292 Cellulose 



reagent employed in the treatment ; and, secondly, by physical 

 changes in the cotton itself or its non-cellulose constituents. 

 In the alkaline treatments of cotton it is of importance that 

 the action of the alkali, water, and heat should be as nearly 

 as possible equal and simultaneous throughout the mass. The 

 advance of the caustic alkali process over the successive treat- 

 ments with lime and soda ash of the older methods consists 

 chiefly in this, that by the more rapid action of the more 

 powerful alkali, secondary changes of the more oxidisable non- 

 cellulose constituents are reduced to a minimum ; and these 

 are dissolved away by a single operation, with a minimum 

 residue of products to be removed in the bleaching process 

 proper. In the ordinary processes of bleaching, the result 

 attained is simply measured by the appearance of the cloth. 

 The printer, however, requires something more than a good 

 white. The operations of calico printing in many cases involve 

 a dyeing process, not of the whole cloth, but of the design or 

 pattern printed with suitable mordants, the cloth itself being 

 required to resist the colouring matter of the dye bath. Many 

 * market bleaches ' are therefore very inferior in point of purity 

 of the cellulose to the * madder bleach ' of the printer, and 

 will dye up with alizarin and similar colouring matters, which 

 the latter will resist under the same conditions. It is in regard 

 to this important distinction, and the further refinement of the 

 bleaching process for the * madder bleach,' that progress con- 

 tinues to be made. 



Linen bleaching. The full bleach of flax goods, which 

 consists in the isolation of the pure cellulose, is a much more 

 complicated process than the bleaching of cotton-cloth, though 

 based upon identical principles, and involving for the most part 

 precisely similar methods. 



The proportion of non-cellulose constituents in flax is very 

 high, varying from 20-35 P- ct - f the weight of the fibre, 



