TURNBULL'S BLUE 1047 



being washed, are passed through a warm solution of tannin, prepared by extracting 

 galls or sumac with boiling water and straining, after which they are impregnated 

 with a solution of alum, to which sometimes a little chalk or carbonate of potash is 

 added, or with a solution of acetate of alumina, prepared by double decomposition 

 from alum and acetate of lead. Sometimes the alum is dissolved in the decoction of 

 galls, and thus the two operations are combined into one. The goods, after being 

 dried in the stove, passed through hot water containing chalk, and rinsed, are now 

 ready to be dyed. It has been asserted that the galling is not an essential part of 

 the process, that it merely serves to fix the alumina of the mordant, and may be 

 dispensed with when acetate of alumina is used instead of alum. It is certainly 

 difficult to conceive how it can permanently affect the appearance of the colour, since 

 the tannin of the galls is undoubtedly removed from the fibre during the subsequent 

 stages of the process. 



The dyeing is performed in the usual manner. (See MADDER and CALICO-PRINT- 

 ING.) The materials employed are madder, chalk, sumac, and blood, in various rela- 

 tive proportions. The heat of the dye-bath is gradually raised to the boiling point, 

 and the boiling is continued for some time. The part played by the chalk in dyeing 

 with madder has been explained elsewhere. (See MADDEB.) It was formerly supposed 

 that the red colouring-matter of the blood contributed in producing the desired effect 

 in Turkey-red dyeing ; but to the modern chemist this supposition does not appear 

 probable. Nevertheless, it is certain that the addition of blood is of some benefit, 

 though it is uncertain in what the precise effect consists. Glue is occasionally em- 

 ployed in the place of blood. Sometimes a second mordanting with galls and alum, 

 and a second dyeing, is allowed to succeed the first mordanting and dyeing. 



After being dyed the goods appear of a dull brownish-red colour, and they must 

 therefore be subjected to the brightening process, in order to make them assume the 

 bright red tint required. For this purpose they are first treated with a boiling solu- 

 tion of soap and carbonate of potash or carbonate of soda, and then with a mixture of 

 soap and muriate-of-tin crystals. This operation is usually performed in a close vessel 

 under pressure. The alkalis remove the brown colouring-matters and the excess of 

 fat-acid contained in the colour, and the tin salt probably acts by extracting a portion 

 of the alumina of the mordant, and substituting in its place a quantity of oxide of tin, 

 which has the effect of giving the colour a more fiery tint. The last finish is given 

 to the colour by treating the goods with bran or with chloride of soda. 



The chief objects which the Turkey-red dyer seeks to attain are, 1st, to obtain the 

 desired effect with the least possible expenditure of time and material ; .2nd, to pro- 

 duce a perfect uniformity of tint in the same series of dyeings ; and 3rd, to impart to his 

 goods a colour which, though perfectly durable, shall be fixed as much as possible on 

 the surface of the fabric. The last point is one of importance in the case of calicoes 

 dyed of this colour, since this kind of goods is much employed for the production of a 

 peculiar style of prints, in which portions of the colour are discharged, in order either 

 to remain white or to be covered with other colours. (See CALICO-PRINTING.) And 

 if the red dye is too firmly fixed, or too deeply seated, it becomes more difficult to 

 discharge it. In this respect the art has in modern times attained to such a degree of 

 perfection, that the interior of each thread of Turkey-red cotton will be found on 

 examination to be perfectly white. This is particularly the case with the Turkey- 

 reds from the establishment of Mr. Steiner, Accrington, Lancashire, whose productions 

 in this branch of the art of dyeing are also unrivalled for the brilliancy and purity of 

 their colour. E. 8. 



TURMERIC (Curcuma, Terra inertia, Souchet or Safran des Indes, FT. ; Gelb- 

 wurzcl, Ger.) is the rhizome of the Curcuma longa and C. rotunda, a plant which grows 

 in the East Indies, where it is much employed in dyeing yellow, as also as a condiment 

 in curry sauce or powder. The root is knotty, tubercular, oblong, and wrinkled ; 

 pale-yellow without, and brown-yellow within ; of a peculiar smell, a taste bitterish 

 and somewhat spicy. It contains a peculiar yellow principle, called Curcumim', a 

 brown colouring-matter, a volatile oil, starch, &c. The yellow tint of turmeric is 

 changed to brown-red by alkalis, alkaline earths, subacetate of lead, and several 

 metallic oxides ; for which reason, paper stained with it is employed as a chemical 

 test. 



Turmeric is employed by the wool-dyers for compound colours which require an 

 admixture of yellow, as for cheap browns and olives. As a yellow dye it is employed 

 only upon silk. It is a very fugitive colour. A yellow-lake may be made by boiling 

 turmeric-powder with a solution of alum, and pouring the filtered decoction iipon 

 pounded chalk. 



TURNBITXiXi'S BXiUE. Ferricyanide of iron, obtained by precipitating a solu- 

 tion of a salt of protoxide of iron with ferriryanide of potassium. See BLUE PIG- 

 MENTS and PRUSSIAN BLUE. 



