Scientific American 8, 21.8.1869
In the provinces of Oaxaca, and Guaxaca, and other parts of Mexico, grows in greater profusion than anywhere else, the species of cactus called the Cactus opuntia or nopal, otherwise the Opuntia cochinillifera, one of the most important plants grown in that country. This plant is the home and pasture of a species of shield louse, and insect the properties of which have been known since the earlier part of the 16th centiry. It exists wild in the woods, or upon cultivated tracks of the Cactus opuntia, grown to afforda support for an insect the scientific name of which is Coccus, and the commercial name of which is cochineal. This insect furnishes a coloring matter of great importance in the arts, not excluding the fine art of painting in oils or water colors on canvas, drawing paper, or the cheeks of haggard belles, whose natural color has suffered damage from late hours, hot drinks, and pickle diet.
The little parasite, whose favorite home we have mentioned, furnishes the chief staple for these artificial blushes, or perhaps we should say blush, as it is, like the American Union, and unlike the beautiful tint which nature provides the young who do not defy her laws - "one and inseparable."
The cultivated insect furnishes the finest cochineal, but the wild, is less expensive to procure, and is therefore largely used. The insect as found in his native home, is shaped very much like a miniature turtle, its back being of an oval, shieldlike form, and its belly fist. It has on its back a rather deep furrow running longitudinally, and cross furrows, which unite with the main central furrow. Only the female insect affords the coloring principle for which these insects are sought. The male has wings of which the female is destitute.
We remember seeing in a geography book, in our youth, a picture of people gathering cochineal, which, although we have since seen it repeated, gives a wholly erroneous idea of the operation. In this mendacious illustration the people were represented as shaking and pounding with poles a tree, very much resembling an old fashioned red-cherry tree, having sheets of cloth spread upon the ground to catch the cloud of insects which were represented as falling to the ground in great numbers; a good way to gather beechnuts, but one that would hardly avail to gather the cochineal.
The males are very much fewer than the females, only one of the former being found to one or two hundred of the latter. At the proper season for collecting them, the females attach themselves to the leaves and grow so fat and corpulent, that their snouts - of which they have at first an ample allowance - their antennae, and legs almost totally disappear, and the insects look more like excrescences than anything having life.
They are now gathered by means of a blunt knife, a quill, or its equivalent, and killed, etiher by inclusing them in an bag and immersing them in boiling water, or by heating them in a stove. If boilin water is used they are subsequently dried in the sun. The wild variety yield, it is said, six crops, and the cultivated variety three crops annually. The insects after drying, are sitted, and the dust forms an inferior article of commerce called granillo.
The coloring matter which renders this insect valuable is very soluble in water, in cold alcohol, and sitll more in boilin alcohol, but insoluble in ether. It has been called by the chemists cochinilin, and more recently carmonic acid, on accoun of its acid properties. According to De la Rue, it consists of carbon, hydrogen, and oxygen, in the proportions expressed by the formula C28H14O16 or 169 parts of carbon, 14 parts of hydrogen, and 128 parts of oxygen by weight.
It may be obtained by digesting the insects in ether to remove the fat, disolving the residue in water and adding acetate of lead, when a lead carmine lake will be precipitated. This is washed, dissolved, and decomposed by hydrosulphuric acid, which precipitates the lead as a sulphide leaving the carminic acid in solution, which is separated by evaporation. Carminic acid is a purple-brown friable mass, soluble in all proportions in alcohol and water, and unchangeable by the action of strong sulphuric or hydrochloric acid. It forms purple lakes with salts of copper zinc and silver; and with tin, a bright crimson. Very fine lakes are also prepared by its combination with fine gelatinous alumina.
When pure it is harmless but it is often shamefully adulterated with lead salts and vermillion, which are poisonous.
Cochineal is used larggely in dying, in fine painting, in coloring confections, and in the perdumer's art, where it forms the basis of a number of the finest preparations called rouges. The following is one of the best recipes for the manufacture of this sort of pigment, and it can be easily prepared by any one. It is perfectly harmless to the skin.
Recipe. - Extract the coloring matter from cochineal (obtainable at any good druggist shop) by digestion with alcohol; filter the tincture, add a little solution of gum-arabic, and boil down to a thick liquor. The boiling should be done in an earthern vessel set in a pan of boiling water. When the liquid has become sufficiently thick it may be spread evenly over the inside of a saucer. Thus ladies may have it in their power to make themselves blush to any desirable extent, without the aid of the perfumer, and without fear of deleterous effects upon then skin from poisonous adulterations.
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