62 ON THE ADULTERATION OP COCHINEAL. 
mentioned, in addition the gray cochineal No. 2, which is 
frequently met with, and a cochineal which is quite black 
and contains a little sand. It is almost always in these 
last two that I found matters introduced to increase the 
weight. 
When examined with a glass, the metallic powder that I 
obtained from four specimens only of cochineal out of 
twenty-three, presented all the physical characters of lead 
filings. Treated with nitric acid, it yielded a solution, 
which, when tested with chemical agents, showed all the 
characters peculiar to the salts of this metal. 
The result from what precedes is, that the adulteration 
mentioned by M. Boutigny is but little spread in the whole- 
sale trade; that this sophistication is, as I suspected, made 
in France and with the exhausted cochineals. 
Color imetric Tests. — I shall not describe the colorimeter, 
but shall refer for that to the memoir of M. Houton Labil- 
lardiere, in the < Bulletins de l'Academie Royale,' 1827, p. 
73. The memoir of M. Girardin, inserted in the £ Bulletin 
de la Societe Libre d'Emulation,' 1836, p. 149, may be 
consulted. 
The coloring matter of cochineal being soluble in water 
I have used this solvent for exhausting the different kinds 
which I have submitted to examination in the colorime- 
ter. I operated in the following manner : — I took a grain 
of each of the cochineals to be tried, dried at 122° F. ; I 
submitted them five consecutive times to the action of 200 
grains of distilled water at water-bath heat, each time for 
an hour ; for every 2 00 grains of distilled water I added 
two drops of a concentrated solution of acid sulphate of 
alumina and of potash. This addition is necessary to ob- 
tain the decoctions of the different cochineals exactly of the 
same tint in order to be able to compare the intensity of the 
tints in the colorimeter. 41 
* Care must be taken not to add to the water, which serves to extract the 
coloring matter from the different cochineals, more than the requisite quan- 
tity of acid sulphate of alumina and solution of potash, because a stronger 
dose would precipitate a part of the coloring matter in the state of lake. 
