An EJ/ajf on Bleaching. 1 05 



when the (ilk is dry, it is then fulphured, and the bleaching 

 is complete. 



All thefe proceffes are exceedingly deftructive : thofe which 

 I am about to propofe will make a total change in the me- 

 thod of bleaching (ilk. I have already mentioned the prize 

 granted by the Academy to Rigaud for fcouring by means 

 of a (lightly alkaline ley, and the fuccefs obtained by the 

 abbe" Colomb in having fucceeded to diffolve the varni(h of 

 lilk by the action of boiling water at a very high tempera- 

 ture : thefe inconteftable facts furnifh more than the necef- 

 fary proofs of the goodnefs of our method. 



Take a folution of cauftic foda, fo weak as to mark only a 

 fourth of a degree at molt of the areometer for falts, and till 

 with it the boiler of the apparatus for bleaching with fteam. 

 Charge the frames with fkains of raw lilk, and place them in 

 the apparatus until it is full ; then clofe the door, and make 

 the folution boil. Having continued the ebullition for twelve 

 hours, flacken the tire, and open the door of the apparatus. 

 The heat of the tteam, which is always above 250 degrees, 

 will have been fufficient to free the (ilk from the gum and to 

 fcour it. Wafli the fkains in warm water, and, having 

 wrung them, place them again on the frames in the appa- 

 ratus, to undergo a fecond boiling. Then wafh them feveral 

 times in water, and immerfe them in water fomewhat foapy 

 to give them a little foftnefs. 



The laft degree of bleaching is effected by making the 

 (kains to pafs through fulphurous acid, making ufe of the 

 procefs and apparatus before recommended for bleaching 

 wool, and which fupplies here the place of fulphuring. The 

 incalculable advantage of this procefs in companion of any 

 other, confifts chiefly in the poffibility of following its opera- 

 tions progreffively, and without running the rifk of injuring 

 the quality of the lilk by too violent leys. 



Of the Bleaching of Vegetable Matters, 



The characters and properties of vegetable fubftances are 

 widely different from thole we have defcribed. As organic 

 matters, they contain oxygen, hydrogen, and carbon ; but 

 azote, which acts fo important a part in the animal king- 

 dom, is rarely found in them, and much lets phofphorus and 

 fulphur. 



The fub fiances found in theinterior of plants are, like thofe 

 obferved in the interior of organized bodies, the refult of ve- 

 getable fecretion. The nounihment of vegetables is derived 

 trom the boforo of the earth, and this combination of prin- 

 ciples 



