M. P. A. Favre's Electrolytic Investigations. 293 



VIII. 





Thermal units. 



S0 4 H + ZnO 



= 12304 



S0 4 H + FeO 



= 10872* 



S0 4 H + CdO 



= 14290 



S0 4 H + CuO 



= 8895 



S0 4 H + H0 



= 



we effect the thermal analysis of the sulphates of zinc, iron, cad- 

 mium, copper, and hydrogen, by combining their constituent 

 elements taken in the ordinary state, and we obtain the following 

 numbers : — 



Thermal units. 



IX. Oxidation of zinc and conversion of its oxide"! kaoq« 



into sulphate J 



Oxidation of iron „ „ 45975 



„ cadmium „ „ 43415 



„ copper „ „ 26950 



hydrogen „ „ 34462 



These numbers are each about 12000 thermal units less than 

 those of Table V. and of Table VI., with the exception of the 

 number for hydrogen in Table VI., from which the difference is 

 about 18000. 



When the voltameter in which the sulphates are decomposed 

 is placed inside the seventh muffle of the calorimeter in which is 

 the battery, instead of being quite outside and apart from it, the 

 following numbers are obtained : — 



X. Electrolysis of sulphate of copper . 26568 



„ „ hydrogen. 34204 



numbers which do not much differ from those in the preceding 

 Table (IX.), but which differ greatly from the numbers in 

 Table VI. which refer also to the electrolysis of sulphate of cop- 

 per and of sulphate of hydrogen. 



If, changing the conditions of the preceding experiment, the 

 voltameter, instead of being placed in the calorimeter in which 

 is the battery, is placed in an independent one, numbers are ob- 

 tained which explain the difference mentioned between the re- 

 sults of experiment VI. and those of experiments X. 



The following are the numbers : — 



Heat taken from the Heat restored to the 

 pile and indicated by calorimeter No. 2, which 

 the calorimeter No. 1, contains the voltameter, 

 which contains the by the elements of the 



pile and the rheostat. salts decomposed. 



XI. Electrolysisof sulphate of copper 38530 12445 



„ „ hydrogen 54235 20335 



In these experiments (XL) the heat disengaged in the volta- 



* Annates de Chimie et de Physique, vol. xxxvii. p. 405. 

 Phil Mag. S. 4. Vol. 35. No. 237. April 1868. X 



