360 Mr, Henry's Confiderations on different Materialst 



luftre, are faid to be prepared without foap. The 

 French Academy, therefore, fome years ago, 

 offered a prize for the difcovery of a method of 

 cleaning filk, without foap; and the prize was 

 obtained by M. Rigaut, whofe mode was to ufe 

 a flender alkaline folution inftead of foap. 



But Monf. I'Abbe Cullomb* has lately gone 

 farther, and has aftually difiblved in water, the 

 varnifh of filk, which has always been fuppofed 

 to be of that oleo-refinous kind, as not to be 

 afted on even by fpirit of wine. He expofed a 

 quantity of raw filk to the adion of boiling -^|pp 

 water, for nine hours, and found it freed from the 

 varnifh, with the lofs of one fourth of its weight. 



Though the filk, by thefe means, acquires a 

 confiderable degree of whitenefs ; if intended to 

 receive fome of the moft brilliant colours, a far- 

 ther operation is requifite. This confifts in ex- 

 pofing the filk to the fumes of burning fulphur, 

 fo confined in a ftove, that none ihall efcape, 

 but the whole be applied to the material in- 

 tended to be whitened. Of the rationale of this 

 operation Mr. Delaval has given a very ingenious 

 explanation, j- 



But, though thus rendered more fit for exhi-t 

 biting the brilliant colours, the attradtion of the 

 filk, for colouring matter is rather diminilhed 



♦ Journal de Phyfique, part II. vol. XXIX. 

 f Maachefter Memoirs, vol. II. p. z. 



than 



