1826.] Sulpho-Naphthalic Acid. 185 



The heavier substance was a red crystalline solid, soft to 

 the nail like a mixture of wax and oil. Its specific gravity was 

 from 1*3 to 1*4, varying in different specimens; its taste sour, 

 bitter, and somewhat metallic. When heated in a tube, it 

 fused, forming, as before, a clear but deep red fluid. Further 

 heat decomposed it, naphthaline, sulphurous acid, charcoal, 

 &c. being produced. When heated in the air it burnt with 

 much flame. Exposed to air it attracted moisture rapidly, 

 became brown and damp upon the surface, and developed a 

 coat of naphthaline. It dissolved entirely in alcohol, forming 

 a brown solution. When rubbed in water a portion of naph- 

 thaline separated, amounting to 27 per cent., and a brown acid 

 solution was obtained. This was found by experiments to 

 contain a peculiar acid mixed with a little free sulphuric acid, 

 and it may conveniently 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, 

 forming a clear red fluid, from which by a continued heat 

 much colourless naphthaline sublimed, and a black acid sub- 

 stance 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 pecu- 

 liar 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 solu- 

 tion of a small quantity of the dry peculiar acid in naphthaline ; 

 and that the heavier substance was a 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 peculiar 

 acid. But reversing the proportions, no excess of naphthaline 

 was competent, at least in several hours, to cause the entire 



