B6*xsai> 'i&q S&.6 lo atfXAy- # £tl.£w sr^Tij? BirfT .cdJBaixrb.B O0o,Dlaoi ■5' 3 t*.' T ■ j g 9!L?jja B Hj;jK:;ti - . >• t. ( 6 ) seen that the use of a simple aqueous solution of a salt of the el- ement whose electrode potential is to be measured combined with an electrode of this material is out of the question. Some of the metals exhibit such properties as passivity that quite materially affect an accurate determination of potentials o y such a method. There have been as a result of these difficulties some very ingenious devices and methods brought forth for getting around them. It may be well at this time to pay some attention to a few of these that we may have before us the possi Dili ties in the way of methods that have been tried. Aluminum, as is well known, exhibits the tendency toward passivity. In attempting to get a value for the electrode potential of this 2 metal Kahlenburg found th£t the effect of a solution of sodium hydroxide was the same as amalgamation of the electrode. That is, to say, that in so far as the caustic solution acts as a solvent for the oxide of the metal and thereby removes the tendency toward passivity the mercury is thought to do likewise. The use of amalgams we find has been fairly general even in the work with non-aqueous solutions. The potential developed by lithium was determined by Noyes and 3 Keyes by the use of the systems Li/LiCl I propylamine/Li -Hg( 0.03b yh) cind Li-Hg LiOH/LiCl/KCl/nlCCl nHgCl . In ^sing such a dilute amalgam the action of the water upon the lithium was practically nil while in the propylamine there was no action. Then upon the assumption that the difference irypotential be tween the lithium and the lithium amalgam in propylamine is the same as would be given by the two in an aqueous solution they were able to get a value for the electrode potential of lithium. Similar methods have been used for other very reactive metals . It is interesting to note that the potential of zinc, copper, a. ■ ’^tTM vx \iu' .-te .,. ,'.i ::t .■'^•■..a:-. • ■ :^^v> _ . 5:^’^ >lz) d*Ifla » '1c0 n>iliifo^/«uovilf/5iS sjfqjiiitj. ^ eil^ ,*i©.!yd %'. ^ 7 - ^ ^ - '■ . . : fift >*c 0it I- LMiiiti^'f oq 6J&ote^ 6X® <^«odif ^ix^c "fe ,aci&^^^p fo ijjv al -XcJ?ts^4wi eid^ ^o' ai)ji©« ficto*«©S4v^^' ' . '■’* ' ^ - *. • . 'J^j ©« aisdJ >p' ti'pl ja of Xiid^Sa^Sk 3£^* ’^*5 eyiif MjAdJ* ©jboiilj^^ c“t Oil5 aiolsd ^♦4 "'^t* ’ • 'v 4 ■«»•?■ , •■ ,f .*>‘ ' ^0VX«»4>(i Xi>f«r fei oa,<^/4Xu)bA\' eevo.ns'f hxia edtf tc tttixo jriidT ioJbpt^o^X® ©41 to ibJli*eAw^ ■^- ■* ■* ^ * ^ ■ ■*'®^ J '■ tpt ^JuKv^Xo^ fl ifS.%ioA norl^loa as Iifiit s® t?3i6sX«ff»a'* t j 0UU itH*^ . ©HX»#a4iX.>'6jb 14:1^^^041 •jfi^'^Tao'ifiw Ul^ .©aoXlalca &iycrt»4j^ji~a:oii rfi 2a Xtovi odl vnX iXtnr© '^XiiAl$' - i 'aXxtifcf 1x0 fi.iMi totrii^iX sril aoq[i/ ta .apil^ ihdfi aer^o^ .^tf £'i>n^*i©l»4 o-»^ aa/t4lXX 2)^oX^oA 1 o£C . 0 )^Hr X J\an life X^^oiq I 1 DiJ> t J arti to; 6 mmX-- V. ffiA^X^aa. aw^-oXidt^ JE .ff J . lOaHn irZaN^XaXXXOiJX^Oiij V* vpcir ctp4'0 ts^dj wo &c «ovr ®i»ifjf ./ p ^T >■ *J ■JtliJi? X £. aitf bha iDtrx4lXX t4?44i»4>»'ia(X XaXlrtalo^X .:■ .r r ^ ,:.:vj: iw r4 b«'0 pftl riayXa bil'«rt|i oa >dJ ©X SaX®>«'iWw 7^*< xAxlq9ic<[ abo'ilceXa od^ tot axjXe^ « l©a opioids ^dt ao Xtev tadlc tot baox; aood ' .obodioar ,-t0iXit4€! .a^’tjfcriX '■ ' '"’ ’ ' > »' ■ . ' r* ,.(' L*^‘ U’ ..• v? y vK.. - >*ir ^ ' ^i' ^ar 5 eWi^ 6 »i« Jii a ^ . , . ■* ■ J'M B% i._ ■ *7‘ ■ - . . f: ■ •, !>» ■ t, ^ -. < f - Xi*'^ t^ii^i^irioa TOl !> 4 fri^®crfiri) 6 'iftw h^juIav ' ' ' ^ ^ ^ -w ^:i-;,': 'f- - - ■ ? > . ^A- . lasrio/1 Miiif Jb^A lAinoa #»r tjrjic " ’ "" ^‘"' ^‘^^* "'t ’ 5 ' ' - ioW<^abit»rtOi ob^o £alJlToW - ii Xi lo aflj iJWiif / *5rtatfi^f>o5!,&jy£*v »6aa« Arf; eSSki «Is^tii« XIb >ic 1 *i®Hyj^r-i3t!|(‘ Iotf<>0 i, ’ ■ ■ , '-:-i . I . . f;? fc©nx^ci$^b i>iVi ‘iMiiitJ^.A a« *it>JcX i/|£*.< iyOiitiX tc&t ^eii'i9,• :i6XtiiC[^ dJEJl borf^^m gjfciiT . *#i:oi^'i-£o» •mXAn at ?.*'i5j axu, tilsJiw bn^i niu to viofir mb2 iU f\piidlld ihovci ^JSiss^do eaa Ib’xhiu^o A »ticiS 3 'yxj £r* aa»io 7 ma m^tS hjniii^ I i'J acXJ«ffX^ 70 irai ->ca& c;^ xm£ W 7 oitri«iit 6 *a ' I ■ ® ' . ■ . ■ V ^ n% ^ • ii» if’xv^'%97 lx 9it7 t 6 x^T-'jg X*i; M a 'bjb /it## !tu ftoiX^tfAiir.oe eicd ai J*.>4^X© aa^ir iiitJW »yoXva*i* f* itt* 4 > oujtiRO’jjdtt *T 4 |flf 6 auot nwb oaxf *: •'n < ■ d^^ytaa bS ^jaiJ'toooa ^C *it> CIO ,at»?£Kr5 se'tly aao ai. 9 ^i to 9 ^aS 4 IS oMii ails' .ft^yioiaqartt' AJi ^ba;j s^ttoT^tQ^X^ 3i;:^jA saT , cc>‘it to acAJa oviaaaq arf^i stsim Aoi» a4i^ W '■* 4 S oa;fVjsia^ -^Iqnii^o^ ttys^qo .tio*ii iq* ai^^i » -aoQ aa,: oj 'saXsJsaloia ci bnottxi} ^s to 3 ^a:? 5 *tCiiy Hix 7 6 eabqx& ai-il 'doxiiw os esciioi./o'^txts iaa' iiydiJ /i> 1 • * '■•«'. . ;-> *i . .i • ,t '. w : .. . i «!■ :^xxs ; ~x T • 9 XV eivt’-. ' x^atxLj ae s i ■ *£). ( 8 ) chromium appears to be an alio tropic element. Chromium exists in three different states wnich are known as active, passive and inter- mediate. In each of these it shows a different chemical affinity Eind has a different chemical behavior. The selection of proper working conditions necessitated then, as mentioned above, an historical treatment of the element. C ( 4 .‘i •i Lh't i.. ■».* '* 1 .. '*r ‘li* ^ ^ ^ 'V » ' ‘ - sj * ’» • i. ■ r;iv' . . $ ' ;:adni»*^ifc i- vi^wri* ii:. ■ .T . • ■ .. ■ ,. ;-■ .Vi •'iv' r . ’i. LT, '• X J Xi'Jlk/C ' f: ci’iO» ...M.T 1o vi:T'v V;./. t(* .. .. f i.:i y>h ♦ovocla.vfia* ’ (9) HISTORICAL n Hittorf found in investigating the electrochemical behavior of chromium that in dilute halogen acids or sulfuric acid, chromium dissolves on tne application of heat with the formation of cnromous compounds. Nitric, chloric, chromic, phosphoric, citric, tartaric, formic, and acetic acids, caustic potash and soda have, however, no action either hot or cold. In its electrical properties it is found to be electronegative, not only to zinc, but also to cadmium, iron, nickel, copper, mercury, and silver, and is inactive in solutions or these metals except in that it reduces mercuric or cupric to mercurous or cuprous salts. When employed as anode in solutions in which it is indifferent, it was found to become covered with a yellow film of chromic acid, and the loss of weight of the anode was found to correspond with the production of sexavalent chromium ions; this occurs even in solutions of hydrogen chloride in which chromium ordinarily dissolves with the formation of chromous salts. This he supposes to be due either to the decomposition of the water by the anion and subsequent formation of chromic acid from the lib'^e rated oxygen, or to the formation of a compound of sexavalent chro:nium with the anion and the decomposition of this compound by water; no such compound however is known to exist. In solutions of potassium thiocyanate or of an iodide, the chromium anode exper- iences no loss. A chain ojf the type Cr/KCl/NaNO /AgNO /Ag gave no electromotive force at 5°, and the same result was obtained when a dilute acid was substituted for the KCl solution. When the acid employed, however, was sufficiently strong to cause the chromium to dissolve and the evolution of hydrogen, an electro motive force of 1.056 volts was obtained. When the metal was used for the electrol- ‘^43 r ^ 'I »' « t MMmSJS. Jr F( r. 'roi^x:& 4 ^c iil bixinj>. S'!! ;*> ii-, / Id flOi^exnnal to floiiiftilftq# XUf ,‘^>7S^;;;a xf^iiTpi^ ,6bi©iS >* a '.' -’^ ^ *» ?■ ' ! ,»i /i >»iiia«^ a^ij^5«ri» »#l rtl .4X00 ID v-8d iojlifJto noi#lt ,' : » -..f ' ..r.f • (4 . “ ^dtAtndtf Ol-U^r^A ’ro eJj J:i>A^^oloJ i^Ulih aJ .f ^ j 4 ' '*v>^ ^ V-,*., - ( ^ . ...‘ . ^-’' •^.'•/^ ♦.■ •-'•'■•-■ . . ' *' ■ ^ ^ ' 'T " 0Yl7^£U^X'**%-4‘ is^>" ,^irC’T0A iS^ih •’r.' s. -y ... • ' r. *i.c ji. iT-i 4 if»w!LP .oiOJ'iam , • ^ blSr\^viX^% ' . H^ilSS ^;(||kvJf.1T^ *J9 0^^^ prU o»t- ii«ir 1 1 e«!5*i€*Yt^4?f nc>JM-aiVA0ifpl^M,''--^ ' _ ’ ,. _;■' *■ . .j V "*.■■ , teli'' .'•#• »1 ,..‘r ^ ^C 3 tr/« e.sol eii.t l>ja£ ,fcipa ‘Olajc^tdo lo *irf :t fwi f cro^vcto. *Kj>t .« .».• . . r./ ^ -I j. -. • ... ‘ t\ - ^ ?nsj;^«u[©e ,^=i*xt>opjO aLx?’ j® ‘ ^0 aaviosaii) ‘tXi'^caitrtc dold»4:Pr-U^, j ‘ - - '*' • * ^ f ■?iiJ *ID iVtfio ■ • ■* - V ‘ ■S -: - ’ -noffso » 6 <^-.^£ri» 4 . 9a«i„ oVj rt»5^ 1 - , . ■ • ., .,. ir h oifS'i/ uBtijijsstcx> eeH ad^visita ao^oi^ aY^ojtscT4oa!F»^ ^ r,- '^ • ® . - ,^ __ ■ 'V. ' ' ^»v *^^■'^ ■ ■‘^^c ' ^ Ort !8C:i9J0!xdt>, e.A oewjao o^‘ SpW^Je bjs^ *ic pospY eyiioui- P'Cj«f«,Xa aripl^^ -* L'. ."^ ,*.j '^■ r ia, Xa ^S4^:. a/i? Auzflr . . l>aaiiBJK^o^ h.im > a-q!g ‘t . 1 . IJjJ jPI «^IoT:acO. *1 ( 10 ) ysis of melted KCl or ZnCl , totally different results were obtained, and the loss of weight of the anode proved bivalent chromium ions were produced, and similar results were found in solutions at lOO^of the halogen acids, of potassium chloridf, ammonium chloride, and in sol- utions of zinc and magnesium chlorides at higher temperatures. In considering the inactivity of chromium he does notthink the theory of the oxide film as applied to iron applies to the case of a chromium. In a second paper he suggests this idea. Owing to the existence of the different classes of chromium compounds the metal may exhibit any potential between the two extreme values;the highest value corresponds with the active state in which chromium gives rise to the lower compounds. This active state is assumed when the metal is placed in sulfuric, oxalic, hydrofluosilicic, or the halogen acids at temperatures which are lower the more concentrated the acid; it is also active In fused halogen salts or their boiling solutions. The metal becomes inactive when immersed in solutions containing free chlorine or bromine, or in strong oxidizing agents. The limiting values, however, last but a short time after removal from the liquids, the metal speedily assuming an intermediate state; the most stable active state is that produced oy fused halogen salt. The activity is also lowered when the metal serves as an anode for a current produced either externally or internally, and with sufficient ly strong currents chromic acid is produced, either by decomposition of water by anion and subsequent union of the metal and oxygen, or by the intermediate formation of a compound or the anion and chromium, When the metal is used as a cathode it rapidly assumes the active state. A. Fisher in undertaking the study of the electrochemistry of TA- I 'V ii ^ 4 . • •, 10 . 1 .; -; c » iW ( . be^i '..• d-. wHst-^v . ^iC j;:^irr-r lo \ or.v L'l. . 5. »'t S' vr b-' ly«rst u iiu .^..esalrv'.c rt * i < sx>j •■ '. V* ^;>v •'<“•■ ' K .'.. i . i . :; -'. Tio ] .. ■ijis; | ‘■^oi’i'.L.-:- .•.riT ^• ■ .;i,: la.' - t ' ’ V ? oi ) oxi "'TO 7 ' ;..'"■ ., * ..- jii **’ * f-.i *■» ■ ; ^ ' * • '^' -4*^^ . . > L w c . .•«.' ixT c?riqi4-tt PJ o *. * !; ii - . . I .. i ',. ‘•’‘ ^ ^‘C 'j .^ ,; L , . k'o. C* C » ; .•1 ’ IT - Vi :;; 4 ’^ jit :., • .V ■ . .1 V :v -: r:j C 9 dyf *. ■ .w •. ^ I;. ab'^.u fLi: Yo v*jc"^'rf f <’* .;. 'i:o>!-2 .:i2Tu0^ite i . |i ■ i ^ KhsLi , :? 1 c a , . • -.. » .■• •: y ' iciJ 7,/ . ■ : i a JLij^a 7 - . c: ju ;/ rw , •'. tl 4 S > 0 ^'.-rn " /irs 1 *. ^ L ipJI ' Oi-fJ L V ;•: ti • . ' ' ■ . L ' i\^h ' rit'iOd *':.; t ‘ Li . / .' •!* '' oX , .;.< 4 ; I .t f ' v ;, 0 : ’ P - O’. f/?] M 'i" I ■■* s ' jr.-ft 9 Xi oe.tf J & ta'i .."wWH . 1 . .. . . .1'-: ^ ' ’ll? '. . ' * ..‘ •.rl. ..rLciJe^t^A l,Ci> ::o.. or* i»j eviJo .;, .> O V T .T :£- s <; T » cj . 033 : K ^ iyj ^ r <. j , . tj ^ »i t :* sX r.i Tit 7 i If . nHo .. ‘ • Ti »;!. i j , - . '' ":.o □ ;1 i. ',• , r ' ; r .. u : ' - : - . .. fcv . ; . ; .1 ba 9 nc xna .c ' ii ’o .V ,. T ; 'i j * tiite.\ri . ,;;c > ,•* i oLgAYco ii *r. ir^atr si J o**t/ *tt; Y '..i; 7 .'■ •%. '■• ■ •sfm W -: l -» _• L ik. ( 11 ) the chromium group or sixth group metals says that the problem is complex b'^ecause of three main reasons. These are: (1) The diffi- culty in preparing aqueous solutions of definite metal content; (2) The tendency to show passivity; (3) The preparation of absolute- ly pure metal of uniform size and shape. Fisher's paper treats only tungsten and uranium. He used the method used by Roderburg making use the relation E, P, (water) — E.P. (alcohol) = Constant. He found that solutions of WClj^in ethyl alcohol showed the least passivity and alcoholysis was minimized by suitable dilution and maintainance at low temperatures (2°). The element W / W ClQ^in ethyl alcohol and LiCl was prepared and compared with Cu / CuCl^^ in ethyl alcohol and LiCl which in tuna was compared with Hg / HgClg. in ethyl alcohol and LiCl, referred to the standard calomel electrode on the absolute scale (-0.5o volt). CuCl^ was selected because of its similarity to tungsten inregard to solubility and its nearness in the voltage series. By determining the conductivity in the alcohol solutions so as to arrive at the value of oC ,tne electrode potential in alcohol gave the value for tungsten as 0.660. For copper, E P, ^ — E P. = O.O'?! volt. From these values (water) (alcohol) Fisher concludes that for tungsten, E P, 0.680 — 0.0?1 or (water ) 0.b09 volts referred to Hg r 0 . In undertaking the study of the electrode potential of chromium the literature on the electrolytic preparation of the pure metal was also reviewed. By using a solution of 100 parts water to 25 parts CrCl^ and working at a temperature of 88® and a current density of 4.3 -5.3 amperes per square decimeter a good deposit of the metal was .c fr**- r> • jT!- '• ’ ■• ■ «./■ ,1-v- .=i»-^.- «.-^t «'■ I . r ^ j] ;^. i exl» oTT«« sX^Sin qiuo’i^ tc iiu/Xajo*^* d ] - „ . . , . ‘ ;.1 (t )‘ jVs/» 'ii3Lijo«««©»j flijtfti ooiili lo ©ewjOfiTcf xoXqado^ -* ^ . •' rv . •jai : I'rpitMsiQo Si^ ifUy^Jb 3cd 4<>iX7.'^g©7q ©ilT l^V ;t!;XXvio8j6q ©off© Ov \;&£s 4 c./t#X^ 94J!P {S)(" /J .0^40 f>AJCt ^uio criolXfu; Ito r.i> ' ‘aijnj Stus*4/ eS .ay/i ala'll; fcxifi aaS^^^Otjj ztnc X , h'v ' ■*> •' IS ’. \ ©ilX' ©lit; j . •a-jXjfUTOp^- :i»fiooi 4 i) '{la? '( i w-^^X &2t^ ia4o5.io io ftuold^irXoA VflJtlX • r-- Ihbr ivitfto «j«K mlexlodooXA luta pi^ iO W \ Vf ’^2% •{‘^^ ) woi'Xat ^0|tiirtiJ^j|IXiSiR ■ - ' • ■ -li L'ii ' ^.' ;■" • ■■; fe:,' jjiOjrO \ irD Af.’' f«qicqti‘ i>rrz iio« iOxJ i»fac foil<^oii' "V f -X j4' ? 1 -4' -.♦sd^ a„y? .J>#ir. IXcr6 = « S V .10 '^'^•0- --oea.o vt.. «r.2 66bi3XoaWTi9irm /'itl I4t. . O r oX. i6drXoy,,S»Q6,Cii4 . , ’ ■ >' ^ i# ** ’ - |^■i4I^6'^ :.^, «ii4 to oitJ. ^icU44l'xOJ>aii^ uj7om eatr :jo noi^'pAtisq^) 6i?x-^W0t*Xe -.©4? ao ■' J ■ t»cui ; sn 1 ^ . tOl '- i-Tc Iii' ‘’•.W ' '5(5. 60f . . laal-: a bt*. A ll« - -i# O j» r^J * ioXri’tr J :i/Q »-u4ic> cfj Cl I x&» b.^ i- - .'W'^d *. » ^•' k l>i’X&XiSc' eaoa c'iiio *1<5 •' ^ " i;' ✓ t Co -ii 'C-! vw MU* •J ~ ^ / .*■ • w- - w 4 /• *. i* • »' OCO'SJI '’.v- /«--». •■* »r;L?ri.i) i a ■» t v»cf j!T '•-J , / /•< , , ' ,.^ « Ci * ‘- iL L'-' t . 1 ’W •■ fi > ^ :. Of:.^ '»d*«sr ^ »r r Q^" (13) EXPERIMENTAL In the laboratory of electrochemistry at Illinois zinc that has recently been amalgamated has been used in experiments on the electrode potentials of metals. The results obtained have varied so much that there was the desire to improve upon the method. Finely divided zinc as suggested by Horsch'was then tried. The metal was produced by rapid electrolysis of tne zinc chloride solu- tion in which a rod of pure zinc served as an anode and a platinum wire in the form of a spiral as the cathode. The current density v/as not kept absolutely constant, that is, it varied somewhat with successive preparations. According to Horsch this has no apparent effect except in the ease of washing the metal. The spongy metal so obtained was kept covered witjr a solution of zinc chloride at the concentration in which the E.M.P. was to be measured. Upon standing for some time a small amount of the zinc reacted with the T/ater to form the hydroxide. This hydrolysis did not effect the utility of the zinc for after washing with dilute hydrochloric acid and then v/ith water, the metal could be used as before. The zinc chloride solution was prepared by dissolving C.P.zinc chloride in pure water. Hydrolysis occured to some extent and the hydroxide was removed by filtration. The normality of the solution was determined b”^y Volhard’s method for chlorides. The Ag-AgCl electrode was prepared by first plating a platinum gauze 7/ith silver from a cyanide of silver solution and then the silver chloride fomed as a black deposit by using the silver as an anode in a dilute solution of sodium chloride to which a small amount of HCl had been added. This electrodi w^s standardized against hydrogen in O.Ol normal HCl and found to have a voltage of 0.4653 ffics. ^ I ~ ' ^ ■ t • — * ~i**J lYol^?orti5fc^^^ .snxft.q.o c«w ~ju;v - btffi xateaxa, Pi iifrTXjnrto I 9/sJ Sil'.xJiX'vaio/i Sri? -isoiiirtilxi \£tf £«7oise^, e!w 1 If • ’• ‘ * ^ li-i -• Ss.- IL, . ^;.. _ . . . _ V ***^- TV: . 9hb.l^o^i::j^xoX (R » ii'iAUoV rjnax^ „ '■ . ' ' '■' /^ . It -' ' ' :s >.W?S' iO£i iXjfcOr r-.; . vV '» i Axrsqa^q'' 'e6:oY^ oeA#^ . ■ ' '.i-,T’. , . ^' ■ --: -,ji # I' Ma /pc-ixxao^ iWlxfe to TaYli©^-^ ’ ' „ ** . •• ' ,. **'■' ''■■ ’**S1. ■‘W _ rwj RA !pjvlip 6^ 5icUa-i.v xl»oq§6 ft lix:iollf3^av^ l‘o noljjxlb© eXallb j “ . ' ■^■' ^ 4" Y», , T > '■'*'■ ■ ■■*' ^' .y . 'f '■ ■ vT jax 9 )** t^SAl^CoY ,®, ©y^7 ox 6|iv _.A- ., /-v, ...'^ .. ■- t^L , . 1 . - . ... "' '^ (14) volts, this reading being the average value obtained from a number. The complete cell was then set up as shown on the following page. It consisted of the chain Zn/ZnClg/ AgCl/Ag . A table of E.M.F. readings is given below and represents six cells as numbered (1) (2) (3) Cell Number (4) (5) (6) 1 .1688 1.1580 1.1600 1.1605 1.1649 1.1580 1.1689 1.1550 1.1610 1.1604 1 .1647 1 .1578 1.1680 1 .1850 1.1610 1 .160? 1.1658 1 .1588 These results show. in a i measure , the very thing that it was desired to correct in the method as used in the class work. While only the values for 0.01 molal solution are given, the author is of the opinion that the data are enough to prove the uselessness of trying to use this as a class experiment in this form. Experimental (Con’t) Work Done Upon Chromium in the Laboratory . IX It was hoped that in a manner similar to that used by A.Pisher a salt of chromium might be prepared which would be soluble in ethyl alcohol and then by means of the constant E.M.E. existing between the value for alcohol and water the electrode potential of the element arrived at. With this idea in mind the autnor prepared some anhydrous chromic chloride. Metallic chromium was placed in a pyrex tube about three feet long and by passing dry chlorine over the red hot metal for some time a product was obtained. The chlorine was geherated by drop- ping concentrated hydrochloric acid upon crystals of potassium per- manganate. The gas was washed by passing through two bottles' of water and then a third bottle of sulfuric acid which served to remove the water. A U-tube containing calcium chloride was also placed in the chain for the same purpose. The metal glowed strong- ., :*>»-£--r-.-1 slc^-sj .. $A\iOsA \yj,xd^^ diiaifo Id &ed«iik«oi> . . .A ■' '" xi^r jv^X&d h»t^s ■ff{m c-1 -TjJtiJ? XiG^ 'hM «wr©xi€ JlV- ^ /- ; * '^■■’ * ■ . - V' ' ,^' c - J .:i*i©4? ^'ifv^''.'T’i t ^'Ss m qjL 9 siX : ^os^-io^.-.ed-- m- / . ,- . ^ i.- . .'■7''' , ' SM\-b}- s- : ) a^^no£i:ri/ig‘B^ V«^vX^ Xdlow 'Ip/o -lo^ -xXo>€*r a.4i r >1 tk. ai M Ik O.'t ', l?4‘‘ ’ ' j . - ’■■ > ' 4, • '* ' ■ ^ ■■' ^' viXi^l :itdi;j©*:^i O.- n c KiU &r .o <2 :£riim: .jft -. : , ^ at ■ . ■ ■ '>nw ' Yt0jft^i‘?,A fc»wM< irsf/1# OJ i^IluLUi a ax ds^oft eii^'J.I < . “.. ^ . . •■■•■. . '“W . V ■ Uw*. ■■■ •:•<# \ . t' ^ . ,-:,y , ^ ^-t! - - >T-*^ ' ^ .^V:...i;, •; a % ■' 4C-tov Qci jd^m ^0x4^ y*tQ -hi AJVJ,'! edJ, x4 J^-x6doc>t4^' 1x4^^ frfi 1 r- iii’4-i . . . ... i* '' i *!c . o/w X©ric^X}< idt us- - '**, V •' ' ^”a- . ■'-.^ ^ .;,/ •- ^ ^ ■ x.f>' V ._....- • - — - ■ - ■ -' - bi'JiSi ul 6i 0f » - , v^. . _ . ^ •• .V- dimndx>, 4i^ ixx4m ... _. . t vlfocf* ?9*X*^q -a ci L53^ltt%£m ms im^dr^'lXXAi Jod i>Oi 4.’ .-A'. . . Vi» Tl ^^v£a«w eui«, &fc^ a^fj -a“> ' Qf t6*rjs.e Mcut .4>X*s*A^iiXa t©%«i^4c-d - ‘ '■' ' -T- ■ "■ ’ Yijp : 3 ■0B,:^'’ BJiT/ -m^X*.MiuV\a^Xt>X-BCi ^^dsfX--V X b: ;^.rlJ-.v,_©vv'aeg> -’W'U-vi ‘ 5wu^' *iot tsX L > llLt^ l». .-’^ a .. ' ^ ^ ■-' * -- .- -'■ ^ ■— 1^ . ■ . ..:v y..^ - yfe ■. -yS ■*5t4nl^^_/ taS :' 6\v3v\f\9too^ 9*oo7vtost\3 ,9s>iniri'vt8lQb mj . »t ’^^'iivKdyiA^e' •J* •’ . f 1 *^ 1 *“^ • 4 ., •; I s’ ’^■'•‘V * •' %1 I ■-# 'f -i:. ^ * fr’ r * : ^ itc% ' ,-•'■> _ K'.'^'- 1 ' iVao-’Vl ••. J .' f ,, 2^,i0-\;l4?v >0‘ .— ^ ♦ — V.i ^ ,y‘~ A v*^ \r *4 >^/- ■- . /v '• ^ 'i-i " f,' '‘*‘‘ ■ ■' v^' ’;• A 41 w , . - its S,£, > * - ■ A V. (15) ly after the reaction had begun showing that it was endothermic. After cooling, the contents of the tube were removed and found to consist of a mixture of products. A fine apple blossom colored powder that had sublimed away from the rest of the mass and a large bulk of purple crystals containing some of the metal intermixed with them, were obtained. From discriptions found in the literature it was decided that both the crystalline mass and the fine powder were chromic chloride. It was found that the chromic chloride was insoluble in alcohox and hence this line of endeavor reached an end. A more soluble salt was sought after. There appeared to be no chromic salt that was easily prepared with the means at hand suitable for the purpose. In the literature a method for preparing chromous chloride from the chromic salt is discribed. The purple crystals discribed above were placed in a pyrex tube and it was hoped that by passing hydrogen over them in a heated condition they would be reduced to the easily soluble chromous chloride. The hydrogen was obtained from a cylinder of electrolyt- ic hydrogen. Even strongly heating the chromic chloride with-tne gas did not give a quantity of the chromous salt worth separating. There was some to be sure, but it was intermingled so thoroughly with the dark mass of residue that it was impossible to obtain even a sample of the salt without hoping to be able to work with it. A repetition of the operation using a fused quartz tube in order that higher temperatures might be reached, yielded the same kin d of results. A chromium electrode was prepared by electrolyzing a solution of chromic chloride with a current density of about four amperes I ' *' i’’* ” ^ ^ - » ' ' * ''S fl - ' . Crfcrr* «ftW xl ^Dsrfj 3Xii¥r^f(« lu/^ttcf j£fe!f i:ojwoi^0*s ft"\^U* .'-. >1 ^'f'tcXoo fcocoold dXqqxi A“ .«jro;;£»o'"iq lo eti^JXik 4^ to i'i'xfti-MJo o^* -ft ftcfl 9cif to M hen 9dj aon^xwst boaildire ^ .'■ . '''MJ 'V »■ / boxxcn:©J4i Xx4*^-5l let /j^q 9 f^ti^tASaoo .ihRith^o olqntni to jITi/cT ] ' ' ‘ T '■ " '■• I p^ijjpn^cii 9a^. ill bm/q^ «xioi>?qlh.oeije> , ,ij9ai&:f46 m-imrs^M -■^ ■ . V '■;■ '. ■ ' Z ' ''V ' 9i^vLt\i, btcft t . .Dfi^ jfta T^T>a9b£<4^"‘iO illlix Ssz.iiv S-toO'T'f^ Of? “Ocli Ci T Z ^ rx-J 'J *r-i ,^.y«Oq'T4/q Rii^ T^t ^'.CtHsi^tiV t^tl>4i (tJIi^ X' ft evijj >ofj jbXfc 00 ba£5^r^Xir;0;nx fus^ ii 4<^kiJ9, .i’ ■ ■- ■ . .' . .f*., • ■ ■-’ ■ ' / is • •” ../• i!y /' ^ ^JVw Ai:^-7tf4 0,;f eur* Jl ' V*.: . .^1 !Jd Xw r. %£}#.' o,- ifrirfjs (Kf oi s^^jerf ^Ti/oniiw j-X«« bify'^tofC^'Xqcaii: c * . ■ • ■ ;f fcf ■-' . b- cijt «mc0 >- ■ , ’ ’ . r, ?'••'.■ fc. '-r' '■'■ ■' ■ . . ./ 1 ••;■ - ' . a’ ■>'■ . ■ ■ U •‘>♦'^1 '*'' • ' •’''' . " ■ a'j* ^'* -t :.’ ^^pfrl.ti/Xoo 45 &AXsxi<9‘t•^'P»X© ■’•%. 3q‘;er:r; ' *' •* ■ '. . , 'r‘ . - , . . ,?Z *■■ ■ ; • “^3 '.By !" "" ’"■^ ' -V hit. • vjtrn f .r * - gay^^i rsr . ' iy ■ .;. V'» ^■ » per square centimeter !16) The chromium was plated upon a piece of platinum foil but was not very adherent. That is, due to some defect in the current density or the temperature the deposit was crystalline instead of the smooth coating that it had been hoped would be obtained. This defect, it is thought, could have been cor- rected had there been any real need for the metal. Since a suit- able electrolyte in which to make the determination had not been found the metal could not have been used as an electrode even, ir it had have been obtained in the form of an even smooth coating. r*‘ .> ^ .'••■f '- "•■L- " '1 ■to 9oei(f A riQ« ,*■'- -' • ‘ 'Vts •»•' ^ iM ixsqoxl rtuflicf tiMd Si 4kd4 :^iiiihozs*liiOQfrA eiU \c batfii a I oaiii5^e^p 2^1 ■• ■ ^ ■'■• ■ “* •'* 4 -icio,>- . evfi^f bluoo ^^d'saod^" o ju:? , JE^iiWW 6tx'or‘ **ix"o ii ooiiti^ *rp^ Moix £ba^ ’^oa V jotf fectt GOl^jjaljrio^efc nx \ nj - '-^.r a ‘ J, ® **'’' li: ,f;srp &f>cr*j^oc lo^ «a ♦« tx/^ Soci Xig5:W f \aa ;d.a;ra»s C 4 »e (u. to n^^ii'i- »tt/ ai i»riB^T* 0 f^ 46 »tf 'Sv:»il,-^ ■ v» .M r > 1 * 1 -,. “I ^ ? w’ ‘ 'v*J X_i'M .A '* f» I ■y,’^ ■■ L^ ^ > , V S' " • , . ' ■» - J/Al ' » . . H -|. - n f >- ,K' ')■-'• jf'». .»■•’■ - ’a\- . ■•. t ’ '\ ^ , HP ■'-!' V-a ^ r*V « , *>■< ‘^'V- . j- , .. -t. ;,' ’-t ■'■ .' ■■■f'te:^''.'^. >;i W. '■.T^ ^ . ■ tj i J i Ji; •** wsa-^JT ^BS— P.illpg ■ n i fl i ’) l'« 't ij! ilma ' *■'» - As" '‘-iw ■ .' ■ '^»'l i , '• " ■■ >. *• • \i tjl ;-. .'■;// r: , ^ 'v- V' X- >Vi ^'- ■ ■' - ^' J 4 » ( 17 ) A SUMMARY OF THE EXPERIMENTAL RESULTS OBTAINED. Finely divided zinc was prepared by tne electrolytic deposition or the metal upon a platinum wire from a solution of the chloride. Using the chain Zn/ZnClg/AgCl/Ag results were obtained which did not seem to warrant the use of the experiment as a class exper- iment . It was found that the method of Roderburg wherein tne difference of E.P. between absolute alcohol and water is made use of, was not applicable in the case of chromic chloride since it is not soluble in alcohol. An attempt to make anhydrous chromous chloride was a failure. .. t ( V : <• 1 .' ■ Tc ’■■ ■ ■ ^ f, . ■ V- Mr;^ . r ‘ ■ s, ■ £HT ?o Yawarog A' ;;' 3 V ■ - ^ . ViA ', - '-"J 5 ’ ‘ . - .,- „ , '' ‘ ,xj^i7i«oq9fi oi «*-a M/T^aX* 3 :B< 5 pc 9 lo a«i/ i/ie^t-i^ 0 *?' a»df‘^^oiS''fy'iXtfc • j L>t;£tiru<^^ii3 axij zX&i'fAtu 53i/tjr*iai>og coit-,©i» Jiaiifx Aisw ^ iA"VC.i ^ 7cn isir^,^o s^u^hBUi si WiA- iJOfi IcrfSali fc 7 «XcstfjJ , .'j jj 'i >, sld't^Ioe ;»on «i ^ri^ eopis si^iiolifo &i^jxo-5fa[D lo- asaa .. • - “«® "i ^■‘■' •'■■ w afj^aXjio aac4iiv*54iT» tw^T V •;, • ' 4 'S I ^^-+. -■ ■ '■ ■ c--:. -‘^.fer ■ ■• ' 7 . ’ V ■ . ' ' 7 ^' 4..*< t : iV^ ■- rt, 7 : ' ;-‘s ^ ^ 7 } 'SS ' * .■ .m.^M ' .. 7 «vP£U -i H <* , <*C^ ^ ' /- :.% , . ■ - ■, ' r' ='’■'* '-^“s '■’''' . £:-\ J- "' ? SL^- ( 18 ) BIBLIOGRAPHY I G.Horsch, Journal Am.Chem. 3ociety-41 ,178^ (Nov. 1919 ) 8 Kalilenburg, Trans .Am, Elect .Cliem.Soc .^,277 (1919 ) 3 .-jjoyes « Keyes. J.A.C.S. Vol .55 ,340 . 4 Pyys .Review. 6, 2rl-2tt2 (1915) D A.Pisher . ,Z.Anorg .Cliem.35 ,1 y0-8q& . 5 W.B. Marquis., J.A.C.S. 42, 1569. (1920) 7 Hittorf ,Zeit .Phys .Chem.^, 729-749 . (1893 ) o Hittorf, « « t» 30,481-507.(18^90 9 Zeit .Anorg .Chem . 8l ,17Q-80tj . 10 Covjper (3c Coles. Chem.Hews .ol,16, (19QQ ) II G.Horsch, J.A.C.S. 41,lvoV .(1919) IS A. Fisher, Z .Anorg .Chem.35,lY0-S08 . ... ( 19 ) ACKNOWLEDGMENT Tlie author wishes to take this opportunity to express his appreciation of the many helpful suggestions and criticisms received from Dr. Gerhard Dietrichson under whose direction this work w^s carried out.