MI<;RATIO\ VELOCI. HE PROTEIX h 



ms in the origin of the electr. rmer ap 



as a polyvalent base or acid, the Lit: Xernst electrode, 



sending out metal ions. There is a remarkable agreement 

 between the chemical and th .emical conceptions of 



the mechanism. \Ye may assume, nevertheless, that the charge 

 of a colloidal metal particle may correspond to the distribution 

 on a charged conductor, whereas that on a protein molecule is 

 probably localised a: the discrete points where the acid or 

 valencies occur. 



It is well known that potential differences occur at the 

 boundary between two solutions of electrolytes when they con- 

 tain ions of differing velocity. According to Xernst, the 

 potential difference is produced by the more mobile ion 

 the H' ion of a dilute hydrochloric acid solution advancing 

 more rapidly than the Cl' ion, and thus conferring its charge on 

 the adjoining second electrolyte. When, for example, dilute 

 equivalent solutions of HC1 and NaCl are in contact, the so- 

 called diffusions potential at the interface is due only to the 

 different mobility of the H* and Na- ions. For this simplified 

 case, in which binary electro! :ng two univalent ions in 



equivalent concentration are considered, Nernst's theory gives 

 the following equation : 



in which K is the electromotive force, R the gas constant, T the 

 absolute temperature, F the quantity of electricity carried by 

 a univalent ion, % and 11% the mobilities of the cations, and r t 

 the mobility of the common anion. A case as simple as this is 

 difficult to realise in the salts of the albumins, as their dissocia- 

 tion is less than that of most salts, and would have to be 

 determined accurately in each individual case. A further 

 condition which deserves notice is as follows. According to all 

 experience, the proteins yield salts with protein ions of increasing 

 valency when increasing quantities of alkali or acid are added. 

 A uniform constitution in the protein salt is to be expected in 

 low concentrations of acid or of alkali when the soluble protein 

 salt shows the protein ion of lowest valency. Again when the 



