INDUSTRIAL ELECTRO-CHEMISTRY 141 



the economical working of an electrochemical process, in 

 exactly the same way as it is for electric lighting, traction, 

 and power purposes in general. Before the advent of the 

 dj^namo, the primary battery was the only available source of 

 the electric current, if we except a limited use of the thermo- 

 pile, and its limitations are obvious. The operation of a 

 primary cell meant and still means essentially oxidation of 

 zinc. When zinc changes from the metallic state into biva- 

 lent ions, 1.22 grams are oxidized, according to Faraday's 

 law, for every ampere hour; we know that, with all possilDle 

 combinations of zinc with other materials in a primary bat- 

 tery, we never get much more than 2 volts, and if we assume 

 the useful e.m.f. to be 1 volt (which is very fair for such an 

 estimate), then every kilowatt hour produced means the oxi- 

 dation of 1.22 kg (or 2 J pounds) of zinc. This is the theo- 

 retical value which really represents a minimum of actual 

 consumption; moreover, it does not include the cost of the 

 other materials in the cell, nor the cost of construction and 

 attendance; but it is sufficient to indicate the inherent limi- 

 tations of the zinc primary battery. 



So long as primary cells were the only commercial sources 

 of electric current, the applications of electrical engineering 

 were thus necessarily restricted to those cases in which a very 

 small amount of power only is required. That is especially 

 the case in telegraph}^, and, in the field of electrochemistry, 

 in those cases of electroplating in which a soluble anode is 

 used of the same metal which is to be deposited upon the 

 cathode. Here the voltage required at the terminals of the 

 plating bath is consumed in overcoming the internal resist- 

 ance only, w^hich may be made small, and, therefore, the 

 power may also be insignificant. 



It is quite natural that after the dynamo had made its 

 commercial appearance, electric lighting and the mechanical 

 applications of electricity, such as traction and power trans- 

 mission and distribution, first attracted the inventive talents 

 of electrical engineers. Nevertheless, as we were reminded 

 by the institute dinner to Mr. Edison, the incandescent 

 lamp is now only 26 years old. It is, therefore, not surprising 

 that our electrocbemjcal industries are still young, since their 



