170 BLEACHING. 



cloth is first immersed in weak caustic alcaline 

 liquor, and placed over a chamber constructed over 

 a boiler, into which is put the alcaline ley which is 

 to be raised into steam. After the fire has been 

 lighted, and the cloth lias remained exposed to the 

 action of the steam for a sufiicient length of time, 

 it is taken out, and immersed in the oxygenated 

 muriate of lime, and afterwards exposed for two 

 or three days on the grass. 



This operation, which is very expeditious, is suf- 

 ficient for cotton ; but if linen-cloth should still 

 retain a yellow tint, a second alcaline vapour-bath, 

 and two or three days exposure on the grass, will 

 be sufficient to give them the necessary degree of 

 whiteness. 



Bleaching of Cotton. 



Cotton is a vegetable substance, and the pro- 

 duction of a shrub that grows only in warm climates. 

 It is a fine downy substance, in which the seeds of 

 the plant are inclosed. Cotton, in its natural state, 

 is generally of a dirty yellow, and opaque, being- 

 covered with a colouring matter of an unctuous 

 nature ; when this is removed, it is white and 

 transparent. 



Cotton is easier to bleach than linen. The 

 colouring-matter is dissolved by the action of alca- 

 line leys and washing. Sometimes the oxymuri- 

 atic acid is also used to expedite the process. 

 Steeping in diluted sulphuric acid, is also used to 

 dissolve the earthy matter that always remains after 

 the immersion in alcaline ley; and as cotton is not 

 so easily injured by acids as flax, more use is made 

 of the acid than in the bleaching of linen. The 



