Pfocefs for Bleaching R,iw SiJL •> -, 



kept for a certain time in a mafs to preferve their heat, and cffl-£lually deftroy fuch of the 

 infe£ls as might have efcaped the power of the oven. The efFecfl of this procefs is, that the 

 fiiic is hardened, and is more difficult to wind off than before. Hence the product of filk 

 is lefs by one ninth part in quantity, and inferior in quality to what might have been ob- 

 tained by winding off without this previous baking. Mr. Baume, not only from thefe 

 views, but llkewife becaufe the filk which has not been baked proves fufceptible of a 

 greater luftre, was induc.^d to deftroy the chryfalis by fpirit of wine. For this purpofe he 

 difpofes them in a wooden box in a ftratum fix inches deep : upon each fquarfi foot half a 

 chopin, or fomewhat more, of fpirit of wir.^ is to be fprinkled with a fmall watering-pot 

 made for that purpofe. This quantity anfwers fufficiently near to our half-pint. The 

 liquid is to be equally diftributed, but it is not neceffary that all the cocons fliould be wetted. 

 They are then to be mixed by hand. In the next place another flratum is to be formed over 

 the firft, nearly of the fame depth, ~vi'hich is to be fprinkled and treated as before. By 

 this method of proceeding, the box becomes filled, and muft then be covered, and left for 

 twenty-four hours, during which time they become fpontaneoufly heated to about loo 

 degrees, and the vapour of the fpirit of wine exerts itfelf with wonderful aflivitv. Five 

 hundred French pounds * of the cocons require ten French pints, which is nearly the fame 

 number of Englifh quarts. After this treatment they muft be fpread out to dry, which 

 happens in a fhort time, and is abfolutely neceffary previous to winding off. 



When the operator propofes in this manner to extinguifli various parcels of cocons be- 

 longing to different individuals, each parcel may be tied up loofely in a canvas bag, and 

 wetted on the outfide previous to clofmg the box. 



The fpirit of wine to be ufed in this operation, ought to be of the ftrength of 34 degrees 

 of Baume's hydrometer at the temperature of 55 degrees. It is of the greateft importance 

 to ufe that fpirit only which has been kept in veffels of glafs, of tinned copper, or of pure 

 tin. Leaden veffels are abfolutely to be rejeifted ; wooden veffels tinge the fpirit, which 

 gives the filk a degree of colour of confiderable folidity, and very inimical to the bleaching 

 procefs. 



With regard to the advantages of this method of extinclion, in-preference to that of the 

 oven, the author remarks, that the coft of labour and fuel added to the lofs of filk, and the 

 probability of injury from too much or too little heat, conftitute a fum of difadvantao-e 

 much greater than the coft of the fpirit of wine. It is befides a confiderable advanta"-e 

 that the fpirit of wine renders more diftinguifhable fuch cocons as have periflicd previous 

 to the application of the fpirit. Thefe afford a much worfe filk, and muft be picked out. 



The filk is wound off upon a reel, while the cocons are kept immerfed in water almoft 

 boiling. Upon this part of the procefs Mr. Baume remarks, ift. That the dead cocons 

 muft be fcparated. Thefe are known by the brown or black fpots on their furface. 

 2. That well-water, which on account of its clearncfs is almoft univcrfally ufcd in the filk 

 manufaclories, moftly contains nitre, and is extremely prejudicial to the bleaching pro- 

 cefs. The prcfenee of nitrous acid gives a yellow colour, which refifts bleaching and even 

 fcouring ; he therefore recommends river-water. 3. In fome countries a fmall quantity of 



• The Paris pound h to ilic Englilh avoirdupois pound as 756 to 700. I have not reduced thefe quantities 

 bccaufc cht opcr,iiion requires no great precifion. N. 



Vol. I.— April 1797. F • aluni 



