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DYEING AND CALICO PRINTING.

will take up the mordant, and leave the colouring matter loosely attached tothe cloth. The acid can be removed by washing, and then the colour extractedby spirits of wine. This colouring matter may have been subjected to thecontact of acid quite as strong as that used in making garancin (and even farstronger), and for as great a length of time, but it is not affeCted like thecolouring matters in garancin. It can still dye up fast reds, pinks, andpurples, upon mordanted cloth; yielding colours which are not injured, butimproved, by soaping and clearing. The question arises, Why should acidsaCt so differently in one case and in the other ? It can be easily understoodhow great an advantage it would be if garancin gave as fast colours as madder.This result may perhaps be accomplished when we have a more accurateknowledge of the aCtion of acids upon madder.

In the beginning of 1870 a brief private communication was receivedby us from the chemist in charge of the four largest garancin works inHolland. The manufacture of garancin from Zealand madder, made by theold-fashioned plan, is attended with some practical difficulties, to removewhich the aid of science has been called in. Researches have been made—not only by the chemist just mentioned, but also by Prof. Mulder, ofUtrecht, and others—which show that the garancin so prepared is as goodfor all practical purposes as the best madder, and the colours are equally fast,while the dyeing operations are easier and take less time in clearing; theprocess, however, is kept a trade secret. We are informed that this garancinalso dyes Turkey red rapidly.

The Avignon garancin usually met with in commerce is a finely pulverisedpowder, of a more or less deep brown colour. The ligneous matter is not atall carbonised, as can be proved by exhausting the substance successively withsoda and acid, when a residue is obtained free from colouring matters, hardlyany deeper in colour than fleur de garance. 100 grms. of garancin yieldedfrom 16 to 17 grms. of peCtic acid, the greater part of which is in a free state,while a small portion is combined with lime. At the same time 48 grms. ofligneous matter (woody fibre) is obtained. Since 100 grms. of madder(Avignon) containing 20 of ligneous matter yield about 40 grms. of garancin,it is clear that the woody fibre is very little aCted upon by the treatment withsulphuric acid.

The tinctorial value of garancin of good quality is from 4 to 4-5—evensometimes 5—times greater than that of the madder it is obtained from ;100 parts of madder, by weight, yield from 36 to 40 parts of garancin.

While garancin has its decided advantage, especially as regards the greatsaving of time, expense, and labour in the production of coloured designs forprinting, it cannot be used as a substitute for madder. Garancin colours areless fast and solid than those from madder with the same mordants, and someof the shades are always decidedly inferior to madder shades of the same kind.It has been proposed to remedy this defect by the addition of a small quantityof chalk to the garancin bath, but this remedy is attended with a real loss ofwhat was gained by the previous treatment of the dye-stuff with acid. Thegenerally prevailing opinion on this practical inconvenience is, that it is due tothe presence of a small quantity of ligno-sulphuric acid* which is intimately

* There have been numerous proposals made, and a large number of Patents have been takenout, to remove from garancin all the sulphuric acid, but the application of alkalies—even in the