BLEACHING. 



mersed in this for about twenty minutes, heated to 

 56 Fahr. It is then taken out, drained, and 

 rinsed in running water ; then put into the bath of 

 urine, and washed again. This is sometimes re- 

 peated a third time, and sometimes scouring with 

 soap is used. 



Fulling the cloth adds also to its whiteness. 

 Fulling is a species of scouring with a particular 

 kind of earth called fuller's earth. It effectually 

 removes all grease, from the chemical affinity 

 existing between the alumina contained in the 

 fuller's earth and the oil of the cloth ; and thus dis- 

 poses the fibres to be entangled and matted toge- 

 ther in the subsequent process of milling, employed 

 to thicken the cloth, and render it stronger and 

 firmer. 



Scouring entirely with soap is preferred when 

 the articles are valuable. 



Sulphureous acid is also used for giving the last 

 degree of whiteness. 



Sulphuring is performed in the following man- 

 ner. The articles to be whitened are suspended 

 iiopn poles across a chamber, constructed so as 

 to be perfectly close. Into this chamber is pre- 

 viously put a quantity of sulphur in dishes. When 

 the cloth is in, the sulphur is set fire to, and the 

 doors of the chamber are accurately shut, and all 

 the interstices carefully stopt up, so as to exclude 

 entirely the atmospheric air. 



The combustion of the sulphur produces a va- 

 pour which is the sulphureous acid; this destroys 

 the colouring matter of the wool, which is conse- 

 quently rendered white. The time necessary for 

 this process varies from six to twenty-four hours. 

 The cloth is left in the chamber for some time 

 after the combustion of the sulphur has ceased j it 



