410 Mr. Graham on the Meat disengaged in Combinations. 



In water of 0°* 6 3 R. 



In 1 equivalent of sulphuric acid, of 0, 94, 0°*96, 1°*02; 

 mean 0°*97 R. 



The mixture of an equivalent of sulphate of "mater, 30*68 

 grains, in 300 grains of water, with another 700 grains of water, 

 occasioned a rise of 0, 09 R. ; with 700 grains of water con- 

 taining 1 equivalent of hydrochloric acid a rise of o, 16, and 

 with 700 grains of water containing 1 equivalent of nitric acid, 

 0°'00. 



The magnesian sulphates generally resemble sulphate of 

 water in producing heat and not cold on dilution of their 

 strong solutions. The solutions of the three following salts 

 were saturated in the cold : — 



Sulphate of zinc (density 1*395), with equal bulk of water, 

 + 0°*60. 



Sulphate of magnesia (density 1*294), with equal bulk of 

 water, + 0°*60. 



Protosulphate of iron (density 1*227), with equal bulk of 

 water, + 0°*04. 



The experiments on the solution of salts in acids leave it 

 doubtful, whether the additional depression of temperature is 

 due in every case and entirely to a combination of the salt 

 with the acid, as it may be supposed to be when sulphate of 

 potash is dissolved in dilute sulphuric acid, bisulphate of pot- 

 ash being then formed, or whether it is a consequence of a 

 partial decomposition of the salt by the free acid to which it 

 is exposed. The small portion of acid, generally a single 

 equivalent, which produces the greatest proportional effect, 

 seems to indicate that combination or decomposition is the 

 cause, rather than any alteration in the solvent power of the 

 liquid. The action of hydrochloric acid and of nitric acid is 

 often the same, and is greater than that of sulphuric acid. 

 This appears even in the solution of a magnesian chloride in 

 water and in these acids. 



Thus 42*29 grains, 1 equivalent, of the fused anhydrous 

 chloride of zinc were dissolved in 1000 grains of water with a 

 rise in two experiments of 3°'42, 3°*45 R., of which the 

 mean is 3 0, 44 R. In 1000 grains of water containing 1 

 equivalent of sulphuric acid, with a rise of 3 0, 43, 3 a> 42, 

 3°*42 R., in three experiments ; which is nearly the same 

 result as in pure water. In the same quantity of water con- 

 taining 1 equivalent of hydrochloric acid, with a rise of 2°-86, 

 2°*88, 2°-86 ; of which the mean is 2°*87 R., being 0°*57 less 

 heat than in water alone. The presence of the hydrochloric 

 acid has therefore occasioned a fall of 0°*57 in the solution of 

 chloride of zinc, while the action of sulphuric acid is insensible. 



