An Ejfoy on Bleaching. %6l 



tered through a bafket filled with lime ; it was then evapo* 

 rated to drynefs, and the refiduum was calcined in a rever- 

 berating furnace. When foda of a fuperior quality is re- 

 quired, the warning and calcination muft be repeated. 



Dize and Le Blanc decompofed the fulphate of foda, by 

 means of the carbonate of lime, in order to neutralize the 

 alkali, by faturating it, at a very high temperature, with 

 carbonic acid. Their procefs confifts in taking two parts 

 of fulphate of foda, dried to deprive it of its water of cryv 

 ftallization, two parts of well ground chalk (carbonate 

 of lime), and one part of charcoal powder, mixing them 

 well in a muffled mortar, and then bringing the mix- 

 ture to a white heat in a reverberating Furnace : when 

 the matter is fufed it is ftirred till the fulphur is con- 

 fumed, and the ebullition and the jet of the flame pro- 

 duced by the hydrogen gas have ceafed to appear. It is then 

 taken from the furnace, and it may be lixiviated to obtain 

 the foda very pure. In whatever manner the fulphate is de- 

 compofed, this objecT: merits the greateft attention at bleach- 

 fields on account of the confiderable degree of ceconomy 

 which remits from the different manipulations. The ley of 

 oxygenated muriatic acid will be obtained at little or no ex- 

 p.ente by bleachers, when they ferioufly fet about extracting 

 the foda from the fulphate formed during the diftillation. 



In whatever manner the muriatic acid gas may be diftilled, 

 the great object is to faturate the water with this aerifomi 

 fluid. Its action in bleaching is always ftronger when em- 

 ployed alone than when in the ftate'of combination with falts 

 or earths, as in the fubfequent operations of which I am 

 about to fpeak. The volatility of the acid, however, is fuch, 

 and the lofs of the gas fo enormous, rhat, when the thread or 

 cloth is immerfed, there is diifipaled of it a quantity which 

 may be eftimated at about a third, at leaft, of the whole gas. 

 The mixture of potafh, indeed, renders the liquor inodorous; 

 but befides that this fait is expenfive, it greatly weakens the 

 deterfive quality of the liquor. 



Rupp, of Mancheiter, has invented an apparatus for bleach- 

 ing cloth exceedingly fimple in its conitniclion, of I'm all ex- 

 penfe, and which contains the liquor in fuch a manner as 

 to prevent the efcape of the oxygenated muriatic acid gas. 

 A confederation of no lefs importance in the arrangement of 

 this apparatus is, the lmpombiljty of the vapour injuriug the 

 health of the workmen, I have witneffed, in a very large 

 manufactory near Paris, the dreadful fuflferings to which 

 thefe unfortunate people were expofed by thele fuffocating 

 vapours. I have fceii them rolling on the ground through 



R 3 pain^ 



