Chapter II. 



Elementary Theory of the Conduction Process in 

 Electrolytes. 



1. Material Effects Accompanying the Conduction Process. That 

 material effects accompany the passage of the current through a non- 

 metallic medium was known at an early date. Thus Nicholson and 

 Carlisle * observed the decomposition of water, and Sir Humphrey Davy 2 

 isolated the element potassium by electrolysis of the hydroxide. While 

 it was thus recognized that chemical action is intimately associated with 

 the passage of the current through an electrolyte, the quantitative rela- 

 tionships were not studied until Faraday carried out his classical re- 

 searches. It is unnecessary to give here in detail the results of Faraday's 

 investigations. It will be sufficient to state the laws which now bear his 

 name; namely, that chemical action accompanying the passage of the 

 current is proportional to the quantity of electricity passing, and that, 

 for a given quantity of electricity, the chemical effects in the case of 

 different reactions are equivalent. These laws have since been verified 

 by a multitude of observations on the action of the current passing 

 through electrolytes. The most exact measurements have been made 

 on the deposition of silver and on the liberation of iodine. 3 In all cases, 

 Faraday's Law has been found to hold within the limits of experimental 

 error. It has been found to hold in the case of fused salts at higher tem- 

 peratures, 4 as well as in that of certain solid electrolytes. 5 



There are cases, indeed, where apparent exceptions to Faraday's Law 

 appear. For example, when a current is passed through a solution con- 

 taining a compound of sodium and lead in equilibrium with metallic 

 lead, there are deposited on the anode 2.25 equivalents of lead per equiva- 

 lent of electricity. 6 Similar results have been obtained in the case of 

 solutions of certain other metallic complexes in liquid ammonia. 7 These 

 cases, however, do not constitute an exception to Faraday's Law, since 

 there are present in these solutions, presumably, a series of complexes 



1 Nicholson and Carlisle, Nicholson's Jour. 4, 179 (1800) ; Gilbert's Ann. 6 340 (1800) 



'Phil. Trans. 100, 1 (1808). 



1 Bates and Vinal, J. Am. Chem. Soc. 36, 936 (1914). 



* Richards and Stull, Proc. Am. Acad. S8, 409 (1902). 



"Tubandt and Lorenz, Ztschr. f. phys. Chem. 87, 513 (1914). 



Smyth, J. Am. Chem. Soc. 39, 1299 (1917). 



7 Peck, J. Am. Chem. Soc. 1,0, 335 (1918). 



19 



