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DYEING AND CALICO PRINTING.

and 2 lbs. of nitrate of iron for about five turns, and are wrung out. Theyarn is next taken through a strained cold bath of 4 lbs. of lime for fiveturns, and the colour is submitted to oxidation in the air. When even, theyarn is again dipped in the iron bath and again in the lime, and oxidiseduntil the desired shade is obtained. The colour is fast.

Gold leaf, pure or alloyed, or imitation, is applied to woven tissue by meansof albumen or a fatty and resinous mordant.

GREEN MINERAL PIGMENTS.

Mineral greens may be divided into two groups. To the first belong thosemineral compounds possessing a green colour and well-defined chemicalconstitution, as chrome-green or hydrated oxide of chromium ; Scheele’s greenor arsenite of copper; Schweinfiirt green or aceto-arsenite of copper; and theemerald greens. The second group includes all those various shades of greenwhich are composed of mixtures of blue and yellow pigments, and constitutesimply mechanical mixtures.

The larger proportion of green pigments belonging to the first group arepreparations derived from chromium and copper, to which may be addedRinmann’s green, a compound of cobalt and zinc, Rosenstiehl green ormanganate of baryta, green ultramarine, and some green prussiates. AsGuignet’s green, a chrome-green, is extensively used, it may be interesting toknow how it is produced. Three parts of boracic acid are intimately mixedwith one part of bichromate of potash and a sufficient quantity of water toform a thick paste. The paste is introduced into a furnace and heated to adull red heat, when a borate of potash and a borate of oxide of chromium areproduced. The mass is allowed to cool, and is then thrown into cold water;the borate of potash is dissolved, and the borate of chromium is decomposed;the hydrate of the oxide of the metal C2O3+3HO subsiding as a magnificentgreen powder, which only requires to be well washed and drained to be readyfor use. This green and that prepared from phosphate of ammonia andbichromate of potash possess the property of maintaining their colour byartificial light.

Chrome-green, like other pigment colours, is fixed either with ladtarine, orwith albumen thickened with gum or starch. In either case the cloth issubsequently steamed.

Among the preparations of copper that possess a green colour only afew are employed in dyeing and printing. The principal are—Arsenite ofcopper, termed Scheele’s green, and designated by as various names astheir places of manufacture, is a compound the constitution of which isexpressed by the formula As204Cu" I]: . This pigment may readily be fixed totissues by first passing them through a solution of a salt of copper, thenthrough a soda bath to fix the blue hydrate of oxide of copper, and finallythrough a solution of arsenious acid. A more expeditious method consists inpassing the fabric through a bath of arsenite of soda, and then through asolution of a salt of copper, generally the sulphate. The accompanyingspecimen of printed cloth, from the firm of Messrs. Wood and Wright,coloured with Wilner green, by an arsenical process, illustrates the applicationof this class of pigment colours. The process is as follows:—4 lbs. of sul-phate of copper are dissolved in 1 gallon of hot water, and the solution is