. 814 



solution, whereas in passive state an oxygen charge counteracts the 

 solution. ^) 



About the way in which the oxygen retards the establishment of 

 the electromotive equilibrium, or the hydrogen accelerates it, few 

 special suppositions are found in the literature. It may, however, 

 be assumed that in general it is supposed that the establishment of 

 the heterogeneous equilibrium, metal-electrolyte is influenced by the 

 gas charge. 



The above-mentioned theories have all this in common, that in 

 passive state there exists no heterogeneous equilibrium between the 

 metal and the solution. On the other hand there are also 

 theories according to which there does exist heterogeneous equili- 

 brium between metal and electrolyte, but the internal equilibrium in 

 the electrolyte or in the metal is disturbed. 



Le Blanc '1 assumes, that the equilibrium between anhydrous and 

 hydrated ions in the solution sets in slowly. When in consequence 

 of anodic polarisation the concentration of the anhydrous ions at 

 the anode increases, these combine in some cases only slowly with 

 the water present. 



This increases the concentration of the anhydrous ions greatly, 

 though the total ion concentration increases only little. According 

 to Le Blanc the cause of passivity would, therefore, be a concen- 

 tration polarisation in the solution. Also Kurssner ') and Schildbach *) 

 see passivity in this way. 



The second possibility, that passivity is the result of an internal 

 change of the metal, has repeatedly been pronounced. Hittore ^) 

 speaks of a "Zwangzustand", without expressing an opinion as to 

 what it consists in. 



Also Byers ") thinks that passivity is owing to a particul^ir con- 

 dition of the metal, which is brought about "by a great number of 

 ditferent influences. 



FiNKELSTEiN ^) and W. J. Muller ^) assume that in passifiable 



') FoEKSTEE, Elektrochemie wassriger Lösungen, Leipzig 1915, 367. 

 s) Zeitschr. f. Elektrochemie 9, 636, (1903); 11, 705, (1905). Zeitschr. f. physik. 

 Chemie 46, 213 (1903) Boltzmann Festschrift 1904, 183, Chem. News. 109, 63, (1914). 

 3) Zeitschr. f. Elektrochemie 16, 754, (1910). 

 *) Ibid 16, 967, (1910). 

 6) Zeitschr. f. physik. Chemie 25, 729, (1898); 30, 481. (1899); 34, 91, (1902). 



6) Journ. Amer. Chem. Soc. 30, 1718, (1908); 32, 750, (1910) ; 33, 17 57, (1911) ; 

 34, 1368, (1912); 35, 759, (1913). 



7) Zeitschr. f. physik. Chemie 39, 91, (1902). 



«) Ibid. 48, 577. (1904); Zeitschr. f. Elektrochemie 15, 696, (1909). 



