Remarks upon Bleaching, 65 



prejudices inseperable from long established habits, and 

 practical men though strongly wedded to their own meth- 

 ods of workmg, and sufficiently jealous of projected improve- 

 ments, have yielded reluctantly to a conviction of their util- 

 ity. It is presumed that the usual method of chemical 

 bleaching as now practised both in Europe, and th(i United 

 States of America is too well known, to require a particular 

 description. In that method, there appears to me to be a 

 fundamental error in the alternate use of hot and cold li- 

 quors. It is evident that a heated solution of alkali opens 

 and expands the fibres of linen submitted to its action, 

 and thus affords an opportunity for the alkali to act up- 

 on its coloring matter, and to increase its solubility. But 

 the second step in the ordinary process of bleaching, coun- 

 teracts the first. The linen is taken hot from the bucking 

 tub, and immediately thrown into coZ^ water, for the purpose 

 of being washed. The fibres of linen collapse ; the coloring 

 matter is condensed, and its affinity for the linen is restored, 

 which is manifestly the reverse of the object intended to be 

 gained by the process. — If the rinsing water be of the same 

 temperature as the alkaline liquor, this re-action is prevented. 



2dly. From this washing in cold water, the linen, after hav- 

 ing been bucked a sufficient number of times, and exposed 

 for months to the air in the fields, comes, in due course of 

 time, to its second stage of operation. 



The linen in large quantities, is immersed in vats of cold 

 chloride of lime, in a quiescent state, and the bleaching prop- 

 erties of the liquor act upon it imperfectly and unequally, in 

 consequence of the dense mass of linen, and the frigidity of 

 the medium through which it has to act. 



If the linen were put into the bleaching liquor moderately 

 warmed, confined so as to prevent the escape of gaseous 

 vapours, and then set into regular and constant motion, these 

 objections would be obviated ; the effect of the warm liquor 

 would be uniform and active, which can never be the fact 

 while it is cold, and in a state of rest. 



What I have remarked concerning the manner of using 

 alkaline and chloruretted liquors, applies with equal truth to 

 the use of acidulated water in the third stage of bleaching. 



3dly. The third most important point to be considered in 

 the process of bleaching, is the degree of heat to which the 

 linen is subjected. 



Vol. XV.— No. 1. 9 



