Piperidiiie I S. electrode


INTRODUCTION

The osmotic theorbof the \.ciltaic cell lins led to iiiiiiieroii.cnrefiil iiieasureiiieiits c)f the dift'ereiices oi electrical 1)otenti:ii tli:it esist bet\\-eeii iiietalh ant1 tlie aqiieoiis .soliitioi~s of their s i t.s iii \vhicli the!, are iiiii~ier,setl. The iiieasiireiiieiit of singlt. poteiitiali ' ' becaiiie pwsilile 11-lieii 11: iiieaiis of the so-calleti (lroppiiig electrode oiie diffei-eiict. of potential bet\veeii a metal aiid the .solution in coiltact \vitli it liatl l~ecoiiie e~tablished. I n tlir iioriiial caloiiic.1 elec.trotie, .-LIercnry I iiierciiroiis chloride i 11 i i ( m i i a 1 soliitioii of potwsiiiiii cliloritlc, --the difference of poteii-tin1 hetweeii tlie iiietal id tlie soliitioii litis been fciiiiid to lit. 
(].<j6 volt,' tlie iiiiiius sigii iiidicating tliat tlie metal is positi\.e to \va r d t 11 e so 1 11 ti o 11. 1 I a 11 ! . 11 i e a s ii r eii i e 11 t s 11 a \-e 1 )e e ii iii u 1-1 e ..igaiiist this 1101-iiinl electrode, t i h i i i x it as a half cell miti dedilctiiig. its \ -d u e frniii t1.e total E. 31. F. of the coiiihiiiatic.)ii ineasiired. 

I L I

:;oliitioii of potassiuiii chloritlt~ iiisteacl of a noriiial mliitioii i,s ~ziiiplo!,etl has a iiioi-e coiistmt p t e i i t i a l aiid iii\-estigntors :II-C Icoiisquentlj. hegiiiniiig to use the it I O electrode i i i place of tilt. 
.~loriiinl electrode. few difference..; of potential 1ittn.eeil i1ieiaI.s 
;inti . d t s in the molten ,state have receiitlj. been ilieasuretl 1 )y t~ ;ordon. 4 The coiitact pottiitin1 hetlveen metal.: a n d non-aclt1e-Accorcliiig 1. 0 Kicliartls' tlie half cell iii n.liich a 011s soltitioiis of their salts has received almost no attention, probabl!. because of the widespread erroiieoiis idea that 11011aqiieoiis solntions of salts are geiierallj. such poor conductors of electricitjas to excliide tlie possiliility of the tneasiireiiieiit of the electromotive forces in qnestion. 
In I 894 H. C. Jones1 rneasiired tlie contact potential hetn-eeii silver aiid sil\-er nitrate solutions ; in the prepamtion of the latter water, et1iJ-l alcohol, inethj.1 alcohol arid acetoiie lvere iised as solvents. The coi~iliinatioiis iiieasured were made iip as follons : 
-4gl -l g S Oin water, -l g X O , in alcohol l.ig, iiietliyl alcohol aiid acetoiie being nsed in tiirii iiisteatl of alcoliol. T h e solutions used a1n.aJ.s coiitaiiiecl the saiiie aiiioniit of salt per liter. T h e electrode in the 11011-aqiieotis solutioii was in each case fonnd to be the positive pole of tlie cliaiii. T h e liigliest E. 11. E-' . ineasured \vas 0.1Sz yolt. iu tlie case n h e r e acetoiic was used as sol!-ent ; when iiiethyl and ethg-1 alcoliol \\-ere iisecl, the highest \ d u e s found were 0.1 2 3 volt aiicl 0.130 1-olt respectivel!.. 
Son, since these tioii-aqiieoiis solutions of sillw-nitrate do not condnct electricitj. a? well as aqueous solutioiis. the former contain fen-er ioiis according to the tlieorg, of electroljtic dissociation. If with Seriist it be assiiiiied that the metal lias aii electrol!.tic solution tension and tliat the difference of potential lietween the i1iet:tl and the solution is deteriiiiiied lij, the iiiagiiittide of the solntioii tensioii atid that of osniotic pressiire of the silver ions, i i i the soliition, then (if for a moment the assiiinptioii lie iiiacle tliat tlie solution teiision does not varj. when the solvent is cliaiiged) the sili.er in tlie 11011aqueous solution ought to he the iieg-ati\.e pole of the a1ioi.e coiiibiiiatioii. Since esperiiiieiit slion-s that tlie opposite is the case, Joiies concludes that the solution teiisioii of silver is differelit iii acetoiie and alcoholic soltitioiis froiii \\-hat it is iii aqueous solutioiis ; in other words, the soiution teiisioii of sil\.er is not a coiistant for all solvents of its salts, titit \.aries with the nature of the sol\-eiit iii which the silver salts ai-e dissolved. He states that the same nil1 pi-~bably be foiiiicl to lie true for other metals also. where the alcoholic soliitioiis touch the aqueous solutions atid also n-liere the t\vo alcaholic solutions coiiie iiito contact with each other. H e found esperiiiientally that xvliile silver in silver iiitrate solution in ethJ.1 alcohol is iiiore positii-e toward tlie aqueous solu tioii tliaii i.i sil\-et-iii sil\-er iiitrate soliitioii in iiietli?.l alcoliol, sill-er iii tlie latter solution is positi\-e to\vard silver i n the ethyl alcohol soliitioii, -to lie siire by less than 0.01 l-olt. Accorrliiig to Joiies this n-onld indicate that a difference of poteutial exists bet\veeii the alcoholic solutions a t their poiiits of contact. niit el-eii if the sill-er in the eth!-l alcohol had beeii positi\.r toward that iii tlie iiieth\.l alcoh(j1, tliis \vonld not 1ia1-e iiiatle it less pi-obable that an E. 11. F. exists at tlie junction of tlie t\vcJ solutioiis. I t is \vel1 kiio\vii that the point of coiitact of two electrolJ-tes j s in g-enei-al tlici seat of m i E. 11. F., n.liicli, hon-e\-er. 
011 the ~vliolc is not great, niiiouiitiiig to only a few 1iuiiclretlth.i of a I-olt at iiiost as a r1L.e. T h e iiieasttreiiieiits of J o i i e too n-ould indicate that the E. 11. E'. at the contact of two soliitioiis is slight. 
The ohject of tlie present iiivestigatioii is to tleteriiiiiie tlie d iff e reiices o f elect i-i cnl 1x1 t eii t i a 1 t 1 1 ;it e s i s t bet \v e e i i 111 e tal s a ii ci lxrioiis iioii-~iciueous so:utioiis of tlieir salts. TYliile the iiirii t i object a t present is to acciiiiiiilate facts, the resiilts ol)taiiied \vi11 a150 be vie\ved iii the light of the osinotic theor!. of tlie galixiiic cell ;is de\-eloped 11y Seriist aiid Ostn.alc1 as far as t-xistiiig (lata esseiitial for tliis piirpose \vi11 pei-iiiit. I n a pi-e\.ioiih rirticle' tlie electrical coiitluctil-ity ~) f a iiuiiiber of 11011-aqiieoiis wliitioiis \\.as prewite(1. Tliese contliicti\.itJ. iiieasiireiiieiits lin\.e since 1)ern coiitiiiuetl li!. 11r. -4. 1 ' . Liiicolii, n-liosc results :ire re:id!-for-1)111?licatioii and \vi11 appear sliortl!. in tlie pages of tliis journal. Tlie iireseiit article coiitaiii.< tlie rebiilts of oiiti of : L series of iiivestig-atioiis of iioii-aqiieoiis electrolytic solution,< tlint is in proaress i i i tliis laliorntor!-. 
Method of Experimentation and Materials Employed. -I lit-electroiiioti\.c forces \\-ere iiieasiiretl ti!. ~i i t a i i s of tiir coiiilmisatioii iiietliocl c,f 1'og:rffeiitlori. using a Lippiii:iiiii's electroiiieter as : i zero iiistruiiieiit.' 'rlic Iritter ~v n ; aiiffiiciriitl!. 5itiT-e t o perinit iiiensiirt'iiieiits to lie made to oiie iiiillii.olt. In a few cases, liowe\-er, ivhere tlie soliitioiis u w e ver)-poor coildnctors of electricit!. this clcgree of accurac!was not quite at taiiie(1, Leclanclie cell \vas used as tlie '' working eleiiieiit '' iii the coiiipeiisatioii process. T h e E. 11. F. of tliii; 1,eclanclib cell n-as determined hefore anti after each iiiemireiiieiit 11). iiieaiis of a Helmholtz one \.olt eleiiient : the latter was iii tiirii coiiipai-ed at times \\-it11 a Clai-l; eleiiient and al,s;O with a IT-estoii eleiiient. 
The three staiidard eleiiieiits slicnved escellent agreeiiieiit tlirotigliout the iii\.estiptioii, niid the E:. 11. F. of the 1,eclanche cell also lmxnie reiiiarlial)l>. constant after a tiiiie. 
111 n iiuiiiher of cases iiieasiireiiieiits ivere iiiade directlj. 
against a iioriiial calomel electrode, t h e E. 11. F. of which \vas I n fact all the $'.siiig-le poteiitials " gi::i\.eii l)elo\r are calciilatecl 011 this ~-n l i i e of tlie iioriiial electrode a.5 a bask. 
It \vas connected n i t l i the iioi-iiial electrode and the I:. 11. F. of the coiiiliinatioii \vas foiiiiil to lie 0.053 1-olt. .lltlioug!i the measurement i m c ; repeated a t \m-ioiis times tlie saiiie resiilt \vas aln-a!-s olitaiiied. A\ student in this lalmratoi-?., who liad iiidepeiideiitl!. 
prepared two of thew electrodes;, :ilscu ohtaiiied 0.0 53 \-olt on 
iiieasuriiq the E. 11. P. of the electrodes \\.lien coiiihiiied. T h i s 
iiiakes the value of tlie ir I O electrode ~ ~ 0.613 \.olt, the E. 11. E'. 
at the cotitact of the 7l I anti I I IO soliitioiis lxiiig disregarclerl in iiiakiiix tlie calciilatioii. The general nrraiigenieiit of the xmltaic coiiiliiiintioiis iiieasuretl \vas as follon-s : The metals clipped into solutions contained in test-tiihes or sinal1 I)eakers placed 011 3 le\-el aiid filled to the s n i i i ~ height. The connection hetiveeii t h e tn-o 1,essels \vas made 1 1 )iiieaiis of a strip of :,.id filter-paper folded to sei.eral thicktiessei; ; thus t h e solutions ,soaked into tlie filter-paper from each end, and wlieii the liqiiids met i n the pores of the paper near the iiiiddle of tlie strip the clectricnl coiiiiectioii \vas establislietl aiid tlie iiieasureiiieiit could be made u-ithoiit iiiuch daiiger of either of the ,solutioiis passiiix ol-er iiito tlie other dish. 
with hut unietl to he -0.56 iwlt. 
..I 12 IO caloriiel electrode \vas also prepared. 
the other metal is brought iiito contact with the solution, but tlie last traces of silver require coiisideralile tiiiie for their removal. I t snggested itself tliat tlie process coiild lie Iiui-riecl electro-l>-ziiig the silver nitrate solution, iisiiig the metal n-hose nitrate is desired as anode. In the case of tlie pyridine solution. tlie liqiiid turned dark e\-eii wheii a weak current \\-as e i i i p l o ) d , aiid so it was decided not to iise this iiietliotl, for it \\-as e\-itletit that sonit' secondary change was taking place. The follo\ving iiietals coiiipletely replace silver in a silr-er nitrate solution in pj-ridiiie : iiiagiiesiutii, zinc, cadiiiiiiiii, thallinin, lead, copper. Mercury seems to replace s i l r w oiilj. partiall?., ivliiie iron, nickel, cobalt, aliuiiiniiiii, gold and piatiiiuiii ilia>-reiiiaiii a loiig time iii tlie silver nitrate solution without any 1.isilile cliange, their surfaces remaining Iierfectl?. bright. T h e solution of silver iiitrate in aiiiliiie heliar-es in an aiialogoiis iiiaiiiier toward the iiietals iiieiitioned. In tlie case of this solution it \vas also ascertaiiied that tin, antimony aiid bisniutli do not precipitate the sil\.er. IYliether the fact that the iiietals aliow iiaiiied do not replace silver in these solutions is to lie explained IIJ. the sparing solubility of their iiitrates-ivliicli \voiiltl lia1.e to formlias iiot beeii cleteriiiiiietl. I t is easy to see rvliy gold and p1:ttinuiii should not replace silver\ hiit tlie 1ieliai.ior of the other iiietals is not so readil!-esplaiiietl. This matter will lie taken u p again in connection with another iiir-estigation. 
T h e electrodes iisetl rvere in tlie fonn of sticks or foil. The). were of the purest iiictals olitaiiialile in the niarket. Tile electrodes \\-ere carefull!-cleaned n-it11 emery cloth until theiisnrfaces were briglit. Tliej-\!-ere tlieii \\-aslieti rvitli \vater and dried rvitli cleaii filter-paper. The electrodes \\-ere tliiis cleaiisetl before each deteriiiinatioii ; :uid iieitlier the emery cloth nor the filter-paper \vas iisetl more tliaii once, iien-pieces beiiig eiiiplo\-ecl each tiiiie so as to giiartl against coiitaiiiination of tlie surface5 of the metal-;. In t l i o x \.oltaic chains i i i \\-liicli 110th electrodes were of the saiiie metal, special care \\-as takeii to test the elcctrodes in oiic ant1 tlie same wlutioii to see r\-lietliei-tile!, ivere alike ; and, as a rule, tlie electrodes iised in tlie cliaiii \\-ere e s -cliatiged after being i t asheti aitd wiped nit11 cleaii new filterpaper -:iiid tile E: . 11. F. of the cc)tnhination n-as then iiieasnred again. T h e resnlts so ohtaiiied a l i v n ~-s :ig-reed to a iiiilli\mlt. T h e iiieasiireiiieiits \yere i i i all cases tiiatle a t i-ootii tetiiperatiire, alioiit 
2 0 C c. Presentation of 'Results. -Sill-er nitrate dissolves in : L i-elati~.el!-large nuiiilic-r of sol\.eiits !,iclditig-solutions that coil- clitct. electricit!.. Tive11t!.
-h1r i / IO soliitions were Iirepared, n tiiffcrent .sol~~etit Iieitix-used i i i ericli caw, : ~n d tlie differences ~f po t eii t i a 1 lie t ivee t i th esc sol 11 t itiiis at it1 I ii et all i c si 1 1' cr clippi t tg into tlieiii n-ere d~terii~iiie(l. T h e iiiiiiil)cr of diffet-etit solvents used i i i p ~' e p r i i i g -tlie .soliiti:itis ( ~f salts o f otlicr iiietals is Ilot ;is great. 111 tlie calcii1:itio:i of so-c:rilletl .siiiKle or alixilute potenti:ils, tlie 1'. 11. F. at tlie cotitact ( ~f ' tlie liqiiicls Itas t l i r o i i ~i i o i ~t l ~e t i ilisiqarclec!. Tliese electrc~iiioti\-c forces are a,\ : I rule iiiinll, 1)iit in soiiie cases the!. aiiicniiit to sei-era1 li~itidi-edtlis o f :I [wit. .Ail esaniiiintioii of tlie resLi1ts g-iiwi lxlo\v \vi11 slioiv this so tliat :iicntal cleteriiiiiiatioii o f these electroilloti r c e s lins tliiii far atid liecnitse. i t i iiiati!. cases at 1 t ~ t 11 e 1 2 t 11 e I' co 111 111 i ca t et1 r!. i i i 11ir1kiiig .\iicli tlctel-iiiitiatic)iis \\-oultl iiiake it o olitniti siifficieiitI>. accurate results liecause of tile liigli resistance of tlie w:iitioiis. 
.Is statetl aliol-e. d l tlie alisoliite poteiitinls xiveii nix: 1-eferr-ed to tlint of the tlorli~al (?nl(JlllCA1 elecLro(le as ljeiiig ~~ 0.,6 volt, 1111 t iiie-i.s~ii-etiietits iverc: tiot a l i ~x ! . ~ tti:itlc. tlirectl!axaiiist tliis electrode. . I I / I O soliitioti of sill-er iiitrnte in p!~icliiie l i e i i i ~ a gooti contluotoi-, tlie tli tiereiice of poteiitinl hetiveeii it niitl silver coiild littiie:isiired ncciirate!!.. It i\ fo11nd to 1)C ".j;.3 \Y)lt. 
\ I a t i > . of the cotiilinations. p:irticitl:irl~ tliose made [vith soliitions \vlic)se soli-ents do not t i i i s ivitli \rater or are hiit sliglitl!. soliil~le i n n-ater, iyere tiiensiired agaitiht sili.er dippiiigiii n i / I O .soliiticiti of h i l i w -nitrate i t i p!~iditie and tlic siii,yle potentials witglit \vere tlieti calci~lntetl. 111 a f m v cases iiiea>ureiiieiits ivci-e riiatle iibiiig silyei-it1 . formed vias tlieii iiieasiired aiid the qiiigle poteiitial sought calciilated in each case. This coiirsti vas talieii in order that the separate tleteriiiiiiatioiis iiiiglit act as a clieck the oiie upon the otlier. 
Tlie results of the iiieasureiiieiits arc given in tlie following talile. T h e coiiibiiiatioiis are nuinher-ed iii tlie first coliiiiiii in order to facilitate futiire reference to theiii. Tlie secoiid coliiiiiii gives in detail tlie 1-oltaic cliaiiis iiieasiii-etl, Tlie coiiiiiioii way of n-i-itiiig theiii has lieeii adopted s u that fiirther explanations \vi11 not be iiecessarj-. 
plus sign indicates tlie positive pole of the cliaiii, A11 solutions coiitaiii one-teiitli of a grain eqiiivaleiit of salt 1x1-liter niiless othenvise indicated. IT'liei-e iio iiieiitioii of tlie Fait coiitaiiied iii the sciliitioii is iiiacle, sil\-ei-nitrate \\'as used. Tlie solI.eiits are gii-en iii all ca5e.s;. T h e tliird col-11iiii1 coiitaiiis the E. 11. F. of tlie total coiiibiiiatioii, aiid tlie fourtli coliiiiiii coiitaiiis tlie alxoliite E. 11. E'. of the j-i-st htr/f' of tlie cliaiii, tlie calculatioii lieiiigiiiade as alread!. esplaiiied. 111 all cases the electroiiiotii-e forces are gi\.eii in 1-olts. I t appears fi-oiii the a h -e tahle that tlie single poteiitial of a metal ton.ard a solutioii \-aries soiiien-hat accordiiig as the iiii.asiireiiieiit i.; iiiade directl!. against the iioriiial electrode or a p i i i s t soiiie otlier half cell, ~\ h i c h has heeii tleteriiiiiied direct:\-1 ) ~iiieasurriiieiit against tlie iioriiial electrode. It will he noticed that these ~-ariatioiis affect the secoiitl tleciiiial place ; the!. are due to tlie E. 11. F. a t the juiiction of the solutions. \vliicli were iieglectetl in calciilatiiig the &ingle poteiitials as stated a11ove. 
Discussion of Results, -TYlieii tlie foregoing re.siilts are regxcled ivitlioiit reference to theor)-the follo\viiip facts become e1.i d e i i t . 
Silver is pohitive toward all thc solutioiis i n which it n-as tested 1 S o s . I to 45 j. It is inost positive toward the solution iii acetolie and least toivard that i n 11rop~~lainiiie. The coiitact-potentials of silver :itid the aqueous and :dcoholic solutionsincluding gl\.ceriiie aiid gl\-coli -\os. I to IS 1 are of tlie same general order, the differences being 0 1 1 1 ~~ a fen-Iiuiidreclt1i.s of a I-olt. 
Tyliile silver is iiiore positii-e ton-:\rcl the solution i i i acetone !So,<. 19 an.'. 201 tliaii ton-aid aci:ieoiis or alcoliolic soliitioiis, it is iiioi-e positive to\vai-tl the latter tlinii to\\-arcl the solutioii in acetonitrile j S o . 2 I ). Toxvartl tlie lmizoiiiti-ile solution (So.;. ' 3 xiid 2 4 ) and also ton-arc1 the sol,.ition iii etli!-l c!xiiacet:ite sily,.vr is alioiit 3.; po,siti\-e as to\\-ard the acliieotis and alcoliolic soliiticjn<. Ton.artl tlie so1:itioii in p!.ri:liiie i So.<. 26 aii.1 2 ; ) sil\.ei-i:; oiil!alioiit one-half as positive as ton-aid the alcoliolic soliitioii. TYliile tliis iiietal is slixlitl!. iiiore positi\.e to\\-ai-tl tlie io!utioii iii qiiiiioliiie i S o . 29) than ton-aid tlie ioliitioii iii pJ.i-idiiiey i t is lecs positive ton-.ii-cl tli-s31:itioii i!i pipxidin: ( So.,. 33 aiid 3 I j tliaii ton-aid the 1at;er. T h e coiit:~ct-p,)teiitinl 1)etn-eeii silI-ei-:ind the so1utio:i iii aiiiliiie I S o . 3 2 1 is tlie same :is tliat hetn-ccii this iiietal aiid the solntioiis in li/-xL-lidiiie ( S o . 36) and o-toliiidine (So. 3 5 1 ~ tlie 1-ariatioii in the caw of the latter 1)eiii:i. i n the t l i i i d clecinial p l a c ~. I t n-ill lw noted that tlie lxst tlirtc sol\-eiits iiieiitioiied are closel~. related iii that eacli coiitaiii.: a i i aiiiitl i groiip iii place of oiie of tlie h!~tllcg-eiis of the 1,eiizme 1-i iig. T o \\-ni-d t 11 e so 1 11 ti ( 1 I is i 11 iii c' t 11 !.l-: I ii tl tl i i i i et 1 I j.1 :iii i 1 i i i c I S o s . 33 ant1 34) sil\.eii.s alic.)iit as po.*iti\-e a tci\~arcl tlie so111tioiih i i i g-l~.col j So. 15 ) aii(-l gl>.cvi-ii:e j So. 18) I-e.~l:ecti\-el!., Tc i\vnrtl tlie w1utioii.s iii i1-l>iit!.19 is01 )!it!.l~ aiii!.l :ii:tl lleiiz!.l aiiiiiie j S o s . 3 ; to 45 ) sil\.er is IC.;.; 
itil-e tlinii tci\\.ai-d a:i!. of the (;tiler so1utioii.s e r c q i t possihl!. tli: I pipridiiie. TT7iile the E: . 11. F. 
:it tlie coiitact of s i l \ w and tlie .soliitioii.; in these ciiiiiiies is of tlie saiiie geiieral order, it s e e i i i ~ ii-oiii ;I coiii1xirisoii ut' S o i . 3;. jc, and 43 c)r S o s . 3 S , 40% 44 niitl 4~5, t1i:it tlie iiietal llecoiiies iiiorc positi\.c ton-ard tlie sol otioiih in tlie aiiiiiies tli:it are liiglieii i i tlie lioiiiologous sci-ies or are riclier i i i cai-lxiii coiiteiit. h1ion.s tliat sill-er is dightl!. iiim-c posi:i\.e toirarcl the solutioii i i i i,,olitit!.l aiiiiiie tliaii ton-arc1 that in /l..liiit!.l aiiiiiie. SilI-er i-winv\vliat iess positive ton-an1 a ,soltition of xilr.ei-c!miitle iii ll!.~-itliiir t l i m to\\-ai-tl oiie of .-il\.er iiitratc i i i tlie saiiie sol\.eiit ; I So. 46 sliows. From aii iiisiiectioii of S o s . I to .+s, i t :ippear that contact-poteiitials bet\\-eeii a iiietal aiitl soliitioiis iii \-ai-ioii,< solvents, each coiitainiiig tlie same quaiitit!. of a salt of the metal per liter, depend oii tlie chemical nature of the solvents ; in the case of solvents of a siiiiilar chemical nature these differences of potential are approximately tlie same, this approsiiiiatioii being the better the more closely tlie solvents are related to one an- other. 
llagiiesiuiii is much less iiegrrtive toward solutions of iiiagiie- Cadmiiun is soiiiewliat more iiegati\-e tonard a solution of cacliniuiii nitrate in pyridine than toward a solutioii of this salt in water ( S o s . 63 to 65 ). Seuiiiann' found the E. 11. F. at the contact of this metal aitd a normal ayiieoiis solution of its nitrate to be -0 . 1 2 2 volt. 
sium
T h e single case in which tlialliuiii was iised ( S o . 66) n-oiild indicate that this metal is negative toward a p!.ritliiie solution of its nitrate to a11 extent riot l-er!. digerelit froin n h n t its potential is toward an aqiieous solution. Seniiiniiii' found the E. 31. F. at the contact of thalliiim and a n o r n ~a l , aqueous solution of its nitrate to he ~~ 0. I 12 1-olt. 
Lead is iiiiicli iiiore positive ton-arc1 lead nitrate solutions in p!.ridine aiid aniline ( S o s . 6;. to 7 0 ) tliaii ton.ar(l the aqueou:, solution of this salt, Seuiiiann' having foundo. I I 5 1-olt to lit. 
the E. 11. F. at tlie contact of this metal and a iioriiial aqueonh solution of its nitrate. Lead then beliaI.es t o w m l the pyridiiie soliition of its nitrate in a iiiaiiiier opposite to that iii ivliicli silver acts ton-ard a solution of its nitrate in this sol\.eiit. 
Copper is probahl!. soinewliat less positive ton.src1 the solutioii of its nitrate in aniline ( S o . 7 2 ) than tonard the aqueous solution of this salt. Seuiiiann'sz \ d u e for the E. 31. F. a t tlie contact of copper and a noriiinl aqueoiis solution of its nitrate is ~~~~ 0.61 ,j 1-olt. Copper is certainl!. iiiucli more positi1.e ton-art1 the solution of its siilpliate in iiieth!.l alcohol ( S o . ;.3) tliaii toward the aqueous solution of this salt. Xeuiiiann2 foiiiid ~~~ 0.515 volt for tlie E. 31. F. at tlie coiitact of copper and a noriiial aciiieous solution of its sulpliate. Ton-art1 tlie p>.ridine solutioii of its nitrate ( S o . 7 I copper is proba111~-less p s i t i \ -e tliaii ton-arc1 the corresponding aqiieoii.5 soliitioii. T h e saturated solution of copper sulphate iii methyl alcohol coiicliicts i-er!. p o r l ~. . solution of antinion!-trichloride for tlie latter dissoll-es in \vater oiil?. in preseiice of an exceFs of acid. Ton-arc1 tlie soliitioii in nitrobenzene ( S o s . 7s and 79) aiitiiiioii!. is much more positive tliaii tonard the alcoholic solutioiis. T h e alcoholic solutions conduct better tliaii do those i n nitrobenzene.' 
Risiiiuth is pohitiJ-e toivard solutions of its trichloride in ethJ.1 niid iiieth!.l .~lcoliol ( S o s . SO mid S I to approxiiiiatel\-tlie same extent that aiitiiiioii!-is positii-e to\\-ard the solutions of its trichloricle i n these solI-eiits.' 
T o ward fer i-i c c 11 1 01-i (1 e sol 11 ti 01: s i 11 a1 c oh 01, ii it 1-0 he 11% eii e ant1 orthonitrotoluene iron is iiiiicli iiiore positil-e than to\\-arcl the rolution of this salt iii lvater (coiiipare Sos. 82, 81, S6 and I'latiiiuiii is 11101-e positi1.e to\\-nrd an aqueous t l m l ton-arc1 a11 alcoholic solution of ferric chloride ( S o s . 83 and 8, ; hut tonard solutions of this salt iii iiitrolieiizene and ortlioiiitrotoluene i Sos. 87 atid Sgi it is iniicli more positi\-e than ton.arc1 t h e nciiieoiis solution. T h e stud!. of the ro-called os!dation antl reduction chains in which solvents otlier than n-ater are used is evidentl!. full of iiiterest. I t will recei\-e more attention iii the future. T h e fen. iiieahiii-eiiieiits here given are of course entirely insufficient to make ail!. geiieral st, t emeiits. 
I desire lierc oiicc iiiore to call special attention to the fact that, while the E. 11. F. at the coiitact of a metal and a solution These results caiiiiot he coiiiparecl clirectl!. nitli ai1 acliieoiis 
. ~~ ~ - ' Compare Kalileiil)ei-~ m i l 1,incolii. 1. c.
Seuiiiaiiii I 1. c. I foiincl the E. 31. 1:. at t h e cunt,ict of m t i i n o n y antl antiiiioiiy trichloride iii \\atcr plus li!~tlrochloric acid to he 0.376 volt. antl a t t h e contact [If 1)iwiutli ant1 t h e aci(lifiet1 ac1ueo:is solutioii of its trichloride lie tletermined the E;. 31. F. to he ~~~ 0.31 j volt. 
of its salt 1-aries with the nature of the solvent, this yariation may differ, not only as to degree but also as to sense or direction, from the potential that the metal exhihits toward, for example, an aqueous solution of the salt. T h e results upon whicli this statement is based 1x11-e just been disciissecl in detail aiid hence it is nilnecessary to consider the111 again here. 

The results viewed in t h e light of t h e osmotic theory of

t h e cell. -1Ylien a metal dips into an aqueous solution of one of its salts the difference of potential between it aiid tlie solutioii may be calculated according to the formula : 
where T is the difference of potential in volt5, R the gas constant yo-called, T the absolute temperatnre, 12 the xdence of the nietal, e the constant of Farada>.'s Ian-. and P anti p the electrolytic solution teiisioii of the metal and the osniotic pressure of RT it\ ions in the solution respectivel!. 
-i t a gil en teiiiperatiire C is a constant ; at rooin teinperature ( 2 0 " C) tlie formula heconies T-=: ~~~ log --, when the cotiinion instead of tlie natural logarithiii is iised. For ;I given metal u, is also a constant, .and hence the value of ~i depeiids up011 the ratio of the soliitioii tension, 1') to the osmotic pressure of the metallic ions, p . 2,s 
.the constant of Faraday's law is inr-olved in this forinula, it is necessar!. before attempting to appl!. tlie same to non-aqiieoiis :jolutio11s to inquire wlietlier E:arada!-'s law holds for the latter. 
On this point I desire to s a ! . , that I 1iai.e electrolJxed a number (of the non-acjiieoiis solutions iiieiitioiiecl abo\-e, having a silr.er voltaiiieter in tlie same circuit. and the aniounts of tlie metals deposited iii the \-arious cnses tested slion-that Farada!.'s Ianholds for these solutions as for aqueous solutions. T h e resiilts of this special investigation will lie published in another article. 
Son-the electrolytic solntion tension, P, is a h~.potlietical 0 . 0 7 S I 

E'

12. 

P

' Compare for instance LeHlanc's Elektrocheniie, 121 quaiitit!-aiid caii oiil!. lie foiind bj-use of the ahox-e foriiinla ~vlieii 7i aiid p are kiionii. -1s 7i is readil>-measured, aiid as the 1.aliie.q of it are gii.en ahove for B iiuiiiher of conibinationsiii n-liicli 11011-aqiieoiis solutions are einplo>.ed -with a degree of appi-osiiiiatioii sufficient for iiioqt piirposes:. tlie osmotic pressure of the io1i.q of the metal or j o n l ~. needs to lie ascertaiiied in each case iii order that the soliitioii tension of the iiietal or I ' may he calculated. T o ascertain / it is necesiar?. to deterniine tlie degree of electrolJtic clissociatioii of the salt iii tlie soliitioii. I t n-otild be exceeding-ly interesting to calcnlate tlicse values of P of tlie iiietals ton-arc1 I-arioiis sol\.ents. and to see whether the iiietals 1iai.e the Iiighe.;t electrol>.tic soliitioii tension toward those soli-eiits iii \vliicli their salts coiidnct best, aiid whether these soliitioii teiisioiis iiicrease witli tlie dielectric coiistaiits of tlie solT-ents, etc. Iii tlie case of aqiiroiis solutions of electrolytes the degree of dissociation, n knowledge of wliicli is iiecessar?. iii order to ascertain j, iiia?. he deteriiiiiied froni the electrical conductivity accorcliiigto tlie \vel~-kiio\vn formula, a = ' I , wliere a is the decree of dissociation and pr. a i d p r are tlie molecular coiiductivities at the \-oliiiiie 1' and at iiifiiiite dilution respecti\-el>,. T h e degree of dissociation can geiierall!. also be fouiid l i ~. iiieaiis of tlie fi-eezing--point or boiling-poiiit iiietliotls. In the case of the iioiinqiieoiis solutions in question, lio\ve\.er, the degree of dissociation caiiiiot be calculated from the electrical coiicliictil-it!., because p T is not k i i o ~i i . ~ T h e iiiolecular conducti\-it?of 11011-aqiieoiis solutions as a rnle increases ~i t l i the cliliitioii hut not I.er>. rapidly3 oiil~. rarel!. do the Tallies fouiid clear1)teiid toward a i i i x s i i i i i i i i i . ( Coinpare for esaiiiple the work of Kahlenberg am1 Liiicolii (1. c. ) and tlie refereiices there g i v e n ) T o be siire there are also iiiaii>. aqueous solutioiis that conduct bnt feehljaiid >.et tlie 1-alue of p p for them has been foiuid bJ-calculation making iise of the fact disco\.ered 11~. Kohlrauscli that the coiiductii-it!. to one-fourtli that of tlie corresponding aqueous solutions. -1s the latter conduct well ( t h e dissociation in 12 I O solution of sill-er nitrate in water is ahout 80 percent) tlie dissociation of the silver nitrate in pyridine oiiglit certainly to be capable of ineasurement by iiieaiis of the boiling-point method ; the relatiyely high boiling-point constant (30.07) of pyridine too lends empliasis to the latter statement. l y e ha\-e in a solution of silver nitrate in pyridine a fairly good conductor of electricity with a rnolecular weight so nearly normal that tlie conductivity cannot be accounted for by iiieaiis of the dissociation hypothesis.' lTeriierz has also foillid the iiiolecular weight of silver nitrate i n hetizonitrile to be iioriiial. TThile according to determinations made by Nr. Liiicolii these solutions conduct only about one-fonrth as well as do tlie p!.ridiiie solutions, yet, coiisicleriiig the high boiling-point constant of beiizoiiitrile (36.5 jj, it n.ould seem that even here the boiling-point method ought to yield molecular weights that are less than normal. 
From tlie facts here presented it seems clear that solutions ma!-conduct electricity fairly well and yet the dissolved substance iiiaj-possess a iioriiial iiiolecular weight, i. e. it inaj-be undissociated. Rut this point oiice established, the question arises, cannot conduction then in all solutions be explained withont assunling electrolj-tic dissociation? T o be sure then the high osmotic pressure aiid the correspondinglj-low molecular weights foiiiid in so inany cases, in aqueous solutions of electrolytes for instance, nould have to he accounted for otherwise than hjthe dissociatioii hypothesis. I t is not 111~-purpose to enter upon this matter in this connection. What has been said is sufficient to indicate that the data necessary to calcnlate the degree of dissociatioii of the salts in the non-aqueons solutions used i n the above galvanic chains are not at hand, and that in cases I The high electrical conductivity of salts in liquid ammonia (Cady, Jour, P I i ~-s , Clieni. I , 7 1 2 I 1S9; I 1, atid the hoiling-points of such solutions I Frankliii and Kraus, Xixi. Cheni. Jour. 2 0 , 84s ( rSgSj, are of interest in this connection. 
where the electrical coiiductii.it!, or the iiiolecular weight or both are known it is still not possible to get at the extent of the dissociation. Indeed as lias 1)eeii stated, the belia\.ior of soiiie of the solutions is such that it seems clear that while the!-do conduct, yet the dissolI.ed salt is undissociated aiid hence it seems like liunting the will-o-the-wisp to seek to ascertain tlie degree of dissociation in such cases. I t appears then frcliii xvhat has been said that tlie p of the abo\-e foriiiula is not o1)tainahle and coiiseqiieiitl!. the soliltion tensions of the metals toward the. \ x i o i l s solvents cannot he calculated. There is appnrentl!. oiie exception to this which lias heeii alluded to in a foot-note above. Sil\.er nitrate \vheii di5solved in acetoiiitrile conducts well, i n fact better' than when dissol\.ed in water. Dritoit aiid Fridericliz place p, for si1T.u nitrate in acetoiiitrile eqiial to 160: thougli ~v l i ~. the). choose this figiire is not quite evident. since their results shon-that the conductivitj-increases regularly with the dilution, the last four deteriiiiiiatioiis indicating 110 teiideiic!. ton-arc1 a iiiaxiiiium. Rut if 160 be taken as the J-alue of p I , tlie degree of dissociation in nlience I' ~ 4.82 IO-' atmospheres. Tlius it appears tliat tlie solution teiisioii of sil\-er toxvartl acetonitrile is greater tliaii to-wart1 Ivater. This liariiionizes ivitli tlie fact tliat in dilute soliitioiis sill-er nitrate coiitliictr; better in acetonitrile tliaii in \r-ater, though this difference i i i a ~. ~ at least i n part, lie diie to the fact that water is iiiore x-iscous tliaii acetonitrile. The dielectric coiistaiit of acetonitrile has iiot been deteriniiietl. to IIIJ-kno\vledge, so that a coiiiparisoii of the soliitioii tensioiis toivard the two solvents Lvitli tlie dielectric coii.5taiits of tlie latter cannot lie iiiatle. 
If it lie assumed tliat sill-er nitrate iii p!-ridiiie is dissociated to oiie-foiirtli the extext that it is i i i \\-:iter ( a i l assuiiiptioii t1i:it is open to strong oli,jectioiis because in the foriiier sollitions its coiitliicti\-it!is aliout oiie-fourth tliat in tlie latter. we have tlie foll(iiviiig upoii snlistituting tlie pi-opcr \-allies in ilie foriiiula, This \voultl iiieaii that sil\-er has a Xrcater tentleiicy to pass into tlie ionic condition iii p!.ridiiie tliaii i n water, which nonld not he in liariiion>. nitli the fact that tlie p>.ridiiie solutioiis do iiot coiidnct as ne11 as the aqtieoiis solutions. Again, altliougli the dielectric constant of p>.i-idiiie has appareiitl!. not lieeii deteriiiiiietl, it \vill> ,jiiclgiTig from a~ialog!., T-ery likel!. lie foiiiitl to lie iiincli lon-er tliaii that of water. 
Fiirtlier atteiiipts to calculate soliitioii teiisioiis will not lie iiiade, seeing tliat the reqiiisite \ d u e s of / are iiot a\.ailal)le. I t may 1~ n-ell. lion-ever, to call attentioii to one or t\vo further cases in a general \\-a!.. T h e difference of potential 1ietTveenfor instance-zinc and a solution of zinc cliloride into n-liicli it dips vai-ies froin 0 . 5 2 2 \.olt. i\~lien the sol\.elit is water, to ~ 0.066 volt, ~vlieii tlie soli-eiit i h ciiiinoline. Froiii this it is evideiit that tlie solution teiisioii of tlie metal rnnst tliiiiinisli very ,greati!-in the case iiieiitioiied. Sil\.er liehaves i n the opposite na!. to\vard these solvents, its contact-potential toward the aque-I Taketi froiii Sv. 2 6 . 011s ,solution heiiig ~ r . o r S T-olt aiicl tonard tlie qiiiiioline soliitioii -~~ 0.61; \.olt. Thi.; ~vould .~eeiiiiiigl!~ indicate that the so 1 ii ti o 11 t eiisi on of si l\-er i 5 %-rent e r tow a I-d qii i I 101 i i i e t 11 ail t (I \v a rcl \v:1tes. 
Tlie stiipeiic1oii.q \-dues that arc fouiid for tlit. soliitioii teiisimis of the metals toward \vnter according to tlit. foriiiiila gi\.eii :Iiio\-e are n-ell k i i ~~\ ~i i . 
Tlie reinarks recentlj. IYater l. Ag the concentration of the .lg ions in tlie pyridine solution he calculated according to the formula on the assumption that the solution tension of silver is tlie satlie toward pyridine as toward water, tlie result is that there are practicglly no silver ions in the pyridine solution, and that consequently the sili.er must be present in form of a complex ion. 
T h e fact that when ferric chloride and sill-er nitrate are hrouglit together in pyridine solutions no precipitation results would seem to argue in favor of this view. Hnt since silver chloride dissolves in pyridine and conducts, it may also be argued that silver ions and chlorine ions can exist side hg. side in pyridine (in a solvent he it reniemhered, that veq-likely has 3 lower dielectric constant than water) and that for this reason no precipitation occiirs. I t will not he contended that because nqneoils solutions of ferric chloride and, for instance, copper nitrate do not give a precipitate of copper chloride no chlorine ions or copper ioiis are present and no copper chloride is formed. T h e explanation is simply that all the prodiicts formed are soluble. 
There is no reason to suppose that in a sil\-er nitrate solution in p\-ridine the silI-er is pre5ent in form of a conplex ion. T h e facts are, tlie molecular weight of the salt in pyridine is normal and the compounds that pyridine forms s-ith silver nitrate are ( CjHTS)2.-lgSOj and ( C,H;S)q.AlgSO,.z -3 T h e latter compounds ]nay be regarded as silI-er nitrate n i t l i two and three molecules of pyridine of crystallization just as truly as the compound Cu(K03),.3H,0 is regarded as copper nitrate with three molecules of water of crystallization. S o one maintains that when tlie latter conipoiiiid is dissolved in water, copper is present in form of comples ions and there is no more reason for assuming that silver is present i n forin of complex ions in a pyridine solution of silver nitrate. The inference tlieii is that tlie relati\-el!-higher E. 11. E*. of tlie cliaiii last mentioned is due imiiil!. to tlie Iiigh solution tension of the iiietal toivard p!.ridiiie. 
Hut if this \.ien-he taken then in cmiiectioii n-itli tlie results of tlie last table, tlie coiiclusioii follon-s that the solution tension of silver ton-arc1 Ivater iiicrense.\ as p.i-idine is added to the latter. If this in turii lie atliiiittetl then i t ma!. he risked --~v l i y caiiiiot the solutioii teiisioii ton-arc1 \ v a t u be chaiigecl by d!,ssol\-iiig in the latter an!' siihstaiice. iolirl. licliiid or gaseoiis. I t is to lie borne iii iiiiiid that t1iii.q far tlie electroljtic solution teiisioii of a metal has alna!-.: been coiisiclered constant i at a g i v m temperatiire) to\vai-tl aqiieoiis soiutioii.~. 
If the theor!. of tlie elcctrol!.tic soliitioii teiisioii lie lieltl :it all, there seems no escape froiii tlie conclusion that the solution teiisioii l-aries for differsilt solvents and inistiires of' soi\.ents ; :iiitl lieiice tlie dissolved sulxtaiices -otlier rhan tlie simple ioiis of tlie metal in question -iiiaj. exert ai1 iiifliience i i i detei-iiiiiiiiig tlie difference of potential betn-eeii the metal aiitl tlie solution. If tlie solution teiisioii cliaiiges not oiil!-with tlie sol\-ent liut also n-itli the dissolx.et1 sulistaiices present, it is qtiestioiial)le, to sajtl i e 1 t a s t . \VI 1 et 11 er t 11 e 11 y pi t 11 esi s of a ii e 1 ec t roi !. t i c so 1 ii ti 011 ten -,~ioii is lielpfiil a t all. Certainlj-\vlieii tlie concentratioii uf a certniii kind of ion in a solution coiitaiiiiiig otlier sulistaiices also is to be foiiiicl I ) ! . the iisiial iiietliocl of iiieasiii-eiiieiit oi E. 11. F. in the app1ic;itioii of which tlie electrolj-tic solutioii tension is assiiiiiecl to lie constant. tlie f'nct that the latter ai;s~iiiiptioii is a safe one to malie iiiiist lie provccl i n each caw : lioiv tliib can he done, is not easy to see. / , ! i / i o r i r / o i ; 1 ~ (!i. / Y / j ~. i i m / c%c.ii/i.i/i:l,. I 7iii:,t,i.iifi, o j li .i.i[.oi/ <ij/, . l / ( / ( f i.s<iic i f r , io, /,\'qy. 

Tones

  discusses the qaestion as to the E. 11. F. at the points ~ ~ -~~ Zeit. 1)1i~-s, Clirrri. 14, 346 ~ 1Sg4:. 


(

  I inol in ~I I : c c ) , 14 i i>ercclit ~o l u t i o i i ) I SbCl, iii Etli!-l alcohol 1 Sh o.Or<; t : I mol i l l b113 c c , Sb 1 SbC1, iri lIeth!.l alcohol j (13 j pel-cent solutioti) CuSO, i n 3Ieth!-l alcohol 1 Cu 0 . 2 I 3 0 . 1 8 1 ($aturated i o ~u t i o i ~) S1i j SbC1, iii Sitrohenzeiie 1 S. electrode Sb I SbC1, i n Sitrobenzelie I ( I ~n o l it] 1&2:,.j c c ) ( I mol i l l I C ? ~ i c c ! SbCl, in Ethj-1 alcohol I Sh 0. 2 , ; Hi 1 BiC1, iii lIethy1 alcohol 1 S . electrode 0.039 Bi 1 BiCl., in Nethyl alcohol 1 ( I mol iii ~I I : Fe j FeCI, in Tf-ater 1 S . electrode (I io 11101 p e r liter) 




  of S o s . 39 aiicl 40 Ivitli S 42 aiid 4 I i-espeztii~j!. 




  To arcls s ol 11 t io ii s of ai1 t iiii 011 ! . t r i c 11 1 ori d e i ii 111 et 11 J. 1 ai1 d etliJ-1 alcoliols;, aiitiiiioiiJ. is fairl!. stroiigl!-positi1.e j Sos. 74 and --, , ). 




  5ilver iiitrate i l l acetonitrile Dutciit aiicl Friclerich. U L I ~~. Soc. Chirn.Pari. 19, \ ; >; , iS9S I place PI. eq~ial to 160. This figure will he used helow. 


a'

  J I I O solution is about 36.7 percent. T h e p of the abo\.e foriiiiila then becomes 0.367 of the osmotic pressure of one graiiiion coiitaiiieti in ten liters. -I t 20' C the osmotic pressure of one grain-ion in ten liters is 2480.2 grams or 1.9513 atiiiosplieres per sq. ciii. Substituti:ig in the formula tlieii we hai-e, rl -0 . S 6 2 , ' ~ o.ogS1 log -__ -__ 1.9513 ' 0.36:'whence P = 1.04 '~ IO-'^ atiiiospheres. If a siinilar calculatioti is inade for the aqueous solutioi:, assiiiiiing the degree of dissociation in IZ 10 solution to be 8 2 . I percent, we ha\-eTaken from No. I . above. 


?

  Compare Calm-Buchka. Chetiiie des Pyridiiis, 59. 




  I / I O aqitec)iis roliitioii of sili.er tiitrate a.s rl Ellrtllel. Collllllcllt Oil t1ii.s poilit seeill.. 



; 1i:llle at-!-, A n esperi-1lOt 1)tell attelil]ltecl 1iecatise tl1ey of se cot 1 tl ai->. i 111 poi-t ri 11 ce ~ lialf cell -wliose E. 31. F. was ascertaiiietl to h e -1.018 i.oltsaiid tlie siiigle poteiitials were calculated froiii the resnlts olitaiiied. T o ascertaiii : i siiigle potential, i. e. the E. 11. F. of a half cell, the latter vias coiiiiectecl siiccessivelj. nit11 tn-o or inore half cells (if E. 31. F. of the coiiiliiiiatioii pre\.iouslj. ascertaiiiecl ; the total E. 11. I : 


  ZiiC1, in 


	To. 61 6 2	s o . ,76 37 -Ig 1 11. Propylaiiiiiie , TVater 1 -Ig Voltaic Chain E. 31. F. Voltaic Chain Zii 1 ZriC1-iii Eth!.l alcohol 1 S . electrode 0.910 Xg 1 111. Xylidine 1.3.4. I Pyridine 1 -Ig 211 1 ZnC1, in Ethyl alcohol 1 ZnC1. in .38 .Ig 1 11. Propylaniiiie 1 Pjridiiie , Ag Tl'ater I 211 0. 19<i	r:. 31. F. 0.169 0.622 0 . 2 1 2
		39 X g , 11. Butylamiiie 1 \Vater 1 A g	0.60j
		40	-Ig 1 11. Hut! lamiiie 1 Pyridine 1 X g	0 . 2 0 3
	--i 3		
				0 . 8 3 2
		,j2	Z n 1 ZiiCl,? iii \vater	ZiiCIL in Pyridiiie 1 Ziio. 274
	--/ I	, ; n -j4		1.079
			'i\-ater 1 211	0.026	0.496
	;S		Z n 1 Z I ~I S O , , J~ in Pyridine 1 ZiiC1,; in Pyri-
	79		dine ~ Zn	0.234
	So		
	81		

50 Z n 1 z1iC1,~ iii \rater ~ S. electrode I .os2 51 Zii 1 ZiiCl? iii Pyridine I S. electrode Zii ' Ziii S O , i ? in PJ-ridiiie 1 S . electrode Zii 1 Ziii S O , )2 in Pyridiiie 1 s2 Pi, 1 1% S O ? in PJ-ridiiie 1 Pj-ridiiie 1 .ig 0. I;O Pli 1 Pb! S O , i ? iii Xiiiliiie 1 Aliiiliiie 1 ;ig 0 . 3 2 ; Cu 1 Cur S O , I ? ill Pyridine 1 Pyridine 1 Ag 0.366 Cu 1 Cui S O , I ? in Aniliiie 1 AIiiiIine 1 &ig 0 , 2 1 0 CU ~ CuSO, iii llethyl alcohol S. electrode 0. I 50 Sh 1 ShC1, in lIeth!.l alcohol j S. electrode o.oSh Sli 1 SliC1, iii Eth>-l alcohol 1 S. electrode 0.041 Sb i SlC1, iii lIeth\-l alcohol 1 :Satiirated soliition) +-(Saturated >olutioii> ( I ? 5 percent soliltioii: 


  iiitrate iii pyridine and aniline ( S o ? . 47 to 49) than it is toward an aqueous solution of this salt. Seuiiiaiin' foniid tlie E. 11. F. at tlie contact of magiiesiuni and an aqueous, iioriiial solution of iiiagnesiuiii iiitrate to be ~ 1.060 volts. T h e electromotive force at the coiitact of iiiagnesiuiii and tlie aniline solution differs hut slightly froin that at the contact of this metal and the pJ.ridine solution. I t is interesting to note that while silver is less positi1-e tonard solntioiis in aniline and pyridine than toward tlie aqueous solution magnesium is more positive 


	( S o s . 59 aiid 60). T h i s is very unusual, and it is to ni!. knowl-
	edge tlie first case found n-here zinc is positir-e to\vard the solu-
	tion in which it is immersed. I t ma!-be \vel1 to state in this
	connection that, jndging from tlie Iiioveinents of the mercury of
	the electrometer the solution of zinc nitrate in p!.ricliiie coiidiicts
	well, the corresponding solution in aniline conducts poorl!.. T h e
	solutions of zinc chloride in pyridiiie, quinoline and aniline are
	poor conductors; the alcoholic solution conducts somewhat
	11 et t er.	
	but toward the solution of this salt in aniline the metal is far
	less IiegatiL-e than toward tlie aqueous solution' (So. 58). T h e
	contact-potential of zinc in zinc cliloride in quinoline is slight
	and is in tlie sense that tlie metal is positive toward the solution
	' Zeit. pliys. Cliem. 14, 229 I rSg4 I .
	'' T h e contact-potentials hetween zinc and aqueous solutioiis of its cliloricle
	atid nitrate are not very different.	Seumanti 1. c. i found them to be -~ 0. j03
	volt and	0.473 volt respectively for norinal solutions.

(or less negative) toward the former than toward tlie latter.In other words, this n-ould indicate that silver and magnesium lie closer together in the electroclieniical series when p!.ridine and aniline solutions are under coiisideratioii tliaii \vlien aqueous solutions are considered.Ziiic is less negative (or more positive) toward zinc chloride in p!.ridine ( S o .51 i, aiiiliiie ( S o .ji), quinoline (Sos.59 aiid 60),and alcohol ( S o s . 61 aiid 62) than toward the aqueous solution ( S o . 50). Its beha\-ior is then similar to that of iiiagiiesiiiiii arid hence opposite to that of silver. Toward the solution of zinc nitrate in pyridine ( S o s . 53 to 5 6 ) > zinc is approxiinatel! as iiegati~ye as toward tlie aqueous solution" ( S o . 5 j also j 3 aiid 50) ; 


  iiiadt: 1 ) ~. I<. .J. I,elifeldtl concerning tlie estra\.agantfigiirestletlucetlfro111iiieas~ireiiieiits of E. 11.F.:ippear to tlie author \.erJ-tiinel!. i 11 deed.111order to ascertain Iio\v tlie E. 11.F. of tlie cliiiii, -1gi /z 10 *\g-S07 in P!.ridiiie,II .[o.IgSO iii l\7ater 1 Aig \.ni-ies, \vlieii in tlie first soliitioii.\vater11111sp!. iciiiic.iii\xi-ioiis~)rop(n-tioii,s is 11 .\ed as sol \.e ii t i 1i.y tead of p lire p .r i (1 i iie ~ t 11 e f o 11 u n,i iig tl e t e ri 11 iiiatioiis \vert.made.Tlie chain \vas tlie saiiie as jiist g -i \ ~i i ,i)utli soliitioiis i-eiiiaiiiiiig I / 10 tliroug-liout.Tlie solvent in the firrt solution \vas cliaiigecl as iiidicated iii the first coliiiiiii o f tlie f ~~l l o \ viiig table, while tlie secoiid coliiiiin gi\-es tlie total E. 11.F.Tht..sil\.er in the aqiieous solution \vas tlie positil-e pole of the COIII-1)iiiatioiis tliroughoiit.T h e coiiceiitratioiis are gi\.eiii i i part> o f \vater 11).\-oliiiiie to o n e part of pJ.ritiine.From the table it appears that silx-er dippinginto a sil\.er iiiti-ate soliition in pj.ric-liiie gradiiall!lxcoiiies iiiore positi\-e to-1v:u-d the soliitioii as the p.ridiiie is replaced l l ~. nxter : hiit tlie potential changes less rapidly thaii proportional to the a ~l ~o ~i i i t 


	C O l l C .			
	of water substituted.	
	If in the chain Ag 1 I I 1 0 . l g S 0 ~ in P!-ritliiie	ro*-IgSO i l l
	~	~~~~~~	~~~	~~
	' Zeit. pli>-s. Clierii. 26, 94 i IS$ ;,

ater 
I. c.
Piperidiiie I S. electrode