in Comlustion, and in the Condensation of Vapours. 439 



§ VI. Heat developed in the Combustion of sulphuric Ether. 



I have already mentioned the difficulties which I over- 

 came before being able to regulate the combustion of this 

 substance in such a way as to render the results of iny ex- 

 periments regular and satisfactory; but I met with still 

 further difficulties in the course of this delicate inquiry. 



As alcohol is necessarily employed in making sulphuric 

 ether, and as these two liquids n)ay be united in any pro- 

 portions, it is extremely difficult, if not impossible, to se- 

 parate them entirely ; and as both are colourless and limpid, 

 either when mixed or separate, we can scarcely judge of 

 the degree of purity of the ether, except by its specific gra- 

 vity, and even in this way but very imperfectly. 



The most highly rectified sulphuric ether which I could 

 procure, and which I employed in my experiments, was 

 prepared in M. Vauquelin's laboratory. Its specific gravity 

 is 72834 at the temperature of I G" Reaumur. As that 

 which was employed by M. de Saussure in his analysis was 

 only of the specific gravity of 717 at the same tempera- 

 ture ; by regarding the ether which I employed as being a 

 mixture of the same degree of purity with that of M. de 

 Saussure, and the pure alcohol of Lowitz having a specific 

 gravity of 792, we shall find upon making a calculation, 

 that the ether which I employed was a mixture of 83 parts 

 of ether of the specific gravity of 717, and 13 parts of pure 

 alcohol of Lowitz of the specific gravity of 792. 



On burning this mixture under my calorimeter, after 

 having brought my apparatus to the highest degree of per- 

 fection, I obtained the following results : 



