ANILINE BLUES.

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high and the latter at a low temperature. Sulphuric acid, or in case of silktartaric acid, may be added to the dye-bath with advantage.

The opal blues are still less soluble. They should be ground to a very finepowder, and well rubbed together with sulphuric acid sufficient to moisten thecolour. The acid employed should be perfectly free from lead and from nitro-gen compounds. Alcohol is then added, sufficient to dissolve the whole. Themixture is raised to the boiling-point, and maintained at that temperature tillall is dissolved. The liquid is then very carefully filtered.

For cotton these blues have no affinity, and the attempts to fix them uponthat fibre in dyeing have not been very successful. In printing they may befixed by means of albumen or ladtarine, as described under Magenta. Thefollowing modification of Perkin’s process may be successfully used for blues,as well as for all aniline colours whose colouring principle is a base. Arseniousacid is dissolved in pure glycerine to saturation. To each gallon of thethickened aniline colour from one-eighth to one-fourth part of this solution isadded, together with an equivalent amount of acetate of alumina. The colouris then printed upon calico, bleached as for madder, and steamed at a pressure ofabout i lb. per square inch for some three-quarters of an hour. The glycerineis thus dissipated, and an insoluble compound of arsenite of alumina and ofthe coloured base is produced in the fibre of the cloth. After steaming, thecolours are not, as a rule, very bright, but may be rendered so by treatmentwith boiling soap-lye for half an hour. It seems probable that in this soapinga portion of the arsenite of alumina is decomposed, with the produdtion of acorresponding amount of stearate or oleate—the stearates and oleates of theaniline bases, and their double salts; but no diredt use seems as yet to havebeen made of them in dyeing cotton, if we may except the following process,which finds a limited application in skein-dyeing. The cotton skeins are firstdipped or worked in a solution of alum, and after being well squeezed out ordried they are worked in a bath of soap-lyes. They then take up anilinecolours with great facility, but the combination between the fibre and colouringmatter is not very stable so far as washing in soap is concerned, though thecolours resist light fairly.

In dyeing piece-goods made of a mixture of animal and vegetable fibre,—such as delaines, coburgs, &c.,—the worsted is first made to take an anilineblue in the ordinary manner. The cotton-warp is then dyed a very brightPrussian blue, with “ blue-iron ” (see chapter on Mordants) and ferrocyanideof potassium. Several mordants have been tried for fixing the aniline blueupon the cotton. Amongst others, the nitrate of sesquioxide of chromeenables the aniline blues to lay a firm hold upon the cotton, but unfortunatelyat the same time it injures the brightness and purity of the colour alreadydeposited upon the wool or worsted, turning it do a dull purple or slate.

The Nicholson and Guernsey blues are dyed as follows :—For woollenpiece-goods the bath is made alkaline with soda, borax, or silicate of potash.The colour is then added very gradually. The goods are entered at about120° F., and worked up slowly to just below the boiling-point, at which thebath is kept for twenty minutes or half an hour, according to the shaderequired. The cloth is then taken out, washed well in cold water, and workedin a bath slightly acidulated with sulphuric acid, in order to develope thecolour. The pieces are finally washed in cold water. In order to ascertain