432 Prof* E. Edlund on the Thermal Phenomena of the 



to that which is consumed by the electromotive force. In 

 other respects the two views lead to divergent results : for 

 example, according to one view the quantity of the primary 

 chemical heat is equal to that of the galvanic, wherefore the 

 former also gives a measure of the electromotive force ; ac- 

 cording to the other these two quantities may be different, 

 and consequently the primary chemical heat cannot serve as 

 a measure for the electromotive force, &c. 



In order to determine which of these two views accords 

 best with experience, we will more closely consider the expe- 

 riments which have been instituted for the purpose of studying 

 the thermal phenomena of the pile and of the current. For 

 brevity, we will name the first-cited method of consideration 

 No 1, and that proposed by me No. 2. 



3. Favre * has endeavoured, by direct experiments, to 

 answer the question, Is the whole of the galvanic heat which 

 arises in the circuit derived merely from that which is gene- 

 rated by the chemical processes ? For this he made use of a 

 mercury calorimeter with two muffles situated close to one 

 another, of the same nature as the calorimeter which Favre 

 and Silbermann had previously employed in their determina- 

 tions of the heat developed in chemical processes. The pile 

 he used consisted of a glass tube filled with water containing 

 sulphuric acid, in which were placed the two pole-plates, 

 amalgamated zinc and platinized copper (Smee's pile). It 

 was closed with a fine platinum wire, which was of unequal 

 length and thickness in different experiments. The hydrogen 

 evolved in the pile was collected and measured. The experi- 

 ment was first made in this way : — The pile was enclosed in 

 one muffle, and the platinum wire in the other ; at the same 

 time it must be remarked that the copper wires connecting 

 the pole-plates with the ends of the platinum wire, and 

 which were outside of the calorimeter, were so thick that 

 no perceptible development of heat could take place in 

 them. When, therefore, the experiment was thus arranged, 

 the calorimeter indicated the total sum of the heat which 

 was developed in the pile and the entire circuit while 

 the current was in action ; and since the quantity of the 

 hydrogen gas developed was at the same time known, it 

 was easy to calculate what the sum of the heat would have 

 been if the experiment had been continued until one equiva- 

 lent of zinc in the pile was dissolved. Thereupon the experi- 

 ment was varied by leaving the platinum wire outside of the 

 calorimeter, in consequence of which the galvanic heat which 

 arose in the wire had no effect upon the calorimeter. The 

 * Annates de Chimie et de Phijsique, (2) t. xl. p. 293 (1854). 



