Weld is the dried top and seeds of Reseda luteola, cultivated generally throughout Europe. The coloring principle is called luteolin. It is regarded as the best and fastest of the natural yellow dyes for silk, and is used chiefly on alumi num and tin mordants, yielding greenish yellow and bright yellow. With other mordants are secured shades of olive-yellow.
Young Fustic, the ground wood or extract of the Venetian Sumac (Rhus cotinus), a tree growing in southern and eastern Europe, the Levant, Jamaica, etc. The coloring principle is fisetin. Young fustic, which is not “fustic)) at all, imparts shades of yellow which are so fugi tive to light and the milling processes as to be seldom used.
Mineral dyes, though formerly in extensive use, have been largely displaced by the coal tar dyes. However, they are generally very fast to light and the laundry, and being cheap are still employed to a considerable degree. Their dyeing qualities are due to the deposit of insoluble pigments in the fibres of the fabric dyed.
The few mineral colors now in use are the following: Bistre, see Manganese Brown.
Chrome Yellow, chemically chromate of lead, is used on cotton only. The fabric is first impregnated with nitrate or acetate of lead, which is then changed to the oxide by ammonia, or to the sulphate by sodium sulphide. It is then passed through a weak solution of potas sium bi-chromate. All the chrome colors are pOisons, and they are continued in use chiefly because they weight the fabric heavily.
Chrome 'Orange is produced by first dyeing the fabric with chrome yellow, and then passing it through boiling dilute limewater.
Chrome Green is usually produced by first dyeing the goods with a light shade of indigo blue, and then with chrome yellow.
Khaki is produced on cotton by passing the cloth, after scouring, through a mixture of ferrous and chromic acetates and drying; then aging and passing through a boiling mixture of caustic soda one part and carbonate of soda three parts.
Manganese Brown, or Bistre, is produced on cotton by impregnating the fabric with a solution of manganese chloride, and then passing it through a hot solution of caustic soda —.which precipitates the manganese hydroxide in the fibre. On exposure to the air this oxidizes to a brownish hue, and the color is improved and finished by immersion in a weak solution of chloride of lime.
or Nankin Yellow, is produced by precipitating a ferric salt with an alkali, or alkaline carbonate. It is used principally on cotton.
Prussian Blue is produced on cotton by first mordanting the fibre with ferric oxide, and then immersing it in yellow prussiate of potassium.
It is also used in weighting silks which are afterward to be dyed black.
The coal-tar colors which constitute the class of artificial organic dyes are practically in numerable. Several thousand of these dyes have been prepared and hundreds of them have been named. New ones are continually being discovered in new combinations, and many which formerly were highly esteemed have been super seded by better ones.
From the dyer's point of view, these multi tudinous dyes have been thus classified: I. Direct Cotton Colors, or Salt Colors — which, in a neutral or weakly alkaline bath con taining common salt or Glaubersalt, dye cotton in full shades without mordants.
II. Sulphide Colors, or Sulphur which, dissolved with the aid of sodium sul phide, dye cotton in full shades from a sulphide bath without mordants.
III. Basic Colors— those having the quali ties of bases, dyeing animal fibres without mor dants, and vegetable fibres with tannin mordants.
IV. Eosins and Rhodaznines excep tional brilliancy; the first for silks, the second for silks, wools and tannin-mordanted cotton and cotton-mixed goods.
V. Acid Colors — salts of color acids, dye ing animal fibres without mordants.
VI. Mordant Colors — which require me tallic mordants to fix their colors.
VII. Acid Chrome requiring an acid bath; they dye on wool with chrome mor dants.
VIII. Miscellaneous Colors — including aniViii. Miscellaneous Colors — including ani- line black; indigo and other vat dyes; and the insoluble azo-colors, known as 4 ice-colors." Space does not permit specification of even the coal-tar colors in commonest use. For a condensed review of upwards of 900 of the more prominent of these dyes the 'student is referred to Arthur C. Green's Colour ing Matters.) See also COAL-TAR COLORS.
The United States census of manufactures for 1914 reported 112 establish ments of factory grade manufacturing dyestuffs and extracts in the United States in that year. They employed 3,551 persons, of whom 2,839 were wage earners, receiving annually a total of $1,613,000 in wages. The capital invested aggre gated $21,283,974, and the year's output was valued at $20,620,336; of this, $7,382,341 was the value added by manufacture to the $13,237, 995 worth of materials used. In addition, there were 22 establishments which reported dyestuffs and extracts as subsidiary products. Their value for the year specified was $764,353. Consult Cain, J. C., and Thorpe, J. F., 'The Synthetic Dyestuffs> (London 1913) ; Fay, I. W., 'Chem istry of the Coal-Tar Dyes) (New York 1911) ; Knecht, E., Rawson, C., and Loewenthal, IL, (A Manual of (London 1910).