Dr. Andrews's Report on the Heat of Combination. 515 



Mean. ...5121 4108 



I. 



Specific heat 0-8018 



Specific gravity 1-1724 



It may be not uninteresting to compare these numbers with those 

 deduced by calculation from the specific heats of the salts in the dry 

 state. The latter have been inade the subject of experiment by 

 Avogadro and Regnault, but their results do not agree well with 

 each other. I have adopted Regnault's numbers in my calculations. 



Solution. 



Nitrate of potash I. 

 » if •^■ 



Nitrate of soda 1. 



»> 5> 2. 



Chloride of sodium 1. 

 o 



It is obvious that the specific heat of the solution is, in every in- 

 stance, less than the mean of the specific heats of its component 

 parts, and that serious errors would be committed, if we should 

 attempt to calculate on this principle of the thermal values of solu- 

 tions which may be formed in the course of our experiments. 



I have made a short series of experiments on the quantities of 

 heat absorbed during the solution of nitrate of soda and of nitrate of 

 potash, when added in succe!?sive portions to the same liquid. The 

 results fully confirm those previously obtained by Graham, but as 

 the experiments were only preliminary trials to a more extended in- 

 vestigation, it is not necessary to describe them in detail. I may 

 briefiy state, that on dissolving 12-22 grammes of nitrate of soda in 

 250 grammes of water and repeating the experiment with each new 

 solution, till the water was nearly saturated, the following decre- 

 ments of temperature were found : — 



By the aid of the specific heats already determined, and knowing 

 the thermal value of the vessel in which the experiments were per- 

 formed (4*3 grms.), I have calculated for experiments 1,4 and 9 the 



