. Cyclopedia of farm crops. Farm produce; Agriculture. DYES AND DYEING DYES AND DYEING 271 The goods are first treated with a solution of one of the chemicals, and then on working in another solution the pigment is produced. In calico-print- ing, any pigment can be fastened mechanically as in ordinary printing, except that gum arable, dex-. Saifron {Cntctis satitnts). Source of a yellow dye. Fig. 376. trin, starch, albumen, and the like, are employed instead of varnishes. Definitions. Lakes are insoluble compounds of alumina and coloring matters. If these are formed by them- selves, a color-la
. Cyclopedia of farm crops. Farm produce; Agriculture. DYES AND DYEING DYES AND DYEING 271 The goods are first treated with a solution of one of the chemicals, and then on working in another solution the pigment is produced. In calico-print- ing, any pigment can be fastened mechanically as in ordinary printing, except that gum arable, dex-. Saifron {Cntctis satitnts). Source of a yellow dye. Fig. 376. trin, starch, albumen, and the like, are employed instead of varnishes. Definitions. Lakes are insoluble compounds of alumina and coloring matters. If these are formed by them- selves, a color-lake or pigment is produced ; but if a fabric is first impregnated with alum or other metallic salts for which the fiber has an affinity, on subsequent treatment in the coloring solution the color-lake is produced in and on the fiber, which is then said to be dyed. Several other metallic oxids also possess similar properties, often giving differ- ent colored precipitates with the same dyestuffs. These metallic compounds are called "mordants" (from the French mordre, to bite). Tannic acid forms insoluble compounds with an entire series of coloring matters and is similarly Although dyeing has been practiced from time immemorial, and by all nations of the globe, no satisfactory theory has been advanced to explain the process. Mechanical attraction, chemical affin- ity and "solid solution " are given as explanations, all having experimental evidence in support. In wool dyeing, the chemical affinity theory best elucidates the process. Classification of dyestuffs. The dyestuffs may be classified either according to their chemical composition, in accordance with the fibers for which they are most suitable, or with the methods used in their application. The first classification is of importance to the chemist, while the last is best for practical purposes, and is shown in the following grouping : (a) Direct cotton colors. These dye cotton in full shades without
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