47 



Law 2. " When a neutral is converted into an acid salt, 

 no change of temperature occurs." 



In the commencement of the paper a preliminary experi- 

 ment is described, the object of which is, to determine the ex- 

 act quantity of heat evolved during the combination of nitric 

 acid and potash. The solutions, both acid and alkahne, were 

 taken so weak in this and all the other experiments detailed 

 in the communication, that subsequent dilution with water did 

 not produce any change of temperature. On neutralizing the 

 solution of caustic potash, containing 0"353 grammes of pure 

 alcali, with nitric acid, the temperature of the resulting solu- 

 tion of nitrate of potash, whose weight amounted to 30 gr., 

 was found (after all corrections had been made) to rise 6'75°,F. 



To illustrate law first, the author adduces tables which 

 shew, at a glance, the heat produced when an equivalent of 

 each base is neutralized by different acids. Thus, when the 

 same proportion of pure potash is combined under similar 

 circumstances with the arsenic, phosphoric, nitric, boracic, 

 hydrochloric, hydriodic, and oxalic acids, the elevations of 

 temperature, indicated by the thermometer, vary only 

 from 6*8° to 66°. Sulphuric acid produces rather a 

 higher temperature than any other acid (7'3°), and the 

 acetic, formic, tartaric, citric, and succinic acids, give ra- 

 ther less heat than those before mentioned (from 6-4° to Q'\°) 

 In like manner, ammonia produces an increase of tempera, 

 ture varying from 5-7° to 5*5°, when neutralized by the nitric, 

 hydrochloric, hydriodic, arsenic, oxalic, and acetic acids ; 

 the greatest divergence from these numbers occurring, on the 

 one hand, with the sulphuric acid (6-3°), and on the other, 

 with the citric, tartaric, and succinic acids (5*1°). Analoo-ous 

 results are described as having been obtained with other 

 bases, such as soda, barytes, magnesia, lime, and the oxides 

 of zinc and lead. On the contrary, the heat developed by 

 each base is peculiar to itself; and, consequently, the same 

 acid gives different elevations of temperature, with equiva- 



