Mr. Graham on the Heat disengaged in Combinations. 4-07 



The high solubility of the nitrate of soda adapts it for si- 

 milar experiments. It will be observed that a difference of 

 13 degrees of temperature does not materially affect the 

 amount of heat absorbed on dissolving a single equivalent of 

 this salt. The capacity for heat of the crystallized salt is 

 0-278 (Regnault). 



One equivalent of nitrate of soda, 53*40 grains, dissolved in 

 100 grammes of water: — 



Before solution . . 65°-07 51°'78 51°*63 

 After solution . . . 61°-56 48°*25 48°*08 



Fall 3°-51 3°-53 3°'55 



Ten equivalents of this salt being dissolved successively in 

 the same 100 grammes of water, the following changes of 

 temperature were observed : — 



Fall 



Fall . 2°-39 2°-29 2°'15 1°'98 1°*88 



The solution of the tenth equivalent of this salt produces 

 therefore only one-half the cold due to the first equivalent. 



The solution of chloride of potassium in water is attended 

 with a fall of temperature, which is considerable, although not 

 so great as with nitrate of potash. 



One equivalent of chloride of potassium (46*62 grains) dis- 

 solved in 100 grammes of water : — 

 Before solution . . 62°-05 61°'80 61°*70 

 After solution . . . 59°* 10 58°*88 58°*75 

 Fall of temperature . 2°*95 2°*92 2°-95 Mean 2°*94. 



At a lower temperature : — 

 Before solution . . 45°*55 45°*04 45°'S3 

 After solution . . . 42°*55 42°*02 42°*50 

 Fall of temperature . 3°*00 3°*02 3°*03 Mean 3°*02. 

 II. Neutralization of Hydrate of Potash by Sulphuric Acid. 



Half an equivalent of sulphuric acid, 12*53 grains, was sa- 

 turated with a slight excess of hydrate of potash, the united 

 liquids containing 100 grammes of water, as in the preceding 

 experiments with nitric and hydrochloric acids : — 

 Before mixture . . 61°*31 61°*45 61°\53 

 After mixture . . . 67°*01 67°*13 67°*21 

 Rise 5°-70 5°*68 5°*68 Mean 5°*69. 



