Vegetable coloring matters.

The Galaxy 4, 1871

DR. H. C. Sorby has lately been studying the vegetable coloring matters by means of spectrum analysis, directing attention chiefly to the various tints displayed by autumnal foliage. He finds from careful examination that these are readily divisible into groups or genera, which again break up into smaller groups or species. Beginning with what Dr. Sorby calls the chlorophyl group, it appears that what has hitherto been regarded as a single substance, is really made up of several sorts of coloring matter, and that the green coloring matter contained in most leaves really consists of a mixture of two or more of these. All the chlorophyl group have the following peculiarities in common: They are insoluble in water, but soluble in alcohol or bisulphide of carbon; the spectra have all a vet), well marked absorption band in the red, but the green is more or less completely transmitted, so that the prevailing tint is a more or less modified green.

The second he calls the xanthophyl group. The members of this genus are characterized by being insoluble in water, but soluble in alcohol and bisulphide of carbon; the spectra show absorption at the blue, often with more or less well marked narrow bands; but the red, yellow, and yellow-green are freely transmitted, so that the general color is clear yellow or orange.

Erythrophyl is the name of a third group which includes the red coloring matters found in autumnal leaves. Usually these are soluble in water and aqueous alcohol, but not in bisulphide of carbon. Species of this genus are met with in fruits, flowers, and roots, and also in several different sorts of leaves.

A fourth group, to which from the predominance of a goldenyellow tint Dr. Sorby gives the name of chrysophyl, also contains several species. These vary somewhat in tint, from a little more yellow to a little more red than yellow ochre. They are soluble in water and aqueous alcohol, but not in bisulphide of carbon. To a fifth group, from the prevailing color being brown, he gives the name phaiophyl. Many of the tints in this group arise from the oxidation of chrysophyl. They are sparingly soluble in water, but dissolve best in a mixture of alcohol and acid.