Page:Experimental researches in chemistry and.djvu/201

186 disappearance of the sulphuric acid. When the experiment was carefully made with pure naphtha line, and either at common or slightly elevated temperatures, no sulphurous acid appeared to be formed, and the action seemed to consist in's simple union of the concentrated acid and the hydrocarbon.

Hence it appears, that when concentrated sulphuric acid and naphtha line are brought into contact at common or mode-» rately elevated temperatures, a peculiar compound of sulphuric acid with the elements of the naphtha line 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 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 solid acid, the water was taken up to the exclusion of nearly the whole of the free nephthaline 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 Hakes only of naphtha line 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 potash, during which no naphtha line or other substance separated. The solution being concentrated until ready to yield a film on its surface, was set aside whilst hot to crystalline: 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