160 BLEACHING, BLUEING, STARCHING 



to furnish hydrogen for combination with the chlorine, and no 

 oxygen is set free. 



Bleaching powder. Chlorine gas has a very injurious 

 effect on the human body, and cannot be used directly 

 as a bleaching agent. It attacks the mucous membrane 

 of the nose and lungs, and produces the effect of a severe 

 coUd or catarrh, and when inhaled, causes death. But certain 

 compounds of chlorine are harmless, and can be used for de- 

 stroying either natural or artificial dyes. One of these com- 

 pounds, namely chloride of lime, is one of the most impor- 

 tant bleaching agents of commerce. It comes in the form 

 of powder, which can be dissolved in water to form the 

 bleaching solution in which the colored fabrics are immersed. 

 But fabrics immersed in a bleaching powder solution do not 

 lose their color as would naturally be expected. The reason 

 for this is that the chlorine gas is not free to do its work, but 

 is restricted by its combination with the other substances. By 

 experiment it has been found that the addition to the bleach- 

 ing solution of an acid, such as vinegar or lemon juice or sul- 

 phuric acid, causes the liberation of the chlorine. The chlorine 

 thus set free reacts with the water and liberates oxygen ; this 

 in turn destroys the coloring matter in the fibers, and transforms 

 the material into a bleached product. 



The acid used to liberate the chlorine from the bleaching 

 powder, and the chlorine also, rot materials with which they 

 remain in contact for any length of time. For this reason, 

 fabrics should be removed from the bleaching solution as 

 soon as possible, and should then be rinsed in some solution, 

 such as ammonia, which is capable of neutralizing the harm- 

 ful substances. Finally the fabric should be thoroughly rinsed 

 in water in order that all foreign matter may be removed. 

 The reason home bleaching is so seldom satisfactory is that 

 most amateurs fail to realize the necessity of immediate neutrali- 



