TABLE 416. 

 ELECTROCHEMICAL EQUIVALENTS- 



345 



Every gram-ion involved in an electrolytic change requires the same number of coulombs or ampere-hours of elec- 

 tricity per unit change of valency. This constant is 96.404 coulombs or 26.804 ampere-hours per gram-hour (a Fara- 

 day) corresponding to an electrochemical equivalent for silver of o.ooi 11800 gram sec" 1 amp" 1 . It is to be noted that 

 the change of valence of the element from its state before to that after the electrolytic action should be considered. 

 The valence of a free, uncombined element is to be considered as o. The same current will electrolyze "chemically 

 equivalent" quantities per unit time. The valence is then included in the "chemically equivalent" quantity. The fol- 

 lowing table is based on the atomic weights of 1917. 



The electrochemical equivalent for silver is p.ooi 11800 g sec" 1 amp" 1 . (See p. xxxvii.) 



For other elements the electrochemical equivalent = (atomic weight divided by change oi valency) times 1/96494 

 g/sec/amp. or g/coulomb. The equivalent for iodine has been determined at the Bureau of Standards as 0.0013150 



For a unit change of valency for the diatomic gases Brs, Cb, Fz, Hj, Nz and Oz there are required 

 8.619 coulombs/cm 3 o C, 76 cm (0.1160 cm 3 /coulomb) 

 2.394 ampere-hours//, o C, 76 cm (0.4177 //ampere-hour). 



NOTE. The change of valency for Oa is usually 2, etc. 

 SMITHSONIAN TABLES. 



