CARMIN′IC ACID

C 14 H 14 O 8 . Prep. (W. De la Rue.) The powdered insect, after treatment with ether to remove the fat, is digested in water. The decoction of cochineal is precipitated by adding a solution of acetate of lead, and the impure carminate of lead thus formed, after being washed with water, is suspended in water, and decomposed by a stream of sulphuretted hydrogen; the whole proce is repeated with the decanted solution so obtained; the second solution is then evaporated to dryne (in vacuo over sulphuric acid), di olved in absolute alcohol, digested on some washed crude carminate of lead (to separate a little phosphoric acid), and, lastly, mixed with ether (to precipitate some nitrogenised matter); the residuum obtained by careful evaporation (in vacuo) is pure carminic acid. Prop., . A purple-brown ma , yielding a rich-red powder; it is freely soluble in water and alcohol; slightly soluble in ether; and without decomposition in oil of vitriol; it is feebly acid; its salts are termed car min ates, only two or three of which have been examined. According to Mr De la Rue, this acid constitutes the pure colouring matter of cochineal.