An EJfiiy on Bleaching. 99 



Of the Bleaching of Wool. 



Tn the preliminary operations to which wool is fubje&edj 

 it is cuftomary to leave a little of its greafe to fecure it from 

 infects. Wool is often freed from the greafe by the farmers 

 when they with to fell it at a high price; but in the fubfe* 

 quent manipulations it is greafed or oiled before it is combed, 

 fpun, &c; and as this fat matter attracts dull, it dirties and 

 thickens the (kin's. The firft kind of bleaching to which 

 wool is fubjected, is to free it from thefe impurities. This 

 operation is called fcouring. In manufactories it is gene- 

 rally performed by means of an ammoniacal ley, formed of 

 five meafures of river water and one of ftale urine ; the wool 

 is immerfed for about twenty minutes in a bath of this mix- 

 ture heated to fifty-fix degrees; it is then taken out, differed 

 to drain, and then rinfed in running water: this manipula* 

 tion foftens the wool, and gives it the firft degree of white* 

 nefs ; it is repeated a fecond, and even a third time, after 

 which the wool is fit to be employed. In fome places fcour* 

 inn is performed with water (lightly impregnated with foap; 

 and, indeed, for valuable articles this proeefs is preferable^ 

 but it is too expenflve for articles of lefs value. 



Fulling the cloth adds ftill to the whitenefs, and if a new 

 degree be neceflary it muft be procured by the action of the 

 fulphurous acid ; that is to fay, of the fumes of fulphur in a 

 ftate of combultion, or that acid vapour condenfed and com* 

 bincd with water. 



Sulphuring is generally performed in an arched or very 

 clofe chamber, conftrucled in fuch a manner that the arti* 

 cles to be expofed to the action of the fulphur can be fuf- 

 pended on poles. The chamber being filled, a certain quan* 

 titv of fulphur is put in a ftate of combultion on flat difhes 

 having a large furface with verv little depth : the entrance is 

 ipecdily fhut, and all the interftices around the door are care- 

 fully (topped to prevent the accefs of the atmofpheric air. 

 The acid generated by the combuilion of the fulphur pene- 

 trates the ftuffs, attacks the colouring matter, deftroys it, and 

 effects the bleaching;. The ftuffs are left in the (love fome 

 time after the deflagration has ceaied. This time varies from 

 fix to twentv-four hours. They are then taken out, and 

 made to pals through a flight warning with fgap, to remove 

 ithe roughnefs they have acquired by the action of the acid, 

 and to give them the neceflary foftnefs. 



A fimple defcripdon of this proeefs (hows how imperfect 

 it is. Ai firft the acid of the fulphur acts only on the fur- 

 faces, and does not penetrate them. This aerial immerfion 



G a is 



