Mr. Graham on the Heat disengaged in Combinations. 409 



which dissolves in 1000 grains of water with a fall of o, 88 R. 

 (Chemical Memoirs, vol. i. p. Ill), dissolved in the same 

 quantity of water already containing an equivalent of sulphuric 

 acid with a fall of 1°-12, 1°*17, 1°*18 R. in three experiments; 

 of which the mean is ]°'16, being o, 28 more than in pure 

 water. A second equivalent of crystallized sulphate of mag- 

 nesia, when dissolved in the same liquor, produced a fall, in 

 three experiments, of 0°*96, 0°«92, 0°'95 R., of which the 

 mean is o, 94, or only o, 06 more than in pure water. 



In an equivalent of nitric or of hydrochloric acid, the fall 

 from the solution of an equivalent of crystallized sulphate of 

 magnesia was nearly double what it is in pure water. 



The fall in water containing 1 equivalent of nitric acid was 

 1°-T0, 1°-G8, l°-64, of which the mean is 1°67. 



The fall in water containing 1 equivalent of hydrochloric 

 acid was 1°"70, 1°*70, 1°'68; mean 1 0< 69 R. 



The fall on the solution of 1 equivalent of sulphate of 

 magnesia in ^ equivalent of hydrochloric acid was 1 0, 37, 

 l°-37, 1°*38; mean 1°\37 R. The excess of cold produced 

 by the half equivalent of this acid, over water alone, was 

 therefore o, 50 ; the excess by the whole equivalent of acid 

 o, 82 ; so that fully more than one-half of the effect is pro- 

 duced by the first half equivalent of acid. 



An excess above 1 equivalent of acid to 1 equivalent of a 

 salt of this class increases the depression of temperature still 

 further, but in a less degree than the direct proportion of its 

 quantity. Thus the cold on dissolving 1 equivalent of sul- 

 phate of zinc in water being l c, 02 R., — 



In H equivalent of sulphuric acid, l°-22, 1°-19, 1°*25 ; 

 mean l°-22. 



In 1 equivalent of nitric acid, 1 0, 56, 1°'55,1°'54; mean \°'55. 



In i equivalent of hydrochloric acid, l°-50, 1°*50, 1°*47; 

 mean 1°*49. 



In 1 equivalent of hydrochloric acid, l°-82, 1°83, l°-86 ; 

 mean l°-83. 



In 2 equivalents of hydrochloric acid, 2°-26, 2°-26, 2°*24 ; 

 mean 2°'25. 



The solution of an equivalent of crystallized sulphate of iron 

 was attended with a fall of temperature, — 



In water of l°-06 R. 



In 1 equivalent of sulphuric acid, of 1°'28, l°-20, l°-26, 

 l°-25 ; mean l°-25. 



In 1 equivalent of hydrochloric acid, of 1°'69, l°-68, 1°*73 ; 

 mean 1*°70. 



The solution of an equivalent of crystallized sulphate of 

 copper was attended with a fall of temperature, — 



