ALIZARIN.

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layer. The whole should then be kept for some time in a well-closed vessel,and left standing undisturbed. The ether slowly mixes with the rest of thefluid, and the alizarate of soda separates in the shape of needles. The alka-line earths and metallic oxides yield, with alizarin, compounds insoluble inwater, and which are violet, red, or black. Some of these are technicallyknown as lake-colours. Those of alumina are red or rose-coloured, whilstthose of peroxide of iron are violet or black. The true composition of thesesalts is but imperfectly known. The carbonates, phosphates, pyrophosphates,borates, silicates, oleates, and generally all the salts capable of turning redlitmus-paper blue, dissolve alizarin, especially with the aid of heat, yieldingreddish-violet coloured solutions. Liquid ammonia ads upon alizarin in avery peculiar manner, which reminds us of the behaviour of carminic acidunder similar circumstances. Ammonia first dissolves alizarin, yielding acharacteristic solution of a violet-blue colour. From this solution acids throwdown the alizarin unchanged, in the shape of yellow flocks. But if the solu-tion is kept in a closed vessel for at least twelve hours, at a temperature oftoo 0 C., or preserved for several weeks at common temperatures, acids nolonger precipitate it as before, but cause the appearance of a deep violet floc-culent mass, containing the elements of alizarin and ammonia combined in sostable a manner that even strong acids do not cause its decomposition. Thissubstance—called by its discoverer, Schutzenberger, alizaramide or alizareine—is formed without contad of air, and without the adion of oxygen. In a wetstate it is of a reddish-violet colour, but when dry quite black. It is perceptiblysoluble in water and in alcohol, even when dilute, yielding a beautiful violet-red solution. It is also soluble in ether. On evaporation of the alcoholicsolution it is obtained in crystals. If heated on platinum foil it burns withoutsublimation. When boiled with caustic alkali, alizarinamide gives off ammonia,but no ammonia is evolved when it is rubbed up with dry caustic lime in amortar. Cloth, previously mordanted and then dyed with this substance,assumes colours somewhat similar to those yielded by madder, though lessrich, and accompanied by a pale violet hue. Wool is dyed by this colour of adirty lilac, without the aid of any mordant.

When alizarate of soda, in crystals, is heated in a sealed tube to 120° C.,along with iodide of ethyl, an ethylic derivative is obtained of a bright yellow,insoluble in water and soluble in alcohol.

Chloride of benzol ads upon alizarin at igo® C. Hydrochloric acid is givenoff, and a compound formed which is insoluble in water, soluble in alcohol,but insoluble in ammonia at ordinary temperatures. When boiled with alka-lies it is saponified, the result being the formation of an alkaline benzoate andalizarate.

Alizarin is readily aded upon by oxidising agents. Nitric acid and per-chloride of iron convert it into phthalic and oxalic acids.

The adion of reducing agents upon alizarin has not been fully investigated.If an alkaline solution of alizarin is heated along with aldehyd the violetliquid turns orange, and on the addition of an acid a yellow flocculent preci-pitate falls. Nascent hydrogen discolours the solutions of alizarin.

According to the recent researches of Graebe and Liebermann, alizarin,treated with powdered zinc and hydrochloric acid, yields a hydrocarbon—anthracen. Starting from this discovery the authors have devised a method