I£P METHOD OF BLEACHING PAPER, 



fucceflion to different lees, to batlis of the bleaching liquor,, 

 and fulphuric acid pointed out in his memoir. Berthollet had 

 fhewn, and we were alfo convinced by our own experience, 

 that the gas is lefs confined in the fimple fluid, prepared with- 

 out addition of fixed alkali, than it is in that which contains 

 potafh or foda; and that it is confequently more difpofed to 



Difficulty of feparate and enter into new combinations. We therefore at 

 ufingth C bleach. firftmadeufe f ^ f , jj fc fc the workmen f oon 



ing liquor with- . r . * / 



out alkali. exhibited a ftrong repugnance to its ufe on account of the 



fumes it emits, which are extremely inconvenient, even when 

 chalk is diffufed in the liquor. This inconvenience forced us 

 to abandon it, though with regret. This facrifice was fq 

 much the more confiderable, as it occafioned a lofs of time, 

 and confiderable increafe of expence. We decided that we 

 would receive the gas in a folution of potafh ; but as the dofes 

 in which this alkali may be ufed have limits of great extent, 

 we endeavoured to keep as near as poffible to that prepara- 

 tion which is fufficient to prevent the fpontaneous difengage- 

 ment of the gas, and by that means caufe the liquor to lofe the 

 odour we were defirous of avoiding. This dofe was 5 kilor 

 grams of potafh to 100 litres of water, (11 pounds avoirdu-r 

 poife, to 2 If ale gallons.) 

 The rags became The rags bleached in this manner became of the moft bril- 

 wh^pened b by liant white ' Neverthelefs, a part of this perfeftion difap- 

 the mill were peared, when the rag was converted into pafte, and that pafte 

 lefs fo. j nto p a p er# i s was ea fy to difcover the caufe ; namely, that 



the interior parts of the thread in the rag were lefs expofed 

 to the aclion of the liquor than thofe at the furface. This mo- 

 tive determined us to abandon the bleaching of the rags, and 

 to operate upon the pafte itfelf. 

 The parte wat We were here oppofed by new obftacles. When the rag 

 is converted into a pafte proper to be worked, its coherence 

 is fuch that it fettles, and no longer permits the lees and baths 

 of the bleaching liquor to penetrate through all its parts, in 

 confequence of which property the paper was found to have 

 veins and different fhades of colour. We remedied this incon- 

 venience, by taking the matter in a mean ftate between the 

 rag and the pafte proper to be converted into fheets of paper. 

 in Its half pre- We fucceeded in this refpect by deftroying the texture of the 

 pared ftate. under the firft cylinder fo as to feparate its fibres, an ope- 



ration which ufually lafted two hours for a pile of 50 kilograms. 



rThus 



1 



