27 & On the Effect of Mordants, izfc. ' 



and becomes grey •, the bath prefents no precipitate, becaufir 

 the operation takes place in the tiflue of the cloth itfelf, 

 where the production remains fixed. It is however to be 

 obferved, that if the galled cotton be pafied through a too- 

 warm folution of alum, a portion of the galls efcapes from 

 the tiffue of the ftuff, and the decompofition of the alum 

 takes place in the bath itfelf ; which diminifhes the propor- 

 tion of the mordant, and impoverifhes the colour. 



We have here therefore a combination of three principle's 

 (oil, the aftringent principle, and alumine) which ferve as a 

 mordant for the red dye of madder. Each of them employed 

 feparatily produces neither the fame fixation nor the fame 

 lufire in the colour. 



This mordant, without difpute, is the moft complex knowiv 

 in dyeing, and it prefents to chemiftry a fort of combination 

 which it is of the utmofi: importance to iludy. It is from 

 the precifion in this combination, and the judgement fhewn 

 by the artift himfelf to. produce it, that a beautiful colour 

 can be ex peeled ; but if it be pofiVolc for him to conduct 

 himfelf through the labyrinth of thefe numerous operations, 

 by taking the clue of experiment as his guide, it will at any 

 rate be very difficult for him to Amplify hisprogrefs, or bring 

 it to perfection. It is only by reafoning on his operations, and 

 calculating the refult and principle of each, that he can hope 

 to become matter of his procefTes, to correct their faults, 

 and to obtain invariable products. Without this, the 

 practice of the moll experienced artift will afford nothing in 

 his hands but the difcouraging alternative of fuccefs and dif- 

 appoihtment. iVifhed therefore in this fliort analyfis of 

 the procefs for dyeing red, which is the moft complicated 

 of all, to gjve an in fiance of what chemiftry can do in the 

 arts when its principles are properly applied. I will venture 

 to affert, that the moft uninformed workman will here find' 

 the principle of bisart and the rule of his conduct. 



IX. On 



