MADDER.

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and boiling the residue again with a fresh quantity of the same acid. Thesesolutions deposit, on cooling, an orange-coloured flocculent matter, whilesome remains in solution, which is best precipitated by means of chloride ofsodium. . These sediments are carefully colle&ed on a small dried and taredfilter, washed with distilled water, carefully dried, and weighed.

By means of this process M. Schlumberger has obtained from 100 grms. ofgood madder (Avignon, Alsace, and Zealand) from 4*1 to 4*2 grms. of colouringmatter. Inferior kinds—that is to say, second quality of the same origin—gave from rg to 2*7 grms., while freshly-ground madder yielded from 3*8 to4*2 grms. per cent, because, as regards the latter, the boiling with acetic acidhas the effett of splitting up the glucosides, thereby making them equally richin colouring matter as old madder.

The following mineral substances have been occasionally used to adulteratemadder:—Ground-up red bricks, red and yellow ochres, yellow sand, andnative coloured clays. Among organic substances the following have beensometimes used :—Sawdust of dark coloured woods, ground-up almond-shells,bran, fir-wood bark, logwood, santal wood, sapan wood, Brazil wood : asregards the mineral matters these may be readily enough detected, by theincineration of madder in a platinum crucible. It is best to take for thatpurpose from 5 to 10 grms., and to bear in mind that the quantity of ash(mineral matter) naturally present in madder varies from 5 to 9 per cent; inlow class Mull madders it may reach 50. The qualitative testing of the ashwill suffice to detedt any fraudulent admixture.

As regards the adulteration with organic substances, we quote M. Pernod’splan for discovering their presence :—A piece of white paper is dipped for aminute or so in a weak aqueous solution of bichloride of tin ; the sheet isplaced on a plate glass, or on a clean porcelain dish, and by means of a finegauze sieve a very small quantity of the pulverised madder is scattered onthe surface. After the lapse of about half an hour every portion of the paperwhere a particle of the dye-wood has fallen will exhibit the followingcolourations :—

For Brazil wood .. .. .. Carmine-red specks.

,, Logwood .Violet-coloured spots.

„ Fustic .Yellow-coloured spots.

,, Genuine madder .. .. Faint yellow colouration.

If astringent substances have been added these may be readily detected bymeans of a sheet of test-paper impregnated with a mixture of proto- and per-salts of iron, and moistened with alcohol. This paper, strewed over with thesuspected madder in the manner as above, will, in case of adulteration, exhibitblackish-blue specks wherever any astringent matter has fallen. Pure madderyields in this instance only a bright brown colouration. The presence offoreign dye-woods in madder can also be ascertained by testing a hot filteredsolution of madder with bichloride of tin or a per-salt of iron.

Use and Application made of Madder, and its Preparations forDyeing Purposes.

The red colouring substances present in madder—that is to say, those whichyield red colours with mordants of alumina—are its only really useful consti-tuents. As regards the yellow and brownish matters, they only serve to

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