during the Combination of Acids and Bases. 231 



8. The strongest nitric acid employed in these experiments contained 13.3 

 per cent, of real acid, and when one part of such an acid is diluted with nine 

 parts of water, no sensible production of heat can be discovered by the most 

 delicate thermometer. The corresponding solution of caustic potash, containing 

 only 1.3 per cent, of alcali, was of course far beyond the limit of such sources 

 of heat. That simple dilution exercised no influence on the result was further 

 proved, by increasing the weight of the acid liquid, and diminishing that of the 

 alcaline, while, at the same time, the quantities of acid and alcali in each, as also 

 the total weight of both liquids, remained the same ; yet such variations in the 

 form of the experiment produced no change whatever in the elevation of tem- 

 perature observed on mixing them. 



9. Having discussed the corrections arising from the form of apparatus, I 

 now proceed to give the details of the fundamental experiment, on the absolute 

 amount of heat evolved in the union of nitric acid and potash. The general 

 accuracy of these results was tested and confirmed by repeating the experiments 

 in the form of a series, in which (the weight of the whole liquid remaining 

 constant) the quantities of the combining substances were taken successively, in 

 the proportions expressed by the numbers 1, 2, 4 ; and it will be seen that 

 the corresponding increments of temperature bear a similar ratio to each 

 other. 



10. Into the brass vessel before described, a solution of caustic potash, con- 

 taining .0882 gr. of alcali was introduced. It weighed 27.3 gr., which, added 

 to 1.09 gr., the equivalent in water of the vessel and thermometer (6), makes 

 the whole equal to 28.39 gr. water. The acid solution, in a small glass tube, 

 weighed 2.83 gr., and contained .106 anhydrous nitric acid. Thermometer in 

 air stood at 38° F. 



Temp, of acid, .... 



J, alcaline solution, 



Mean temp, before mixture, 

 Temp, after mixture. 



Increase in temp. (31.22 water) . r.64 



11. The last experiment repeated. Ther. in air 39°. 



