ON THE ADULTERATION OF COCHINEAL. 59 
In my investigation I have not had recourse to chemical 
agents as did MM. Robiquet and Anthon; I had no hope 
of finding a better and more simple process than those pro- 
posed by them. I employ nearly the same course for co- 
chineal as that followed by M. Girardin for annotto. In a 
word, it is by colorimetric essays that I judge of the quality 
of the cochineals of commerce. This method appears to 
me so simple and so convenient, that 1 think it right to 
make it known. It enables the consumer to judge of the 
value of a cochineal as well as the chemist. 
As I have before said, two kinds of cochineal are found 
in commerce, gray and black. The gray cochineal may be 
separated into two very distinct varieties. The first is 
large, heavy, regular ; the eleven rings which form it are 
distinctly seen. The insect has pretty nearly preserved its 
form, convex on one side, and concave on the other; its 
gray color is owing to the whitish powder with which it is 
covered during its growth. The second variety is irregular 
and quite without form. The whitish coating which covers 
it is heaped in such great quantities in the concave part and 
between the rings of the insect, that it is in the form of 
small round masses, in which it is hard to distinguish any 
traces of the rings so well characterized in the first variety. 
This cochineal is in general the heaviest : it almost always 
contains, independent of the talc in which it has been rolled, 
some sand or metallic dust, which singularly increases its 
weight. 
Black cochineal does not offer very distinct characteris- 
tics ; it is sometimes like the gray cochineal, No. 1, heavy, 
concave on one side, convex on the other ; at other times it 
is quite irregular, small and wrinkled in every direction; it 
is almost impossible to distinguish its first form and some 
traces of the rings which compose it. These latter charac- 
ters belong especially to zacatillee cochineal. 
Exhausted Black Cochineal. — Until 1840 the calico- 
printers, after having treated the cochineal at different in- 
