298 M. P. A. Favre's Electrolytic Investigations, 



The deflection of the needle of a tangent-compass, as well as 

 the duration of operation, may well show the quantity of che- 

 mical action produced in each couple in equal times ; but the 

 calorimeter alone can give the quantity of heat at work in the 

 element — a quantity which in the same time and for the same 

 deflection of the needle increases with the number of couples. 

 The use of several calorimeters, containing the battery and the 

 various parts of the interpolar, enables us to measure the distri- 

 bution in the circuit of the motive force developed in the battery, 

 and to assign their respective parts to the complicated reactions. 



If we admit that the tangent-compass measures the number 

 of electro dynamic vibrations in the voltaic circuit, we are led to 

 the conclusion that the calorimeter measures Hhe magnitude and 

 velocity of these vibrations. 



The compound metalloid radicals either decompose water in a 

 manner opposite to that of the alkaline metals, combining with 

 its hydrogen and thus reproducing the acid decomposed, or they 

 decompose into oxygen (which is liberated) and a body (such 

 as SO 3 for the radical SO 4 ) which combines with water and also 

 reproduces the decomposed acid. 



Knowing the heat of formation of dilute sulphuric acid, start- 

 ing from sulphur * , from the compound SO 3 , and the metal- 

 loid radical SO 4 , it is easy to calculate the heat of formation of 

 the two latter. 



In a Smee ; s couple placed in the calorimeter, a considerable 

 portion of the heat developed by the chemical action remains 

 imprisoned in the calorimeter, and cannot be expended in the 

 interpolar in producing useful work. This quantity of heat, 

 represented by about 6000 thermal units, and which remains 

 confined within the battery, is produced in the passage of hy- 

 drogen from the nascent to the ordinary state. 



We may make the same remark with regard to the battery 

 formed with Smee's elements — with this observation, that to 

 this first quantity of heat, necessarily lost as regards useful work, 

 a second must be added, which is accidentally lost in the couples 

 where it is produced, and where it is used in the partial electro- 

 trolysis of the sulphate of zinc formed there. 



The quantity of heat restricted to the battery, and which is 

 represented by about 6000 thermal units, would doubtless be 

 higher if the nascent hydrogen, in becoming ordinary hydrogen, 

 did not pass into the gaseous state. 



This quantity of heat, which it is impossible to transfer out- 

 side the element, cannot be attributed to the solution in water 



* Mechanical Researches on Compounds in Multiple Proportions (Thesis, 

 1853), and Journal de Pharmacie et de Chimie, 3rd ser. vol. xxiv. pp.241, 

 311 & 412 (1853). 



