( 9 )

IP

m

le

’g

ye

.ts

:s,

ge

d.

’g

.st

th

oy

h-

h,

ss

00

in

at

ns

is,

of

im

Is,

dy

r y

ed; a

CHAPTER I.

THE ART OF DYEING IN ITS RELATION TO CHEMISTRY.

TV/TOST operations in dyeing (the word being used here in a wider sense asapplying also to the allied arts of bleaching and printing) may be con-sidered as diredtly chemical, and the mechanical appliances as so muchapparatus intended to facilitate or regulate the chemical adtion taking placebetween the fibre, the mordant, and the colouring matter. As this adtionvaries in kind or degree for every colour produced, it may be readily grantedthat few of the arts are more intimately connedted with chemistry, or dependmore upon chemical laws, than dyeing.

Most of the recent improvements in dyeing have originated on the Continent;garancine, garanceux, with other preparations of madder, the application ofalbumen and caseine, and the introdudlion of murexide, picric acid, andmodified archil colours, are all due to France; and the best shades of the redmodification of the aniline colours have been produced in Vienna. The dis-covery of aniline dyes is, however, due to Mr. Perkin, who was the first to.manufadture them in a practicable form. Fuchsine was discovered somemonths later by Verguin, who was the adapter of the discovery of Hofmannthat bichloride of carbon gave a red colour with aniline. The number ofcolouring matters possessed by dyers is very limited; there is only one fastred upon cotton—madder, and only one fast blue—indigo. With regard to theartificial production of such substances as are formed by the vital activity ofthe plant from which madder is obtained (Rubia tinctorum), as alizarine, themost permanently active colouring principle of that substance has been producedby Messrs. Broenner and Messrs. Graebe and Liebermann. There can be littledoubt that Graebe’s alizarine will find many uses; its employment will bemerely a question of cost. Concerning the state in which the colouringmatters of madder exist in the plant, we know that alizarine is not containedas such in the root, but is formed by the adtion of acids or ferments on aglucoside whose chief properties and composition have been ascertained.That alizarine is the essential constituent of madder colours is proved by thefadt that the finest and purest madder colours (Turkey red, madder pink, andpurple) contain no other colouring matter in combination with the mordants;and there is little doubt that alizarine will form as efficient a substitute formadder as indigo has for woad. At the same time it does not follow that thqother colouring matters of madder are useless.