DYES AND DYEING. Figs. Dyestuff materials are derived from the animal and vegetable kingdoms, and, in the last fifty years, those made synthetically from products obtained from coal-tar. In 1856, W. H. Perkin, an English chemist, discovered the production of a violet dye when experimenting with aniline, a body found in coal-tar ; soon afterwards, other dyes were made from the same products and they became known as aniline colors. Unfortunately, these colors were inferior to the natural coloring matters, which they surpassed in brilliancy, so that, although very many artificial colors have been made that equal or surpass those derived from natural products (in some instances the identical natural product being made synthetically), "aniline colors" even today are regarded in the popular mind with more or less suspicion. Over twenty-five thousand patents have been taken out covering these dyes or processes relating thereto, and more than two thousand arti ficial dyestuffs have found more or less commercial value. The natural coloring matters are rapidly becoming of historic interest only and their cul ture is being abandoned. A few are now secured from native trees of the forest. Twenty-five years ago madder began to be replaced by alizarine, the coloring principle found in it, which is now manufactured in enormous quantities ; and within the last six years, the artificial production of indigo has been compelling the producers of the natural product to improve their methods or succumb. Indeed, it is only the cheap labor of India that renders any competition possible.
Dyestuffs are used for coloring all sorts of materials. Addition of coloring matter to a food product to disguise its appearance or character partakes of the nature of fraud. Harmless color ing materials may be used in confectionery and the like, where it is evident that no deceit is intended.
Coloring materials vary so much in properties that it is not possible in this place to give the de tails of their extraction. Coloring matters that
exist as such are extracted with the proper solvent : water-alcohol and ether are the chief solvents. Many of the natural coloring matters, such as that of logwood, are not found in plants in the free state, but in combination with a glucose-like body, and are called glucosids, and only after a kind of fermentation or oxidation is the coloring principle in condition to be extracted. In common with many plants possessing medicinal properties, the special ferment also exists in the plant, so that fermen tation proceeds when the proper conditions are met.
List of natural animal and vegetable colors.
The following very complete list of natural col ors of vegetable and animal origin, compiled by Wilton G. Berry and published in Circular No. 25, of the Bureau of Chemistry, Department of Agriculture, rescues from oblivion many coloring matters and fairly indicates their importance and use. The source of the color is given in Italics : Alder bark : Alma glutinosa. Yellow.
Alkanet : Baphorhiza tinctoria (Alkanna tinctoria, Anchusa tinctoria). Used in coloring oils, medicines, po mades, wine, etc. Red to crimson. Alkanna green has also been prepared from the root.
Aloes : Cape aloe (Aloe spicata), A. arborescens, A. lucida, A. Succotrina, A. vera. Yellow.
Al root or Aich root, soorangee, suranjee (India) : Morinda citrifolia, M. tinctoria. Alumina lake, yellow.
Annatto, or anotto, orlean, roucou, orenetto, attalo, terra orellana, achiote : Bixa Orellana. Used for color ing oils, butter, etc. (Fig. 372.) Archil, or orchil, orseille, oricello, ()raffia Rocella Montagnei (new), R. fuciformis (old), R. tinctoria. Also prepared from any lichens containing orcin or its deriv atives, i. e., Variolaria, Leranora, Evernia, Cladonia, Ramalina, Usnea. Appears in liquid, paste, and powder forms, the latter being a sulfonated derivative. Dyes unmordanted wool in neutral, alkaline and acid solutions, giving 'a bright bluish red. The color is not fast to light.