WOOL AND SILK BLEACHING 



zation and rinsing, and allow the fabric to remain too long in 

 the bleaching solution, and allow it to dry with traces of the 

 bleaching substances present in the fibers. Material treated 

 in this way is thoroughly bleached, but is at the same time 

 rotten and worthless. Chloride of lime is frequently used in 

 laundry work ; the clothes are whiter than when cleaned with 

 soap and simple washing powders, but they soon wear out unless 

 the precaution has been taken to add an " antichlor " or neutral- 

 izer to the bleaching solution. 



Commercial bleaching. In commercial bleaching the 

 material to be bleached is first moistened with a very weak 

 solution of sulphuric acid or hydrochloric acid, and is then 



FIG. 60. The material to be bleached is drawn through an acid a, then through 

 a bleaching solution b, and finally through a neutralizing solution c. 



immersed in the bleaching powder solution. As the moist 

 material is drawn through the bleaching solution, the acid on 

 the fabric acts upon the solution and releases chlorine. The 

 chlorine liberates oxygen from the water. The oxygen in 

 turn attacks the coloring matter and destroys it. 



The bleached material is then immersed in a neutralizing 

 bath and is finally rinsed thoroughly in water. Strips of cotton 

 or linen many miles long are drawn by machinery into and out 

 of the various solutions (Fig. 60), are then passed over press- 

 ing rollers, and emerge snow white, ready to be dyed or to be 

 used as white fabric. 



Wool and silk bleaching. Animal fibers like silk, wool, 

 and feathers, and some vegetable fibers like straw, cannot be 

 bleached by means of chlorine, because it attacks not only the 



