Table 416. 

 ELECTROCHEMICAL EQUtVALENTS- 



345 



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

 tricity per unit change of valency. This constant is 96.494 coulombs or 26.804 ampere-hours per gram-hour (a Fara- 

 day) corresponding to an electrochemical equivalent for silver of 0.00111800 gram sec"' amp"*. It is to be noted that 

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

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

 equivalent" C|uantitie5 per unit time. The valence is then inciiided ia the "cbemicaily equivalent" quantity. The fol- 

 lowing table IS based on the atomic weights of 19x7. 



The electrochemical equivalent for silver is o.ooi 1 1800 g sec~i amp"'. (See p. xxrvii.) 



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 



(1913)- 



For a unit change of valency for the diatomic gases Bn, Cb, Ft, H5, Ni and Oj there are required 



8.619 coulombs/cm' 0° C, 76 cm (0.1160 cmVcoulomb) 

 2.394 ampere-hours//, 0° C, 76 cm (0.4177 //ampere-hour). 



Note. — The change of valency for Oj is usually 2, etc 

 SwiTHsoNiAN Tables- 



