2$6 i EJJay on Bleaching. 



fpreacl out on the grafs ; and this operation was feveral times 

 repeated until the required whitenefs was obtained. It was 

 #ill aecefiary to wind it through ibapy water, not onlv to give 

 it toftnefb and pliability, but to bleach completely the borders, 

 which oppofe the longeft refiftance. 



It was brought to its ultimate (late of whitenefs by draw- 

 ing it through whey or diluted fulphuric acid. By this (hort 

 description it may be (een that a confiderable time was rie- 

 eeffary before the abforption of oxygen could take place : to 

 frafren this operation of nature appeared impofiible, until 

 modern chemiftry had demonftrated that oxygen, folidified 

 in various bodies, might be extracted and combined with 

 water, to be afterwards applied to fubftances where its influ- 

 ence might be neceflary. 



Bleaching hy Water alone. 



I have already obferved that, during the fermentation that 

 takes place in the vats in which cloth is immerfed to free it 

 from the drefling, the fibres affiime the firtt tint of whitenefs. 

 It had been before remarked that the percuffion of {tampers 

 in paper manufactories bleached, in fome degree, the pulp 

 impregnated with watery it was known that, by fuffering 

 hemp and flax to ferment a very long time, a greater degree 

 erf whitenefs was obtained, but always at the expenfe of the 

 fibrous tifTue, deftroved by too long maceration. Taking 

 advantage of thefe obfervations, Brafle, an artift of Amiens, 

 found means to bleach hemp and linen by the action of water 

 alone. 



When the hemp was pulled^ he watered it a little longer 

 than ufual, having previoufly cut off the roots by laving the 

 Italks on a board furnifhed with an inftrument deflined for 

 that purpofe. When the cortical tifTue was attacked, and 

 deftrOyed by the putrid fermentation, he removed the hemp 

 from the water, and, by drawing it through a kind of heckle 

 cr comb, completely feparated the fibrous tifTue, w^hich, on 

 account of its parallelifm, was not hurt by the teeth of the 

 inftrument ; while the reticular tiffue of the bark or exterior 

 covering, already half putrid, thick on the points, and readily 

 differed itlelf to be feparated from the hemp. During thwi ope- 

 ration the hemp was immerfed fucceffively in water, between 

 each ftroke of the heckle, to facilitate the removal of the green 

 matter above the bark. The whitenefs which hemp afTumes 

 bv this (ingle operation can hardly be conceived : it acquires 

 a fplendour and brilliancy which can never be communicated 

 to it by the ufual procefTes, but its flrength is alfo diminished 

 as well as the product by the too great progrefs of the-fer- 

 8 i mentation ; 



