METHOD OF BLEACHING PAPLR. 1 19 



ftarch. And the lute is left to dry from fix to twelve hours, 

 after which the fire is lighted in the furnaces. 



The procefs of diftillation laiis from ten to twelve hours. 

 When it is finiflied the tubes are unluted, the fire extinguished, 

 and the mattrafes fettered to cool in their fand beds, till the 

 temperature of thefe beds has defcended to 60 or 70 degrees, 

 (centigrade) at which period, water of the fame heat is poured 

 into the mattrafes. The water dilutes the refidue of the dif- 

 tillation, which mixture is to be poured out, and the veflels 

 fuftered to cool in balkets containing ftraw. Jf the precau- 

 tion of introducing hot water in this manner upon the refidue 

 were not taken, it would become fo folid when the operation 

 is performed with fulphuric acid, in the manner we are about 

 to defcribe, that it could not be extracted without much 

 trouble and danger of breaking the veflels. 



If the difengagement of the gas be made bv fulphuric acid, Procefs with 

 the following dofes are ufed : ' < u, P huric acid * 



Oxide of manganefe - - - - 25 kilograms 

 Muriate of foda - - - - - 70 



Sulphuric acid at 50 degrees of denfity 25 



Total 120 



The acid is to be diluted with an equal bulk of water, or 

 16 litres, which will reduce its denfity to 31 degrees. 



The eighth part of this for each mattrafs amounts to 1 4| 

 kilograms. 



The oxide of manganefe and muriate of foda being pulve- 

 rized are mixed together. The mattrafs is to be charged and 

 the operation conducted as before defcribed. This method is 

 the molt economical, becaufe the fulphuric acid is cheaper 

 than the muriatic, and alfo becaufe it is practicable to obtain 

 from the refidue of the diftillation, the foda of the muriate 

 which is converted into Tulphate of foda ; that fait being de- 

 compofable by well known proeefles. 



In order to meafure the force of thefe liquors, or their To a f certa ; n t <^ & 

 1 leaching power, we made ufe of the folution of indigo pre- ftrengthof the 

 fcribed by Citizen Def roizilles, which is prepared in the ble <" hin 6 H*" 

 following manner : 



In a glafs mattrafs put of concentrated fulphuric acid at 66 By j^igo, 

 decrees of denfity, feven parts by weight, and of pulverized 

 indigo one part; agitate the mixture, and plunge the ball of 



flic 



