during the Comhination of Acids and Bases. 243 



42. Thus the hydrocyanic acid developes with potash, soda, barytes, and 

 ammonia, 5° less than the other acids. On the other hand, it yields no less than 

 7°.l in combining with the peroxide of mercury, while the oxyacids produce 

 with the same base, only r.27. 



43. I now proceed to cite a few experiments in illustration of Law 2 ; viz., 

 that during the conversion of a neutral into an acid salt, no evolution of heat 

 occurs. 



44. 23 gr. of a solution of caustic potash, containing .353 gr. of alcali, were 

 mixed with 7 gr. of a solution of oxalic acid, containing .271 gr. (or 1 equiv.) of 

 acid. 



Temp, after mixture rose 5°.7. 



45. 31 gr. of a solution of neutral oxalate of potash, containing .624 gr. of 

 the salt, were mixed with 9 gr. of a solution of oxalic acid, containing .271 gr. 

 (1 equiv.) acid. 



Temp, after mixture rose 0°.0. 



46. The solution of binoxolate of potash, obtained in last experiment, was 

 mixed with 18 gr. of the solution of oxalic acid (2 equiv.) 



Temp, rose after mixture 0°.15. 



After some time, crystals of quadroxalate of potash began to form, which 

 accounted for the slight elevation of temperature. 



47. On adding to a solution of sulphate of potash a second atom of sulphuric 

 acid, the temperature of the mixture rose only 0°.l, although the combination of 

 the first atom had produced 6°.3 of heat. 



48. Similar results were obtained with the oxalate, tartrate, and acetate of 

 soda, when converted into the corresponding supersalts ; and by neutralizing 

 these acid salts with the base, the same heat was invariably produced as if the 

 excess of acid had existed in a free state. I may cite particularly the case of the 

 bichromate of potash, which gave, when converted into the neutral chromate, a 

 quantity of heat corresponding with that developed by the acids in general with 

 potash, viz., 6°.45. In verifying this principle, care must be taken to select 

 examples where all the compounds are soluble salts ; otherwise, the latent heat 

 extricated by the solid precipitate would interfere with, and complicate the 



2i 2 



