YELLOW VEGETABLE COLOURS.

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blue precipitate; nitrate of lead, violet-red precipitate; acetate of copper,chestnut-brown precipitate.

According to Dr. Glenard the formula of oenolin is Ci 0 H io O 5 . Youngwines contain, moreover, according to Dr. Filhol, a peculiar blue colouringmatter, soluble in acetic and butyric ethers, yielding bright, beautiful, violet-blue solutions, which, by the addition of some ammonia, become first greenand next brown. The chemist just named considers that this substance isidentical with cyanin as met with in many flowers.

The colouring matter of wine is not industrially employed as a dye, but itsproperties are of importance, since they may assist in detecting frauds and beuseful in medico-forensic researches. Genuine wines are often artificiallycoloured, but in the wine-growing countries this is done by the addition to thefermenting must of a peculiar kind of grapes, of a very deep blackish-bluecolour, purposely cultivated—as, for instance, at Lespane and many otherlocalities—for its colouring qualities.

Among the vegetable colours we notice with a word the following :—

The red cabbage colour, probably cyanin (“ Dingler’s PolytechnischesJournal,” vol. xvi., p. 268): this material becomes green by alkalies,and was formerly in use as a test for them in chemical laboratories.

The red matter of the red poppy flower (“ Dingler’s Pol. Journ., vol. xxii.,p. 271).

The so-called dragon’s-blood, a red-coloured resin, the produce of a kindof palm tree, a native of Sumatra and Borneo (“Journal de Pharmacie,”vol. xvii., p. 225 ; “ Annalen der Chimie und Pharmacie,” vol. xliv.,p. 328 ; “ Comptes Rendus,” vol. xvii., p. 503 ; vol. xix., p. 505).

The Lithospermum rose-red (“ Repertoire de Chimie Appliquee,” vol. i.,p. 209 ; “ Archiv. der Pharmacie,” vol. cxlvi., p. 278).

The peculiar red of the red cinchona barks.

The bark of the Lithospermum arvense yields, when treated with alcohol, adeep red-coloured resinous substance ; the alcoholic tindture of deep red colourturns blue upon the addition of alkalies. This resin is soluble in strong sul-phuric acid, and exhibits great analogy with anchusin, but is distinguishedfrom it by the colour of its ethereal solution, which is blue, and not red, as isthat of anchusin.

Yellow Vegetable Colours.

Of the colours met with in the vegetable world none is so abundant andwidely distributed as the yellow, which occurs in almost all plants to a greateror less extent, while the researches of Dr. Thudicum on lutein, of which thefollowing is a brief abstract, prove the identity of some of the yellowcolouring matters of the vegetable and animal kingdom :—

By lutein Dr. Thudicum understands a yellow crystalline substance occur-ring in various parts of animals and plants, as, for instance, the corpora luteaof the ovaries, serum of blood, yolks of eggs, in seeds, as maize (Indian corn),in annatto, in carrots, and the stamens and petals of a great many flowers.Lutein is easily soluble in alcohol, ether, and chloroform, insoluble in water;these solutions are yellow, but that in chloroform, when concentrated, has anorange-red colour. The spedtrum of its solutions is distinguished by greatbrilliancy of the red, yellow, and green part, and by three absorption bands,which are situated in the blue, indigo, and violet part of the spebtrum. The