DYEING AND CALICO PRINTING.

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addition to the ink of some corrosive sublimate, or, if this poison is dreaded,there may be added a few drops of essential oil of cloves or a trace of carbolicacid. The viscosity of ink is frequently due to the use of inferior materials inits preparation, and to the negledt of filtering it through good filtering-paper,an operation which is always very tedious.

Gallein.

A dye, or rather class of dyes, may here be noticed which stand in a closerelation to the astringents, and are prepared from pyrogallic acid. The firststep is the preparation of gallein. For this end, the inventor, Baeyer, heats amixture of I part of anhydrous phthalic acid and 2 parts of pyrogallic acid to200° C., and keeps the mass at that temperature for some hours. When cold,the residue is treated with hot alcohol, the solution is filtered and diluted withwater, which throws down a precipitate of the new body, gallein. It is of areddish-brown colour, but when in large lumps it exhibits a greenish-yellowmetallic refledtion. It is insoluble in cold, and sparingly soluble in boiling,water, forming a red solution. In alcohol, it dissolves readily with a deep redcolour. It is also soluble in caustic potash lye with a blue, and in ammoniawith a violet, colour.

Gallein is in many respedts analogous to haematin. Trimesic, pyromelliticand prehnitic acids, and the oil of bitter almonds also yield gallein on fusionwith pyrogallic acid.

The composition of gallein is found to be CisH^Oy. If treated with zincand dilute sulphuric acid, it is converted into gallin,—a solid, colourless,crystalline body, soluble in ether, and still more readily in an aqueous solutionof pyrogallic acid. When dried in a vacuum, its composition was found tocorrespond with the formula C^H^Os. It is sparingly soluble in cold, butreadily in boiling water, and still more readily in alcohol. Both in the solidstate and in solution it becomes very readily pink-coloured. It dyes tissuesin the same manner as gallein.

Gallein, if treated with concentrated sulphuric acid at 200° C., yieldsccerulein, CjsHjoOs. This body is almost insoluble in water, alcohol, andether. In acetic acid it dissolves more readily, forming a dirty greensolution. It is easily soluble in hot aniline, yielding a solution of a splendiddeep blue colour, which, if acidified with acetic acid, dyes wool indigo-blue.Ccerulein dissolves in alkaline liquids with a beautiful green colour. Thesolution dyes tissues previously mordanted with alumina a fine green. If aniron mordant be used, the resulting shades are brown. Both these dyes arefast, and resist soaping. There appears to be a resemblance between cceruleinand Lo-kao (Chinese green).

Reducing agents convert ccerulein into coerulin, which dissolves in etherwith a yellow colour. If anhydrous phthalic acid is allowed to adt uponresorcin, fluorescein is formed,—a yellowish-red body soluble in alcohol. Itis a substantive colour, and dyes silk and wool yellow without the aid of anymordant.

The following substances, though possessing tindlorial powers, and capableof being applied in dyeing and printing, are, from a variety of reasons, not inadtual use:—

Alder Bark contains a colouring principle, along with tannin. With