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ON MADDER. 
There are two kinds of adulterations. Sometimes earthy 
or mineral substances are incorporated with the powder of 
madder ; sometimes vegetable substances are added to it, 
the coloi of which resembles that of madder. 
1. Adulteration by Mineral Substances. — The mineral 
substances which have been introduced, or which are still 
found in ground madders, are brick-dust, red and yellow 
ochre, yellowish sand, yellowish clay or argillaceous earth. 
A madder which contains earthy substances grates between 
the teeth when chewed. 
A small quantity of such a madder, for example from 25 
to 30 grms., introduced into a large glass globe and diluted 
with 5 or 6 litres of water, quickly deposits the greater por- 
tion of the earthy substances at the bottom of the vessel. 
When the suspended matter is decanted, and the deposit 
agitated with a fresh quantity of water, the earthy sub- 
stances are isolated and may be examined. 
However, to determine the proportion, more exact pro- 
cesses must be had recourse to* The best is that of calcin- 
ing, at a red heat, in a platinum crucible. 
5 grms. of the madder under examination are first dried 
completely at 212° Fahr., and are weighed with great ex- 
actness, and then put into the platinum crucible, which 
must be weighed beforehand. The crucible is shut and 
heat gradually applied. When perfectly incinerated, the 
crucible is taken out of the furnace and left to cool, and 
then weighed. Its weight being deducted from the quan- 
tity employed, the difference gives the proportion of cinders 
obtained. 
These cinders are composed — 1st, of the fixed mineral 
matters contained in the root; and 2d, of the earthy sub- 
stances, foreign to the chemical constitution of the root, and 
which have been accidentally or fraudulently mixed with 
the madder. 
Some experiments which I made with M. Labillardiere 
on a large scale, in 1828, showed us that madder which is 
