S8 Prc.-.fifor Bleachiiig Raw Silh. 



ihc large furfacc cxpofcd to fridion, I conclude, that the machine defcribcd in this paper is 

 at kail equal in Heady intenfity, and much fuperior in power of charging, to any cylinder- 

 machine which has ever been made. 



VIII. 



77v Proccfs/or ^ivi't^ a Icjut'iful ]VhUe Colour to Raw Silk nvithjiit Scouring. By M. BaVME *. 



[Concluded from page 32.] 

 1 O complete the defcviption of M. Baume's procefs for bleaching filk, nothing more re- 

 main?, than to fliew in what manner he recovers the ardent fpirit, and cnfures the purity of 

 the acids made ufe of. Thefe circumdanccs arc of efTential importance to the art: for the 

 procefs would be much too expcnfive if the fpirit «cre loft, and it couM not be made to 

 fucceed at all if the acid were impure. 



Tlie aJcohol which has been uicd in bleaching filk, is acid, and loaded with colouring 

 matter. In this ftate it cannot be again ufed. There are two methods of diflilling it ; 

 which have their refpeclive advantages and inconveniences. By the firft, the acid is loft ; 

 which is fatur.ited with pot-afli, ift order that the diftillation may be afterwards performed in 

 a copper alembic. The feeond is performed by diftilling with glafs retorts, or an alembic 

 of filver. In either of thefe vefTels, which are not aiSled upon by the marine acid, the diftil- 

 lation may be performed, and the greater part of the acid recovered^ 'I he inventor moft 

 generally praftifed the fatur.nion of the acid from rcafons of convenience ; but recom- 

 mends the ufe of a Tilver alembic, as being moft economical upon the whole, in a manu- 

 faflory. 



A folution of pot-afli is to be poured into the acid fpirit and ftirred about to promote 

 thefaturation. Carbonic acid is difengaged with ftrong cifervefcence from the alkali, and 

 the point of faturation is known by the ufual teft, that the fluid does not redJen the tincture 

 of turnfol. The diftillation is then to be made in the copper alembic, and the alcohol re- 

 ferved in proper veffcls, as mentioned at the beginning of this Memoir. 



If too much alkali fliould h.ive been added, the liquor remaining in the alembic may be 

 ufed in another faturation. The alkali in this procefs being an expenfive article, Mr. Baumc 

 endeavoured to fupply its place by chalk, quick-lime, and lime which had been flaked by 

 ■expofurc to the air. But he found that the adlion of the fpirit upon the calcareous earth, 

 or perhaps the abfence of water, prevented the acid from uniting with that fubftanee. The 

 union does not take place to perfeft faturation in lefs than five or fix weeks, even when the 

 alcohol is diluted with upwards of fifty times its bulk of water. 



In the feeond procefs for diftilling without alkali, the acid fpirit is diftributed into a great 

 number of glafs retorts, placed in the fand-bath, on the gallery of a furnace. The firft 

 producl isfcarccly acid ; but v.-liat follows is more and more fo, and muft be kept in vefl'cls 

 of glafs or ftone ware, whith become embarrafting on account of their number. The fluid 

 •which remains in the retorts has the colour of beer flightly turbid, and contains the greateft 

 part of the marine acid. It muft be poured into one or more retorts, and concentrated by 



* The Editors of the Journal Ac rhyfi<]uc, to which reference was made at the beginning of this Abflraft, 

 omitted to mention how tliey obiaine J it. 1 find in the Annalcs dc Chimii., XVII. 156, that it was read at the 

 Public Meeting of the Academy at Paris, April 10, 1 793. 



' . heat 



