186 On Sulphuric Acid and Naphthaline. [1826. 



disappearance of the sulphuric acid. When the experiment 

 was carefully made with pure naphthaline, and either at com- 

 mon 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 hydrocarbon. 



Hence it appears, that when concentrated sulphuric acid 

 and naphthaline are brought into contact at common or mode- 

 rately 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 conveniently be called the impure solid acid. The expe- 

 riments 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 solid acid, the water was 

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

 thaline present ; the latter separating in a colourless state from 

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

 acid diminished, crystallization in tufts commenced here and 

 there, and ultimately the whole became a brownish yellow solid. 

 A sufficient addition of water dissolved nearly the whole of this 

 hydrated acid, a few flakes only of naphthaline separating. 



A portion of the impure acid in solution was evaporated at 

 a moderate temperature; when concentrated, it gradually 

 assumed a light brown tint. In this state it became solid on 

 cooling, of the hardness of cheese, and was very deliquescent. 

 By further heat it melted, then fumed, charred, &c., and gave 

 evidence of the abundant presence of carbonaceous matter. 



Some of the impure acid in solution was neutralized by pot- 

 ash, during which no naphthaline or other substance separated. 

 The solution being concentrated until ready to yield a film on 

 its surface, was set aside whilst hot to crystallize : after some 

 hours the solution was filled with minute silky crystals, in 

 tufts, which gave the whole, when stirred, not the appearance 

 of mixed solid salt and liquid, but that of a very strong solution 

 of soap. The agitation also caused the sudden solidification 

 of so much more salt, that the whole became solid, and felt like 

 a piece of soft soap. The salt when dried had no resemblance 

 to sulphate of potash. When heated in the air, it burnt with 



