ABSTRACT
The vegetation which clothes so large a part of the earth’s surface, though differing so much in form, height, structure, and general character from the tropics to the limits of temperate zones, agrees in one character, namely, the colour of the foliage when young and active. Treatment of chlorophyll with alkaline reagents fails to disturb the magnesium, but it is extracted and removed by the action of acid liquids. Many vegetable colouring matters were extensively used as dyes before the discovery of the coal-tar colours, and a few still retain their position. It is only necessary to remind the reader that, notwithstanding the advent of the very numerous synthetic dyes, natural indigo, logwood, safflower, and madder colours are still used to some extent in the dye house, and that the colouring matters of the damask rose, the red poppy, turmeric root, litmus, and red cabbage are employed in other ways.
