3*0 An EJfay on Bleaching. 



raw cotton cloth and thread ought to be fubjected in order to 

 bleach them by this new method; and I fhall begin with 

 that of Chaptal, whofe apparatus I have before mentioned. 



The cotton, difpofed in handfuls, muft firll be impregnated 

 with a flight folution of foda rendered cauftic by lime. This 

 operation is performed in a wooden or (lone trough, in which 

 the cotton is trod down by meansof the feetcovcred with wooden 

 fhoes. When the -alkaline liquor has uniformly penetrated 

 the cotton, it is put into the boiler, and piled up on the wooden 

 grate before mentioned ; the redundant liquor runs through 

 the bars into the copper boiler, and forms a flratum of liquid, 

 •which permits the mafs to be heated without any danger of 

 burning either the cotton or the metal. . To form the alka-r 

 line ley, Alicant foda equal to a tenth of the weight of the 

 cotton fubjected to the operation is employed, and in a boiler 

 fuch as that the dimenfions of which I have given, about 

 800 pounds of cotton may be put at one time. The ley is 

 generally of two degrees by the areometer. As foon as the 

 cotton is introduced into it, and arranged in the boiler, the 

 upper aperture is fhut with its ufual covering, fcarcely any 

 opening being left, that the fleam developed by the fire may 

 affume a much more confiderable degree of heat, and react 

 with force on the cotton. When every thing is arranged, 

 the fire in the furnace is kindled, and the ley is maintained 

 in a flate of flight ebullition during thirty-fix hours. The 

 apparatus is then fuffered to cool, and the cotton being taken 

 out is carefully wafhed ; after which it is expofed on the grafs 

 for two or three days, extending it on poles in the day-time, 

 and fpreading it out on the grafs during the night. The cot- 

 ton will then have acquired a high degree of whitenefs ; and if 

 any portions of it be flill found coloured, they muft be put 

 into the boiler for a fecond operation, or be left on the grafs 

 fome days longer. Thefe fhades in bleached cotton arife, 

 in particular, from all the parts of the cotton in the firfl ope r 

 ration not having been completely and uniformly impreg- 

 nated with the ley. Thev may be owing alfo to the cotton, 

 when arranged in the boiler, having been too much accu- 

 mulated on certain points. When it is judged that the ley 

 has been exhaufted by ebullition, the boiler is opened, and 

 the dried cotton is moiflened with a new quantity of the fo- 

 lution of foda: without this precaution it would be in danger 

 of being burnt. It may be eafily conceived, by an eftimate 

 of the matters and time employed in this operation, with how 

 much faving of expenfe it is attended : cotton is bleached by 

 this method in all the manufactories of the fouth of France, 

 where it is ufed, at the low rate of two ibis per pound, 



To 



