ISO 
ON MADDER. 
10 grms. are taken and dyed with different weights of good 
madder, from 20 to 30 grms., in order to obtain a scale of 
ten distinct shades. 
This test is that which I have employed since 1831, and 
which has been since adopted in all our print-works of Rouen 
and Bolbec, where my pupils have introduced it. It differs 
very little from that which was published in 1835 by M. H. 
Schlumberger of Mulhausen. 
3. Determination of the Quantity of the coloring Prin- 
ciple. — The most exact process hitherto published is with- 
out doubt that made known by M. H. Schlumberger in 
1838, as modified by M. Scheurer. But this process, which 
is founded on the solubility of the red coloring principle of 
the madder in weak acetic acid, a fact pointed out as early 
as 1829 by an anonymous chemist, is unfortunately too sen- 
sitive, and requires too great a degree of skill in the ma- 
nipulation to become general. 
The following is the method which I have long been ac- 
customed to employ : — 50 grms. of madder are diluted with 
50 grms. of concentrated sulphuric acid. The whole is left 
in contact for some hours ; too high a temperature should be 
avoided ; the charcoal obtained is mixed with water and 
thrown upon a filter; it is then washed until the water 
passes through quite insipid; and next dried at a tempera- 
ture of 212° Fahr. in Gay-Lussac's water-bath. This char- 
coal is reduced to a fine powder and macerated for two 
hours at three distinct intervals with cold alcohol containing 
a little ether, in order to free it from a fatty matter which 
it retains. The powder is boiled in alcohol of 0.834, at 
three different intervals, employing each time about 250 
grms. of alcohol. When this is no longer colored by ebul- 
lition, the alcoholic liquors are mixed, and distilled in a 
small glass retort to the consistence of a syrup, and the con- 
centration of the liquid completed in the water-bath in a 
weighed porcelain crucible. When the extract is perfectly 
