ON MADDER. 
129 
ture. After this it is made to boil for half an hour, the sam- 
ples are taken oat, rinsed in cold water and dried. Each 
dyed piece is cut in half; one-half is preserved as it is, the 
other is subjected to the following clearings: — We begin 
by a soap-bath at 122°, made wiih 8| grms. of white soap 
to each litre of water. After it has been half an hour in 
this bath, the cloth is carefully rinsed in cold water. A 
fresh soap-bath is given, to which is added half a gramme 
of salt of tin, and which is kept at boiling point for half an 
hour. It is washed and rinsed. The well-rinsed samples 
are dried with care and preserved from the light. 
When a series of tints of two different states have been 
thus prepared, that is to say, a dye without and with clear- 
ing, it is very easy to ascertain the comparative value of 
an unknown madder. In fact it is sufficient to take 10 grms- 
from the barrels, and to go through the preceding opera- 
tions on 5 square centimetres of suitably-mordanted calico, 
and to compare the dye obtained, before and after the clear- 
ing, with the ten samples. If, for example, the shade is equi- 
valent to No. 5 of the madder, it may be concluded that the 
unknown madder is inferior by half to the madder-type, 
since 10 :5 : : 100 : x = 50. 
Whatever vegetable powders may have been fraudulent- 
ly introduced into the madders, whether tinctorial or inert, 
they can never lead to error as to the true tinctorial value ot 
the mixture, inasmuch as the colors which they afford, and 
which saturate the mordants at the same time as the red 
principle of the madder, cannot withstand the action of the 
clearings as the latter does; they run,&s is said, in the soap 
and tin-baths, and in the end there only remains the color 
from the madder upon the tissue. The clearings are there- 
fore necessary to show the solidity and vivacity of the tints 
obtained. 
Instead of printed calicoes, skeins of oiled and mordanted 
cotton may be used in the state in which they are prepared 
for dyeing Turkey-red. In this case skeins of the weight of 
vol. x. — NO. II. 12 
