VII. 



ELECTROCHEMICAL THERMODYNAMICS. 



Two letters to the Secretary of the Electrolysis Committee of the 

 British Association for the Advancement of Science. 



[Report Brit. Asso. Adv. Sci, 1886, pp. 388, 389 ; and 1888, pp. 343-346.] 



New Haven, Janua/ry 8, 1887. 

 Professor OLIVER J. LODGE, 



Dear Sir, Please accept my thanks for the proof copy of your 

 " Report on Electrolysis in its Physical and Chemical Bearings," which 

 I received a few days ago with the invitation, as I understand it, to 

 comment thereon. 



I do not know that I have anything to say on the subjects more 

 specifically discussed in this report, but I hope I shall not do violence 

 to the spirit of your kind invitation or too much presume on your 

 patience if I shall say a few words on that part of the general subject 

 which you discussed with great clearness in your last report on 

 pages 745 ff. (Aberdeen). To be more readily understood, I shall 

 use your notation and terminology, and consider the most simple case 

 possible. 



Suppose that two radicles unite in a galvanic cell during the 

 passage of a unit of electricity, and suppose that the same quantities 

 of the radicles would give Oe units of heat in uniting directly, that is, 

 without production of current ; will the union of the radicles in the 

 galvanic cell give J0e units of electrical work ? Certainly not, unless 

 the radicles can produce the heat at an infinitely high temperature, 

 which is not, so far as we know, the usual case. Suppose the highest 

 temperature at which the heat can be produced is t", so that at this 

 temperature the union of the radicles with evolution of heat is a 

 reversible process; and let t' be the temperature of the cell, both 



temperatures being measured on the absolute scale. Now Oe units 



j.' 



of heat at the temperature t" are equivalent to #6777 units of heat at 



I/ 



A/r j.t 



the temperature t' t together with J0e -77- units of mechanical or 



t 



electrical work. (I use the term "equivalent" strictly to denote 



