ASSOCIATION OF LIQUIDS 59 



in which Q is the heat absorbed on solution of one kilogram- 

 molecule, C the concentration. 



This formula allows of a molecular weight determination 

 of the dissolved substance, by calculating L from the data 

 on solubility, and dividing by the observed heat of solution 

 per kilogram ; thus for succinic acid (C 4 H 6 O 4 ) the amounts 

 dissolved in 100 parts of water at o and 8-5 respectively 

 are 2-88 and 4-22 ; hence we get from 



A f _Q_ 



_ _ _ 



~- . = 



The heat of solution per kilogram is 55, and therefore the 

 molecular weight =124 (C 4 H 6 4 = 118). 



C. Besults. 



i. Simple Molecular Magnitude of Dissolved Bodies. 



Putting together the results of the numerous determina- 

 tions of the molecular weights of dissolved bodies, the 

 leading conclusion arrived at appears to be that the mole- 

 cular magnitude is usually that corresponding to the 

 simplest formula that answers to the quantitative composi- 

 tion, and the chemical relations of formation and transforma- 

 tion. This conclusion has helped not a little towards the 

 favourable reception of the theory of solutions, and to 

 the working out of the molecular weight methods based 

 on it. 



Larger molecules. Agreement ivith the results of gas 

 density measurements. In the first place, departures from 

 the simplest possible molecular formula are found in cases 

 in which the gas density indicates the same thing. The 

 molecular magnitude of the elements, already referred to, 

 may be mentioned in this regard. Most are diatomic : so 

 also are oxygen, nitrogen, and hydrogen in aqueous solution, 



