CALICO-PRINTING 

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Dlll^TJWDOT&l 



was only -within a few years that 

 chemical science has shown the 

 wisdom, if not the necessity, of the 

 system. Some dye-stuffs, and es- 

 pecially madder, do not contain their 

 colouring matter ready formed in 

 considerable quantity, but contain a 

 colour-forming principle, which is 

 acted on by nitrogenous ferment also 

 present, whose activity is unlocked 

 by the solution in water, and by 

 the aid of which the colour-forming 

 principle becomes decomposed into 

 true colouring matter and some 

 other substance. The newly-formed 

 colouring matter is assimilated by 

 the mordant nearly as fast as pro- 

 duced. As with most ferments, the 

 temperature of boiling water de- 

 stroys the ferments in dye-stuffs, and 

 a very inferior result would in many 

 cases be produced, were a boiling 

 heat to be given during the first 

 periods of dyeing. See MADDER. 

 With the colouring matters of dye- 

 stuffs properly formed and separated 

 from woody fibre, these precautions 

 are generally unnecessary, as is 

 explained when treating of madder 

 extract and alizarine. When the 

 dyeing is finished, the steam is shut 

 off, the knots untied, and the pieces 

 pulled over into a pit of water 



379 



