as OhjeSls of the Art ofDyingy (^c. 379 



this purpofe, on cotton ; but that acid being re- 

 quifite for the produ(5lion of this beautiful colour, 

 and being highly corrofive to cotton, this bafis 

 is prevented from being applied to that fubftance. 

 But if this metallic earth has any preference to 

 alum, for other colours on cotton ; it might be 

 procured united to acetous acid, by a procefs, 

 which I have lately difcovered, fomewhat fimilar 

 to that for making the printer's liquor j viz. by 

 adding to a folution of tin in marine acid, a fo- 

 lution of fugar of lead. The marine acid will 

 unite with the lead, and precipitate as plumbum 

 £orneum ; and the vegetable acid will unite with 

 tiie tin — with which it could not eafily be fatu- 

 rated by any other mode ; for the acetous acid 

 has very little power to diflblve tin in its metallic 

 form. 



The cupreous bafis may be obtained from blue 

 vitriol, and from verdigreafc, or acetated cop- 

 per. It is feldom ufed by itfelf, but generally 

 in conjunftion with alum. 



The martial bafis, where wool and filk is con- 

 cerned, is obtained from green vitriol or cop- 

 peras ; but, this bafis is beft procured for cotton, 



Q'Q. 



from a folution of icj^n acetous acid, or even as it 

 (hould feem in the aftringent principle. For a fo- 

 lution of iron is ufed by the dyers of cotton with 

 great fuccefs, which is formed by ftratifying old 

 iron with alder bark, and digefting them in 

 water. 



It 



