378 Mr. Henry's Conftderations on different Materials, 



fuperabundant acid ; and would perhaps be 

 better made to the alum, before the mixture of 

 the fugar of lead. For as that acid immediately 

 precipitates fome of the lead, without furnifhing 

 the acetous acid with aluminous earth in return, 

 a wafte of the Jaccharum Jaturni is the confe- 

 quence, which might be prevented by the mode 

 now recommended. 



The folutions of tin, and the other white metals, 

 fhould be as perfeftly faturated as poflfible j 

 otherwife not only the fuperabundant acid will 

 injure the cloth, but the calx will not fo readily 

 precipitate, to form the white bafis. In the dy- 

 ing of wool, the folution of tin is mixed with the 

 decoftion of cochineal, and falls in the form of 

 carmine on the cloth. But filk. has in vain been 

 attempted to be dyed fcarlet, in this mode. M. 

 Macquer has however accomplifhed this de- 

 fideratum, by firft fully impregnating the filk. 

 withthe folution, before he proceeded to the dying. 

 By this means M. Macquer declares that he has 

 produced fcarlet, though not equal to that dyed 

 on wool ; yet fufRciently beautiful, and fuperior 

 to the fcarlet formed by a mixture of fafflowcr 

 and arnatto. And, he adds, that an eminent ma- 

 nufaflurer at Lyons had fucceeded in dying great 

 variety of colours on filk, by applying the tin 

 bafis, after the fame manner*. 



If a fcarlet could be dyed without the ufe of 

 nitrous acid, the tin bafis might be employed for 

 * Diftionaire de Chymie, 2d Edit, 



this 



