144 Mr. Faraday on the mutual action of 



heat much colourless naphthaline sublimed, and a black acid 

 substance was left, which at a high temperature gave sul- 

 phurous acid and charcoal. "When heated in the air it took 

 fire and burnt like naphthaline. Being rubbed in a mortar 

 with water, a very large portion of it proved to be insoluble ;^ 

 this was naphthaline ; and on filtration the solution contained 

 the peculiar acid found to exist in the heavier substance , con- 

 taminated with very little sulphuric acid. More minute 

 examination proved that this lighter substance in its fluid state 

 was a solution of a small quantity of the dry peculiar acid in 

 naphthaline ; and that the heavier substance was an union of 

 the peculiar acid in large quantity with water, free sulphuric 

 acid, and naphthaline. 



It was easy by diminishing the proportion of naphthaline 

 to make the whole of it soluble, so that when water was 

 added to the first result of the experiment, nothing separated; 

 and the solution was found to contain sulphuric acid with 

 the pecuhar acid. But reversing the proportions, no excess 

 of naphthaline was competent, at least in several hours, to 

 cause the entire disappearance of the sulphuric acid. When 

 the experiment was carefully made with pure naphthaline, 

 and either at common, or slightly elevated temperatures, no 

 sulphurous acid appeared to be formed, and the action seemed 

 to consist in a simple union of the concentrated acid and the 

 hydro-carbon. 



Hence it appears, that when concentrated sulphuric acid 

 and naphthaline are brought into contact at common, or mo- 

 derately elevated temperatures, a peculiar compound of sul- 

 phuric acid with the elements of the naphthaline is produced, 

 which possesses acid properties ; and as this exists in large 



