Madder is used for dyeing woollen, silk, and also cotton goods, and the color is very lasting, and resists the action of the air and sun. Within a few years, a method has been discovered of rendering the red exceedingly brilliant and ap proaching to purple. It also forms a tint for several other shades of color : it has the curious properties of tinging the bones red of those animals which feed upon the roots.
It appears that madder may be consid ered as composed of two coloring sub stances, one of which is dun (tawny), and the other is red. Both of these sub stances may combine with the stuff. It is of consequence, however, to fix only the red part. The dun portion appears to be more soluble, but its fixity on stuffs may possibly be increased by the affinity which it has for the red portion.
The different additions made to mad der, and the multiplied processes to which it is sometimes exposed, havepro bably this separation for their chief ob ject.
The red portion of madder is soluble, but in small quantity, in water. Hence but a limited concentration can be given to its solution. If the portion of this substance be too much increased, so far from obtaining a greater effect, we merely augment the proportion of the dun part, which is the more soluble of the two. In consequence of the Indus trielle of Mulhausen having offered in the year 1826 large premiums to the authors of the best analytical investigation of madder, eight memoirs were transmitted to it in the year 1827. They were ex amined with the greatest care by a com mittee consisting of able scientific and practical men. None of the competitors however fulfilled the conditions of the Rrogramme issued by the society ; but four of them received a tribute of esteem and gratitude from it ; MM. Robiquet and Colin at Paris, Kuhlmann at Lille, and Houton-Libillardiere. Fresh pre miums were offered for next year, to the amount of 2000 francs.
Every real discovery made concerning this precious root, would be of vast con sequence to dyers and calico-printers. Both M. Kuhlmann, and Robiquet and Colin, conceived that they had discovered a new principle in madder, to which they gave the name alizarine. The latter two chemists treated the powdered madder with sulphuric acid, taking care to let it heat as little as possible. By this action the whole is carbonized, except perhaps the red matter. The charcoal this ob
tained is pulverized, mixed with water, thrown upon a filter, and well washed in the cold. It is next dried, ground, and diffused through fifty parts of water, con taining six parts of alum. This mixture is then boiled for one quarter of an hour, and thrown upon a filter cloth while boil ing hot. The residuum is once more treated with a little warm alum water. The two liquors are to be mixed, and one part of sulphuric acid poured into them ; when they are allowed to cool with occa sional agitation. Flocks now make their appearance ; the clear liquid is decanted, and the grounds are thrown upon a filter. The precipitate is to be washed, first with acidulated water, then with pure water, and dried, when the coloring matter is obtained in a red or purple state. This purple substance, when heated dry, gives out alizarine, and an empyreumatic oil, having an odor of animal matter ; while a charcoally matter remains.
M. Dan. Ktechlin, the justly celebrated calico printer of Mulhausen, has no faith in alizarine as the dyeing principle of madder ; and thinks moreover that, were it of value, it could not be extracted on the great scale, on account of the destruc tive heat which would result from the acid acting upon a considerable body of the ground madder. Their alizarine is not a uniform substance, as it ought to be, if a proximate principle ; for samples of it obtained in different repetitions of the process have produced very variable effects in dyeing. The madders of Avig non, though richer in color than those of Alsace afford however little or no aliza rine. In fact, purpurine, the crude sub stance from which they profess to extract alizarine, is a richer dye than this pure substance itself.
Madder contains so beautiful and so fast a color, that it has become of almost universal employment in dyeing; but that color is accompanied with so many other substances which mask and de grade it, that it can be brought out and fixed only after a series of operations more or less difficult and precarious. This dye is besides so little soluble, that much of it is thrown away in the dye house ; the portion supposed to be ex hausted being often as rich as other fresh madder ; hence it would be a most valu able improvement in this elegant art to insulate this tinctorial body, and make it a new product of manufacture.