MADDER.

253

shades produced by the various mordants are dull and unsightly, because themordants fix not merely the alizarin and purpurin, but also the yellow andbrown colouring matters. Further, those portions of the fabric intended toremain white, become dirty, because these last-named matters adhere to suchparts. In order to utilise all the disposable colouring matter present in themadder, it is requisite to raise the temperature of the bath gradually to theboiling-point. Without this precaution a serious loss would ensue. In additionto these disadvantages of madder, which refer especially to printing calico andsilk, not to dyeing wool a uniform colour, it is not possible to utilise all thecolouring matters contained in the root. Nearly half the colouring matter iscombined with lime-salts and with woody fibre so intimately that it cannot beunited with the mordants of the fabric. In consequence the spentdye-material still contains alizarin, which can be utilised, as we shallshow below in treating of garanceux. Since the beginning of this centurymany proposals and attempts have been made to obtain the colouringprinciples contained in madder in a higher state of purity and concentration.Up to this day no one has succeeded in entirely eliminating theuseless constituents present in madder in one operation. The dyers andprinters, moreover, exercise great caution in adopting in place of madderpreparations about which they can often judge only by somewhat prolongeduse. Garancin had to struggle for years against the scepticism of the tradebefore its use became general.

In the following pages we propose to classify the commercial preparationsof madder according to the kind of treatment to which the madder is sub-jected in their preparation :—

1. Processes which increase and concentrate the tinctorial power of themadder by the elimination of foreign substances soluble in water, or capable ofbeing rendered soluble by means which do not modify the colouring matter.

2. Processes whereby the solubility of the colouring matters in certainmenstrua is utilised to separate them from materials insoluble in the same.

3. Processes based upon the volatility of the colouring matters.

4. Treatment purely mechanical.

The reader should bear in mind that the tinctorial matters of madder formthree groups—the glucosides soluble in water; the colouring matters free butmechanically mixed with other vegetable matter; colours intimately com-bined with woody fibre. The heart of the root, a very hard tough woodymass, contains a large amount of excellent colour. The heart of the Zealandroot may be readily obtained, and after having been separately ground, yieldspure alizarin on being sublimed with care in small portions.

First Group .—

Fleur de garance, or flowers of madder, of Julian and Roquer, of Avignon.This preparation should not be confounded with the older preparation ofRobiquet, Colin, and Lagier of the same town, which is now known asgarancin. As far back as 1823, Kuhlmann came to the conclusion thatwashing madder in cold water would be an easy method of removing gum,sugar, and certain extractive and yellow colours, such as xanthin. Whenmadder, thoroughly moistened with water, is left to stand previous to beingwashed, a fermentation of a peculiar character ensues, which splits up theglucosides, and increases the tinctorial power to some extent.