204 Mr, farailay on the Mutual Action of SulphuncAcul [Sept. 



obtained. This was found by experiments to contain a peculiar 

 acid mixed with a httle free sulphuric acid, and it may conve- 

 niently be called the impure acid. 



The lighter substance was much harder than the former, and 

 more distinctly crystalline. It was of a dull-red colour, easily 

 broken down in a mortar, the powder being nearly white, and 

 adhesive like naphthaline. It was highly sapid, being acid, 

 bitter, and astringent. When heated in a tube it melted, form- 

 ing a clear red fluid, from which, by a continued heat, much 

 colourless naphthaline sublimed, and a black acid substance 

 was left, which at a high temperature gave sulphurous 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, contaminated with very little 

 sulphuric acid. More minute examination proved that this 

 lighter substance, in its fluid state, was a solution of a small quan- 

 tity of the dry peculiar acid in naphthaUne ; 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 moderately 

 elevated temperatures, a peculiar compound of sulphuric acid 

 with the elements of the naphthaline is produced, which possesses 

 acid properties; and as this exists in large quantity in the 

 heavier of the bodies above described, that product may conve- 

 niently be called the impure solid acid. The experiments made 

 with it, and the mode of obtaining the pure acid from it, are 

 now to be described. 



Upon applying heat and agitation to a mixture of one volume 

 of water, and five volumes of impure soHd acid, the water was 

 taken up to the exclusion of nearly the whole of the free naph- 

 thahne present : the latter separatmg in a colourless state from 

 the red hydrated acid beneath it. As the temperature of the 

 ^cid diminished, crystallization in tufts commenced here and 



