2^ Priccfs for Bleaching Raw Sili. 



alum is ufcd. Neither this nor any other faliiie fubdance is of the leatl advantage to the- 



colour, bt.iuty, or quality of the Clk. 



At the four places of contacl of the filk upon the reel, all the threads (lick together. It 

 is abfolutely iieceflary that this fliould be remedied. Tlie method confiflsin foaking tlie filk 

 in a fuQicient quantity of warm water, at about 90 degrees, for about two hours; after which 

 the threads are to be fcparated by opening tlie hanks upon a pin, and lightly rubbing the 

 parts which cohere. ^Vhen the filk is dry, it is to be loofcly folded in its original form, and 

 is ready for bleaciiing. 



The filk while wet is foft, and part of its gummy matter is in fuch a ftate, that its 

 threads would readily adhere, if wrung while warm for the purpofe of clearing it of the 

 water. After fuch improper treatment there would be no other remedy than to foak it 

 again in warm water. 



The apparatus for bleaching the filk confills of a ftone-ware vefTcl, nearly of a conical form,, 

 capable of holding about twelve gallons, having a large opening at the one end, and a fmallcr 

 of about an inch diameter at the otlier end. Common pottery cannot be ufcd in this opera- 

 tion, becaufe it is foon rendered unferviceable by the aclion of the marine acid, and the 

 flone-ware itfelf is not very durable. This veffel muft be carefully examined, to afcertain- 

 that it does not leak in the flighted degree -, after which the infide is to be rubbed with a 

 pumice-flone, to clear it of afperities which might break the tlaeads. A cover of the 

 fame material is to be fitted on by grinding ; and the fmaller aperture, which in the ufe is 

 the loweft, is to be clofcd with a good cork, in the middle of which is thruft a fmall glafs 

 tube about a quarter of an inch in diameter ; this is likewife (lopped with a cork, except- - 

 ing at the time when it is required to draw off the liquid contents of the jar. A fmall per- 

 forated falfe bottom is placed within the velTel, to prevent this tube from being ob(lru£led. 

 This jar, or as many of them as the purpofes of the manufactory may require, is fup- 

 ported by a wooden frame or table, at fuch a height that a calk may be conveniently placed 

 beneath to receive what may flow from the glafs tube in the fevcral periods of the operation. 

 Six pounds of yellow raw filk are to be difpofed in the earthen pot ; upon this is to be 

 poured a mixture, previouQy made, of forty-eight pounds* of fpirit of wine at 30 degrees, 

 with twelve ounces of very pure marine acid, abfolutely exempt from all prefence of nitrous 

 acid, and of the (Irength of 14 or 15 degrees of Baumi's hydrometer. The pot is then to 

 be covered, and the wliole left in digeftion till the following day, or until the liquor, which 

 at firll alTumes a (inc green colour, fliall begin to alTume tliat of a duflcy brown (feuiHe morte). 

 The acidulated fpirit is then to be drawn off. To prevent evaporation, M. Baume 

 thrufts a cork in the bung-hole of the receiving ca(k, in which is a Aiding glafs tube. The 

 ufe of this tube is completely to furround the fmall tube proceeding from the earthen 

 TclTel. When the whole of the fluid is thus almoft entirely drawn o(F, clean fpirit of wine 

 is poured upon the filk, and drawn off repeatedly until it palTes colourlefs. The filk is then 

 fufTcred to drain without ftirring it. In this ftate 1!. is ready for a fecond infufion. 



Forty-eight pounds of fpirit of wine acidulated with twelve ounces of marine acid is 

 now to be poured on the filk, and the whole fuffered to remain for twenty-four hours or 

 longer, until the filk becomes perfedlly white. The time required for this fecond infufion 



• The pound is nearly a pint, and is divided into Cxtccn ounces. With regard t« the fircngihs, fee 

 Article IX. p. 37. 



