Heat evolved in Chemical Combination. 183 



suits of Dulong, as given in page 22, with Berzelius's remarks, 

 are directly opposed to this idea. 



In connexion with the subject of this abstract we have to 

 notice a paper by Dr. Andrews of Belfast, < On the Heat de- 

 veloped during the Combination of Acids and Bases/ read be- 

 fore the Royal Irish Academy, January 11, 1841*. 



The general conclusions at which the author arrives are 

 contained in the two following laws : — 



Law 1. The heat developed during the union of acids 

 and bases is determined by the base, and not by the acid ; the 

 same base producing, when combined with an equivalent of 

 different acids, nearly the same quantity of heat, but different 

 bases a different quantity. 



Law 2. When a neutral is converted into an acid salt, no 

 change of temperature occurs. 



In the commencement of the pap*er 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 alkaline, 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 gramme of pure 

 alkali, 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 

 show, 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 cir- 

 cumstances with the arsenic, phosphoric, nitric, boracic, hydro- 

 chloric, hydriodic and oxalic acids, the elevations of tempera- 

 ture, indicated by the thermometer, vary only from 6'8° to 

 6'6°. Sulphuric acid produces rather a higher temperature 

 than any other acid (7*3°), and the acetic, formic, tartaric, 

 citric, and succinic acids, give rather less heat than those be- 

 fore mentioned (from 6*4° to 6*1°). In like manner, ammonia 

 produces an increase of temperature varying from 5*7° to 5'5°, 

 when neutralized by the nitric, hydrochloric, hydriodic, arse- 

 nic, 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 suc- 

 cinic acids (5*1°). Analogous results are described as having 



* From the Proceedings of the Royal Irish Academy : the paper will 

 appear in vol. xix. Part II. of the Transactions of the Academy. 



