438 Prof. E. Edlund on the Thermal Phenomena of the 



sentations, No. 1 or No. 2, deserves to be preferred, we obtain 

 the best clue from the experiments instituted in order to mea- 

 sure the heat-phenomena in a chemical-decomposition cell or 

 voltameter. With this view Raoult employed partly water 

 acidulated with sulphuric acid, and partly a solution of sul- 

 phate of copper as electrolytic liquid , and with the help of a 

 mercury calorimeter measured the quantity of heat which arose 

 in the decomposition-cell over and above the quantity occa- 

 sioned there by the passage of the current in consequence of 

 the resistance*. If W is the total heat developed in the vol- 

 tameter, and gw (as before) the heat which the passage of the 

 current occasions in consequence of the resistance (or the gal- 

 vanic heat), W—gw was measured. This heat-difference, 

 which Raoult calls the local heat, may in the following be de- 

 noted by L. By special experiments Raoult moreover mea- 

 sured the polarization-electromotive force produced in the 

 voltameter during the passage of the current. This electro- 

 motive force may be denoted by e, and that of an element of the 

 Daniell pile by d. The series employed consisted, in the dif- 

 ferent experiments, of from two to twelve Daniell elements. 

 The numbers cited below under L denote the number of heat- 

 units which were developed in the voltameter during the libe- 

 ration of one equivalent of hydrogen or copper. As, more- 

 over, it cannot be necessary to describe more closely the 

 arrangements in the experiments, we may here add only that, 

 with the decomposition of the sulphuric-acid water, the two 

 poles in the voltameter consisted of platinum wires in the first 

 two experiments (A and B) — while in the third experiment 

 (0) only the positive pole consisted of platinum, the negative 

 being formed of a thick wire of copper. In all three experi- 

 ments with the copper solution the positive pole consisted of a 

 thick wire of platinum, and the negative of one of copper. 

 As may readily be understood, the voltameter alone was en- 

 closed in the calorimeter, and the piles stood outside of it. 

 The following were the results obtained : — 



On the decomposition of the water. 



T 



A. 2-04 +14898 



B. 1-75 + 7596 



C. 2-16 +17626 



From this we see that in both cases a considerably greater 

 * Ann. de Cfiim. ct dc Phys. [4] t. iv. p. 41 1 : see also t. ii. p. 317. 



On the decon 

 f the sulphate 



iposition 

 of copper. 



e 

 T 



L. 



A. 1-59 



B. 1-58 



C. 1-36 



+ 7594 

 + 7997 



+ 2821 



