as Ohje5fs. of the Art ofDymg, i^c. 407 



cotton J and even folutions of that metal, made 

 by macerating it with alder bark and water, in 

 which the aftringent principle fhould feem to 

 unite with the vegetable acid, to form the folvent. 

 In thefe folutions the iron is not too much depri- 

 ved of its phlogifton ; and contrary to thofe made 

 in mineral acids, they improve with age, for the 

 vegetable acid, tending to putridity evolves phlo- 

 gifton, which unites with the iron; whereas the 

 vitriolic Iblution is continually parting with that 

 volatile principle, and thereby becoming not 

 only lefs fit for producing blacknefs, but the calx 

 of iron, when highly dephlogifticated, is very 

 injurious to the texture of the cloth. 



The improvements made in the dying black, 

 are perhaps the ftrongeft proofs that can be 

 given of the utility of chemical knowledge. 

 Nor can a more apt inftance be adduced of the. 

 inconvenience arifing from the want of it, than 

 the French procefs, related by M. Macquer 

 for this purpofej in which no lefs than thirty 

 different ingredients, or at leaft bearing different 

 names, are direded to be employed ; feveral 

 of which are the fame things under different 

 denominations ; and others tend direftly to de- 

 ftroy each other. 



I know not whether to apologife more to the 



Society, for the length of this paper, or for the 



'mperfedions it contains. The former I could 



D d 4 not 



