DYEING AND CALICO PRINTING.

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obtained from madder is due to amylic and other homologous alcohols,and partly to the existence of a peculiar camphor-like substance presentin madder, and known as camphor of madder. This substance, accordingto the researches of M. Jean Jean, is isomeric with the Borneo camphor(ChjHxsO). The camphor from madder can be obtained in small hex-agonal prismatic crystals; it is hardly soluble in water, readily so inacetic acid, alcohol, and ether, and turns the plane of polarisation to theleft. The great advantage of Jleur de garance, or rather its superiority tomadder, especially for printing, is owing to the purity and great beauty of theviolet tints produced by this material, with equal fastness but superior bril-liance. The simple reason is, that by the operation to which madder is sub-jected, to produce bloom of madder, all the soluble, mucilaginous, saccharine,and brownish-coloured matters are removed from that substance ; and sincethese substances interfere with iron mordants, and thereby deteriorate theviolets, it is clear that flowers or bloom of madder yield a superior violet.

With alumina and iron mordants bloom of madder produces deeper shadesthan madder. This seems to be due to the solvent adtion exercised upon themordants by the substances soluble in water present in madder; and the.degree of this adtion may be judged from the fadl that when bloom of madderis used the same intensity of colour is produced as with madder, with mor-dants of from fifteen to twenty times less strength than madder would require.The rose-red and red shades produced by fteur de garance are quite as beau-tiful as those which madder gives, and have, as compared with madder, theadvantage of greater fastness. The portions of the fabric intended to remainwhite are less soiled when bloom of madder is used than is the case whenmadder is employed. There is an advantage gained, also, in respedt ofclearing and soaping. The other advantages of bloom of madder are—greater regularity of dyeing; less difficulty in the management of the dye-bath ; the possibility of adding a fresh portion of bloom to the bath when itappears exhausted, which cannot be done when crude madder is used ; andthe perfect exhaustion of all colouring matter from the bath. It should beunderstood, however, that what is here said relates exclusively to calico-printing,—that is to say, to the passing of calicoes, muslins, and such-likefabrics, upon which designs have been printed by rollers supplied with therequisite mordants, through the dye-baths. Bloom of madder is not used indyeing woollen fabrics to which a uniform shade is to be given, neither forTurkey-red. Bloom of madder is preferable, since for equal weights it con-tains twice as much colouring matter as madder, and it has the decidedadvantage that it is less sensitive to damp warehouses, and does not, likemadder, become spoiled by age.

The length of time madder can be kept and preserve its full vigour differsfor different kinds of madder. Counting from the moment the ground materialis packed in casks, Avignon madder and the produce of Southern Europe

separated from the liquid by careful distillation in the water-bath, and purified by combinationwith ammonia. If the impure madder-spirit is agitated with sodium amalgam, perfectly purealcohol is obtained, since the aldehyde is thus hydrogenised to alcohol, the acetic ether beingalso decomposed with formation of alcohol and acetate of soda. The opinion has been enter-tained that there is a relation between the amount of sugar present in madder and the amountof the tindtosial principles.