RICHARDS. SOURCE OF CHEMICAL HEAT. 



401 



would apply equally in each case ; hence in the first approximation the 

 usual values for the heats of combination may be given without affecting 

 the argument. 



The table of data herewith collected compares the contraction which 

 takes place when two gram-atoms of chlorine combine with some other 

 substance, and the heat evolved during the operation. 



Comparison of Contraction with Heat of Formation involved in 

 the Synthesis of Chlorides. 



The parallelism of the heat of reaction and the contraction which 

 results from it, is obvious from the table and the accompanying diagram, 

 vol. xxx vii. — 26 



