CHEMISTRY OF CLAYS. clay substance from the sand or quartz. The aiCtion upO'n im pure quartz of a dilute sO'lution of sodium hydrate 0'1' sodium carbonate, furnishes means fO'r separating the quartz from the amorphous silica. The action of sulfuric acid and the alkali has given rise to a method O'f analysis, which is knO'wn as rational