MADDER.

233

as admitted by French authorities. There exists a considerable differencebetween the fresh root and the commercial madder, both in appearance andproperties. When the recent root is squeezed an acid yellow liquid oozes outwhich turns red on exposure to the air. This fluid, when applied to cottonprepared with acetate of alumina, yields a bright red dye, which turns a dullrose-colour when soaped. The entire fresh root and its different parts yieldduller and more fugitive shades than does the dried root. When a thin sectionof the fresh root is viewed under the microscope, not a trace of any separatecolouring matter is seen. According to the researches of M. Decaisne thecells of the fresh root are filled with a yellow liquid, the deeper in colour asthe plant is more mature. This liquid becomes converted into an insolublered principle on contact with the air. It is a strange fact that the fresh madderhas never been the subject of any other than chemico-microscopic research,on a very limited scale. After being ground the constituents of the root un-dergo important modifications, which go on even after it has been stronglycompressed into the casks. We shall return to this subject after having con-sidered the composition of madder.*

Kcechlin found in 100 parts dry commercial madderf 55 parts of mattersoluble in cold water; 3 parts soluble in boiling water, including the colouringmatter; 1*5 soluble in alcohol; and 38 insoluble in the above liquids.

a. Substances Soluble in Cold Water.—

1. Glucose , or at least a saccharine substance capable of fermentation,

and of yielding an abundant precipitate with Fehling’s test.

2. Cane-sugar , found at least in the Zealand and Alsace varieties. The

amount varies with the age of the root and the circumstances of itsgrowth, but cannot be estimated at less than from 13 to 16 per cent.Part of the glucose pre-exists In the root, but part, as is evident fromthe researches of Dr. Schunck, is formed by the splitting up of theglucosides which the root contains.

Neither of these sugars is of any use in dyeing. Both are sometimesutilised in the shape of alcohol, formed during the manufacture of flowers ofmadder.

3. Gum and Mucilage— The latter appears to be a pectate of potash. The

cold aqueous infusion of ground madder from Zealand and Alsaceoften becomes a complete jelly from the abundance of this substance.

4. The aqueous solution of madder, like that of other vegetables,

contains albumen.

5. A peculiar nitrogenous principle precipitable by alcohol and acting the

part of a ferment. It breaks up the colouring glucosides, and con-verts pectin into pectic acid (erythrozym).

* In order to decide the question as to the effect of heat in drying madder in Zealand, aquantity of fresh root—about 1 kilo.—was carefully cleansed from earth, and placed, unbroken,under a bell-glass over sulphuric acid. The air of the glass was exhausted, and the pumpworked daily for half an hour, to remove any air or vapour given off from the roots. Afterabout three weeks the roots were quite dry, and, on being ground up, the madder was notfound to differ from that prepared in the ordinary way. Its colour was paler, but its tinctorialpower was at least equal.

t Madder is very hygroscopic, and may contain 17 per cent of water without feeling damp.