haps, he alludes, Epit, 
in dyeing Cotton. sy 
- Itis by fuch or almoft fimilar proceffes that dyers com- 
wunicate, what is called among workmen, an ochre or ruff 
colour. But thefe colours are attended with feveral. incon- 
veniences to the artift. 1. Strong fhades burn or injure 
the cloth. 2. This colour is harfh, difagreeable to the eye, 
and cannot be eafily united with the mild colours furnifhed » 
by vegetables. I made attempts therefore to avoid thefe in- 
conveniences, and fucceeded in the following manner: I: 
tread the cotton cold ina folution of the fulphat of iron, 
marking three degrees, wring it carefully, and immediately 
plunge it in a ley of potafh at two degrees, upon which I 
-have poured to faturation a folution of the fulphat of alu- 
mine: the colour is then brightened, and becomes infinitely 
more delicate, foft, and agreeable. The fulphat no longer 
attacks the tiffue of the ftuff; and after the cotton has been 
left in the bath for four or five hours, it is taken out to be 
wrung, wafhen and dried, In this manner we may obtain 
every fhade that can be wifhed, by graduating the ftrength of 
the folutions, This fimple procefs, the theory of which 
prefents itfelf to the mind of every chemift, has the advan- 
tage of furnifhing a colour very agreeable, exceedingly fixed, 
and, above all, extremely economical. I employ it with great 
advantage in dying nankins, the colour of which has infi- 
nitely more fixity than that of the Englifh (dyed) nankins*, 
Tt poffefies over the latter the advantage of refifting leys ; 
and the only fault I have difcovered in it is, that it becomes 
brown by the aétion of aftringents. 
I thought for fome time that it would be poffible to com- 
bine this yellow with the blue of indigo, to obtain a durable 
green: but hitherto I have been deceived in my hopes ; and 
jt refults from different trials which I made on this fubject, 
that there is not a fufficient affinity between the blue of 
* Was the author aware that the Englifh nankins are made from a cot- 
ton wool of the natural colour that requires no dyeing procefs? Some 
jeans and other ftuffs are dyed by means of oxyd of iron: to thefe, per- 
indi go 
