A History of Hindu Chemistry from the Earliest Times to the Middle of the Sixteenth Century A.D. v1.c18.s4.4

v1.c18.s4.4

In the place of this rather clumsy mode of cleansing, which is largely practised even in the metropolis, some of the more adventurous rungwalas use a rather more clever and neater method. Instead of preparing a large amount of tamarind pulp, they obtain from the grocer's an ounce or two of a dull white crystalline substance which they call "acid," and a solution of this serves equally well, if not better, for their purpose. To the question as to what the substance called "acid is, they cannot give a satisfactory reply. And even the grocer who sells it cannot enlighten the inquirer more than to this extent that the article is a *gād* (scum) or a bye-product in the manufacture of some acid. Having subjected the substance to a rough chemical analysis, we came to to conclusion that the substance should be nothing more nor less than KHSO₄ or hydric potassic sulphate, an acid salt and a bye-product, as we know, in the process of manufacturing nitric acid. The reaction of this substance on the copper seems to be this:— 2 KHSO₄ + CuO = K₂SO₄ + CuSO₄ + H₂O.