BLUES (1) Methyl Blue (30 lb. yarn).—Dissolve -I lb. Glauber salts, 2 lb. alum, in a sufficient quantity of water. Dissolve oz. methyl blue (of Meister, Lucius, & Bruning), and add it to the dye-heck. Enter yarn at 43° (110 F.), turning rapidly, and dye to shade, raising tho temperature to 49° (120° F.).
(2) Light Blue (50 lb. bleached yarn).—Dissolve 3 lb. alum, 3 oz. tai Laic acid, and oz." water blue 6 B " (Berlin Aktien Gesellschaft fiir Aniliu-Farben). Enter yarns at 43° (110° F ), turn rapidly, and raise tho temperature to 54° (130 F.), turning to shade. After tho colour has become level, another oz. of the colour, previously dissolved, should be added to the beck.
(3) Corn Flower Blue (Pittacal).—Prepare the cotton in a cold solution of tannin ; wring, and enter into a solution of tartar-emetic. Wring, and enter into a solution of acetate of pittacal,—dis solved in acetic, acid, diluted with a eufficient quantity of water, and then almost neutralized with ammonia.
(4) Nary Blue (11 lh.).—Boil 2 lb. 3 oz. logwood, and dissolve in the clear hot liquid 26 oz. curd soap. Steep clear yarn in this liquor for 2 hours at 75° (167° F.). Lift ; add to the beck 26 oz. copperas ; re-enter the yarns, and work till the colour is even. Wash in cold water, and work in a fresh beck, with 17} oz. curd soap, at 62° (144° F.), for 1 hour. Then make up a boiling beck with 2* oz. of an aniline blue, soluble in spirit, and 2 lb. 3 oz. red liquor at 13° Tw, Work the yarn in this at a boil till the desired shade is obtained, and finally rinse.
(5) Aniline Blue (11 lh.).—Boil 2 lb. 3 oz. sumach, or 61 oz. tannin, in water ; filter ; dissolve 17} oz. curd-soap in the clear solution, and enter the cotton over night into the hot liquor. Wring out, and make up a heck with acetate of alumina at 3° Tw., to which a clear solution of aniline blue is added according to the shade. Enter the cotton, and dye, raising the temperature to a boil for some time.
(6) Methylene Blue.—This colour dyes cotton without a mordant, producing rich blues with a greenish reflection, fast against soap and light. It dissolves readily in water.
(7) Indigo or Vat Blues.—Indigo, being insoluble, cannot be applied to textile fibres by the ordi nary dyeing processes. It requires to be reduced, to so-called "white indigo," when it becomes soluble, and is in that state deposited on the tissues of yarns, where it rapidly resumes its ordinary blue insoluble condition, and remains permanently fixed in the fibre.
In the case of ootton, the indigo vat is generally " set " in the following method. To about 2000 gal. water, are added 60 lb. indigo, ground to an impalpable powder, 180 lb. slaked lime, and 120 lb. copperas. The lime and the copperas are added from time to time. The lime is put in first, and the vat is well stirred up before adding the copperas. There must be always sufficient lime present to dissolve the white indigo as it is formed. But if too muoh lime be present, an insoluble compound is formed, which renders the indigo useless for dyeing.
The yarns or pieces are simply steeped in, or rinsed through, the clear liquid of the vat, and then exposed to the air, when the greenish colour which they take at first is soon converted into a blue. The dipping and airing are repeated till the shade is obtained. The goods are then taken through very weak sulphuric acid, thoroughly well washed, and dried.
The vat for dyeing cotton, or any other vegetable fibre, is always worked in the cold.
An improvement in vat dyeing was invented and patented some years ago, by Schutzenberger and De Lalande. A solution of the bisulphite of soda, at 52°-63° Tw., is placed in a covered vessel, containing zinc-clippings, borings, &c., piled up, so as to fill the tank, without occupying more than a fourth part of its total contents. After 1 hour's contact, the liquid is drawn off into a cistern, con taining milk of lime, which decomposes the zinc salts. The clear liquid is then strained off; soda or lime, sufficient to dissolve the indigo, is then added, and it is mixed with the indigo, which must be in perfectly fine powder. At once is produced a yellow solution, containing no soluble impuri ties, except the earthy matters which were present in the indigo itself. Access of air is avoided as much as possible during this process. In this manner, 2 lb. 3 oz. indigo can be dissolved in 7f-26 pints liquid. The vat is then filled with cold water, if for cotton, and a suitable amount of the indigo solution is added. An excess of the " hydrosulphite " is always present, whence the blue scum, which, in the common process, is formed on the surface by the action of the air on the reduced indigo solution, is almost wholly avoided, the blue indigo being reduced as quickly as formed. The dye-liquor thus resists atmospheric action far better than the ordinary copperas vat ; and it is free from the inconvenience of always holding in suspension more or less peroxide of iron, carbonate of lime, &c., which must be allowed to settle before the vat can be used with advantage. By adding to the vat from time to time a little concentrated indigo solution, the strength can be maintained at any required point, and thus any given shade may be communicated by the smallest number of dips ; the colours thus obtained are also brighter than those of the old process.
(8) Prussian Blue (10 lb.).—Take 1 pint muriate of tin, 4 qts. of nitrate of iron (so-called blue-iron), and 30 gal. of water. Run the cloths or yarns 4 times through, and wash off.
Dissolve 1f lb. yellow prussiate of potash (potassium ferrocyanide) in 30 gal. water, and add to it f pint oil of vitriol (full strength sulphuric aoid). Run the piece, or turn the yarns, 4 times, and then raise the colour in a beck of 30 gal. of water, I pint nitrate of iron, ands pint oil of vitriol. Wash off, and dry.
Prussian blues are now almost entirely superseded by the coal-tar blues.