Heat confined 



Heat 



correspond in 



vithin the battery. 





to R+r. 



units. 





units. 



1816 





18018 



2349 





17485 



3373 





18461 



4777 





15057 



5410 





14424 



M. P. A. Favre's Thermal Researches on the Battery. 313 



Value of II. 



millims. 

 7000 

 4000 

 1000 



500 



250 



V. Resuming my determinations of the electrolysis of sulphate 

 of copper and sulphate of hydrogen*, and varying the conditions 

 of the experiments, I obtained a number higher than those I 

 have given, and which must be nearer the real number repre- 

 senting the change of condition of hydrogen. This number, 

 which is about 6000 thermal units, is but little different from 

 that given in my previous memoir. 



In the present series of researches I have taken the precaution 

 to collect and analyze the gases disengaged in the voltameter, 

 and to allow for the formation of oxygenated water and for the 

 water which is reformed. 



When, instead of working with pure and renewed acid, the pro- 

 portion of sulphate of zinc is allowed to increase, the influence 

 due to the electrolysis of the salt is soon evident. In conse- 

 quence of it a deposit of zinc is formed on the surface of the pla- 

 tinum. In dissolving, this produces a quantity of heat which is 

 not transmissible to the circuit — a fact which explains the num- 

 ber 9122 which expresses the quantity of heat which is not 

 found in the circuit R + r, and which the causes previously in- 

 vestigated would not have produced. 



VI. In fact, when we examine what takes place in a battery 

 of several Smee's elements, we see, when by successive operations 

 the liquid has become charged with sulphate of zinc, that one or 

 several of the couples scarcely disengage any gas-bubbles ; then 

 when the circuit is opened, the couples disengage more and 

 more rapidly the complement of gas, forming for each element 

 a total equal to that which had been disengaged by each couple 

 working regularly to the moment of opening the circuit. 



The same phenomenon is produced with a single couple, and 

 becomes markedly apparent; for the disengagement of gas is 

 seen to continue for a certain time after the circuit is opened, and 

 then suddenly to stopf. 



The quantity of sulphate of zinc thus decomposed, and the 

 acid of which being liberated attacks the zinc of the couple,, 

 always corresponds to an equivalent quantity of sulphuric acid 

 which does not come into play in the reaction ; so that for the 

 same intensity there is always the same amount of zinc attacked 



* Comptes Rendus, vol. lxvi. Feb. 10, 1868. 



t I may remark that, the circuit being open, the zinc may remain im- 

 mersed for a whole week without any gas being liberated. 



Phil. Mag. S. 4. Vol. 38. No. 255. Oct. 1869. V 



