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



resistance, as well as the resistance of the same kind of the volta- 

 meter which forms part of the interpolar, by interposing rheostats 

 whose resistance expressed in platinum wire is 5000 to 6000 mil- 

 lims. These rheostats are fitted in a test-tube full of water and 

 placed in the sixth muffle of the calorimeter ; so that all the heat 

 transported and consumed outside the calorimeter might by ap- 

 proximation be considered to be merely consumed in the electro- 

 lysis of the body. 



A second mercury calorimeter measures the heat disengaged 

 in that part of the circuit placed outside the calorimeter which 

 contains the battery and the rheostat. For this purpose each of 

 the voltameters successively introduced into the voltaic circuit is 

 placed in one of the muffles. 



The first calorimeter estimates the heat which is borrowed 

 from the battery for electrolyzing the bodies. 



The second calorimeter indicates that amount of heat, thus 

 borrowed from the battery, which after being used for electrolysis 

 is restored by the elements set at liberty, when, immediately 

 after chemical separation, and in virtue of an essentially local 

 phenomenon, these elements become modified in passing from 

 the nascent state (in which they exist in compounds) into the 

 ordinary condition. 



It is clear that the investigation of the distribution of heat in 

 the voltaic circuit may require the use of a great number of ca- 

 lorimeters. 



I mention also that, excepting in the nature of the plates, the 

 voltameters, both in their shape and in their dimensions, and in 

 the distance of the plates, are just like the couples of the bat- 

 tery, and the electrolytes are employed in such conditions that 

 the same volume of water always contains quantities which are 

 chemically equivalent to the quantity of sulphuric acid contained 

 in the battery. 



In the calorimeter which already contains the battery and the 

 rheostat, and in the seventh muffle, the voltameter which forms 

 part of the interpolar can be placed. In this case one and the 

 same calorimeter contains the whole of the circuit. 



I had already previously attempted to transfer to the inter- 

 polar almost all the heat developed in a Smee's element, or in a 

 battery composed of two or more Smee's elements of equal size. 

 To obtain this result, I introduced into the interpolar, and out- 

 side the calorimeter which contains the pile, as much as 700 

 millims. of normal platinum wire coiled on the cylinder of a 

 rheostat specially arranged for this purpose. This resistance 

 enables us to neglect almost entirely the physical resistance of 

 the battery and of the interpolar arc which includes the boussole, 

 seeing that this resistance, expressed as a length of wire, is only 



