Coccus, B.P. Cochineal.
Cochineal consists of the dried fecundated female insect, Coccus Cacti, Linn. (Order Hemiptera), reared on Nopalea coccinellifera, Salm-Dyck (N.O. Cactaceae), and other species of Nopalea. It is also official in the U.S.P. The insects are indigenous to Central America and Mexico, but the drug is now chiefly obtained from the Canary Islands. After fecundation, the insects develop an abundance of red colouring matter. They are then collected by brushing them off the plants, and killed by the fumes of burning charcoal or sulphur, or by stove heat or hot water, "silver-grain" cochineal resulting in the former case, whilst "black- grain" cochineal is obtained when heat is applied. The dried insects are about 5 millimetres long, oval in outline, flat or slightly concave on one side, and arched on the other. They are wrinkled transversely, nearly black ("black-grain") or greyish ("silver-grain") in colour, and brittle, readily yielding a dull, purplish powder. When macerated with water no insoluble powder should separate. Incinerated with free access of air, the drug should not yield more than 10 per cent. of ash (B.P. and U.S.P., 6 per cent). Cochineal is often artificially weighted with inorganic matter. In the case of the silver-grain variety, barium or lead carbonate or sulphate is used, while the black-grain variety in "faced" with black lead, ivory black, or manganese dioxide, or may contain very dark grains of magnetic sand containing iron. These adulterants are readily detected by soaking the drug in water, or by the abnormally high ash.
Constituents.—The chief constituent of cochineal is about 10 per cent. of carminic acid, obtainable in small red prismatic crystals, soluble in water, alcohol, and alkaline solutions. About 10 per cent. of fat and 2 per cent. of wax are also present, as well as albuminoids and inorganic matter. The fat consists almost entirely of free oleic, linoleic, and myristic acids.
Uses.—Cochineal is used principally as a colouring agent. A tincture of cochineal is prepared and sometimes used as an ingredient of cough mixtures, but it has no medicinal virtues. The brilliant red colouring matter of the cochineal insect is best seen as carmine and its preparations. Tincture of cochineal tends to form a cloudy mixture with water, owing to the presence of some fat, and solution of carmine gives a brighter tint. Preparations of cochineal are turned yellow by the mineral acids and become purple with alkalies. The colouring matter is often precipitated by the salts contained in hard tap-water, and distilled water only should be used for dilution.
- Glycerinum Cocci, B.P.C.—GLYCERIN OF COCHINEAL. 1 in 10.
- Useful for imparting a rich red colour to preparations in which the presence of alcohol is not desired. A similar preparation containing alcohol is Liquor Cocci.
- Liquor Cocci, B.P.C.—SOLUTION OF COCHINEAL. Syn.—Liquid Cochineal. 1 in 10.
- Used to colour mixtures, lotions, mouth washes, etc., and it is also employed in culinary operations. It imparts a rose-pink or crimson colour to neutral or alkaline liquids, and a scarlet colour to acid liquids. This solution mixes more readily, and imparts a more brilliant colour, than ordinary solutions of cochineal. If desired the alcohol may be replaced by glycerin (see Glycerinum Cocci).
- Tinctura Cocci, B.P.—TINCTURE OF COCHINEAL.
- Cochineal, in powder, 10; alcohol (4.5 per cent.), 100. Prepared by the maceration process. Tincture of cochineal is used chiefly as a colouring agent, and as an indicator in alkalimetry. It is rendered more miscible by the addition of about 10 per cent. of potassium citrate. Dose.—3 to 10 decimils (0.3 to 1.0 milliliters) (5 to 15 minims).