443 
and Dyeing Turkey Red. 
time of a small portion of the colouring parts of the mad- 
der, which cannot he entirely exhausted except by then 
increasing the heat to ebullition : but as the colours thus 
obtained are degraded more or less in the ratio of the 
quantity of the madder, the gall-nut or shumac used, this 
method must be employed with caution, and principally 
for common effects, either in regard to cotton or linen* 
To avoid as much as possible the loss of madder after 
the mad de ring of good articles has been terminated, and 
before the common ones are put into the boiler, powder- 
ed gall-nut or shumac must be added, with a new, but 
small portion of madder : the process must be managed 
also in such a manner, that the ebullition shall not take 
place till two hours after. 
I several times tried to exhaust the madder by simple 
ebullition, and without adding any thing else than chalk; 
but I found that this was unfavourable to all colours, 
black excepted : it even appeared that the effect of the 
madder was much less than when the heat was mode- 
rately applied, and when the accumulated caloric easily 
decomposed the colouring substance. It is this tenden- 
cy to be decomposed, and particularly by fermentation, 
however little it he moistened or diluted with water, 
which has hitherto prevented me from obtaining a sub- 
stantial colour, pretty dark, and sufficiently fixed to be 
applied on any kind of stuff. I observed also, that if 
the heat was carried too far the first time, in circum- 
stances when it was proposed to madder a second and 
third time, it prevented me not only from obtaining 
bright and agreeable shades, but also of the requisite in- 
tensity. The aqueous vehicle of the madder, at too high 
a temperature, never fails to weaken the adhesive force 
of the alumine and the oxide of iron to the stuff, and to 
take from it a portion, which an experienced eye may ea- 
sily remark on examining the bath. 
