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IX. On the Heat developed during the Combination of Acids and Bases. By 

 Thomas Andrews, M. D., M. R. I. A., Professor of Chemistry in the Royal 

 Belfast Institution. 



Read 11th January, 1841. 



1. IT has been long known that chemical actions are in general accompanied 

 by the evolution or abstraction of caloric. In most cases the change of tempera- 

 ture depends upon the result of the action of different causes, some of which 

 tend to increase, and others to diminish the initial temperature of the reacting 

 bodies. Thus, in the decomposition of a solution of carbonate of soda by con- 

 centrated sulphuric acid, the combination of the sulphuric acid with water and 

 with the alcali are two distinct sources of heat, while the separation of the 

 carbonic acid from the soda, and its evolution in the gaseous form, are equally 

 distinct causes of a diminution of temperature. To estimate the influence of 

 each of these circumstances in any particular instance is a problem of great 

 difficulty ; and we can only expect to accomplish its complete solution, by 

 confining our investigations, in the first place, to these simpler cases, where the 

 variations of temperature are produced by the operation of one single cause. 

 For this reason, I have confined myself, in this preliminary inquiry, to the 

 examination of the calorific phenomena which occur during the combination of 

 acids and bases with each other, under the most favourable circumstances, for 

 obtaining results free from complication. 



2. The experiments to be hereafter described were all performed with very 

 dilute solutions, by which means no correction was required for the heat evolved, 

 when strong solutions of certain acids and alcalies are diluted. The method of 

 operating is easily described. In separate glass vessels solutions of determinate 

 weights were prepared, one containing the quantity of alcali whose power of 

 generating heat was sought, and the other, a little more than the equivalent of 



