( 431 ) 



Chemistry. — ''On lln- polcnlldl-di ll'dwiwr, irliK-li occurs al fhr 

 siirfdct'. of conhicl of hro (///f'cnii/ iion-miscililc IkjKkIs, ii) 

 ir/u'ch (I (/isso/red c/cc/ro/i/fc In is dish-ihiitcd ilsi'If.'" liv 1)|-. .1. .1. 

 VAN Laak. ((Vjiimuinifated \)\ Prof. II. W. Uakihis Roozkhoom.) 



(Gominmiicated iu llie inccliug of Deceinl)er 27, l'.)()2.) 



I. It has ali-cady l)eon (leinoiislrated l»y Nki.'Nst '; in I<S1)2. lliat 

 a |)()lo)i(ial-(li(rerciH'e iiiust oeciir al llio snrlaco of coiilaef of hvo 

 li(|iii(ls, wliicli lie lou'clliei' in layers, such as for iiislaiico walci-aiid 

 phenol, on aeeonnt of Ihe inie([nal dislrihulion of di(Mienlral niohM'nk's 

 and die Ions of a dissoh'ed eleeli'olyh'. ll is li-ne, dial his expression 

 foi' the electi'onioti\e Ibree rehites to die ease, dial one of die Iwo 

 phcases is a solhl solution, but it will he pereeived al onee, dial die 

 same fornuda also applies to our ease "). 



There is, howevei-, at present no pi'ospeel of olilaininu' direet 

 measiireiuenls of this polential-diiierenee '). Hut as Rikskxi-'ki,!) ') has 

 lately been experimenting on the subject, althonuii in anolhei- (hre<'- 

 lion, it may be as well to give the exact theory of tiie phenoinenoii, 

 which 1 worked out about a yeai- ago, when engaged in ^vl•ilillg a 

 l»ook on electro-chemisli-y, whicli will be published later. 



Suppose we have a solution of KCl in the solvejits A^ and A^. 



A, A., 



If now e([uilibrium has been established between {\\q nnn-dissoclidcd, 

 electrically neutral poi'tions of the dissolved KCI in the two phases, 

 there need not be ecpiilibrimn between the Ions in the Iw t» sol\enls. 

 Indeed, e({uating the Iherniodynainie potentials for ('(pn\al('iil ipiaiili- 

 ties of the non-dissoeiated jxn-lions in the Iwo phases [ciinilihcinni 

 of pcN'titlon), we get : 



f'AV/, = '"at/, 



Bill the two dissociation-enuilibria give: 



^v-r/, = f'A- 



^VrA-^'V. 



yv'7, ' A', ' ' (■|^ 



C'onseipiently il will siiftice if 



,-..+ ^7., 



(1) 



(2) 

 (3) 



1) Zeitschr. fur Fhysik. Chemie 9, 137 (1892). 

 =) Compare Rir.sExrKLn. Wiod. Ann. (i) 8, (d7 (l'.»ü2). 

 ■') Ibid., 1. <•,. 



') Nernst mid UiKsKM r.i.i>, I.e. |i. il(»n lioS; IliKsKNKicLu, GO*.)— G15: OK)— G24; 

 id. luaug. Di:>s., CöUiuëeu IWl ; ihnour, Wied. Ann. (4) 9, 243—245 (1902). 



