58 
ON THE ADULTERATION OF COCHINEAL. 
its immersion in boiling water at the time of gathering. 
He is not of the opinion of Boutron Charlard, who thinks 
that both are equal in quality. The latter person says, 
contrary to Guibourt, that black cochineal is transformed 
into gray, because this last is of more value. 
The result of all these contrary opinions is, that it is per- 
fectly impossible to judge of the goodness of a cochineal 
by its physical characters. In order to ascertain its value, 
we must have recourse to comparative experiments. We 
are indebted to MM. Robiquet and Anthon for two methods 
of determining the quality of cochineals according to the 
quantity of carmine they contain. The process of M. 
Robiquet consists in decolorizing equal volumes of decoc- 
tion of different cochineals, by chlorine. Using a gradu- 
ated tube, the quality of the cochineal is judged of by the 
quantity of chlorine employed for decolorizing the decoc- 
tion. The process of M. Anthon is founded on the pro- 
perty which the hydrate of alumina possesses, of precipi- 
tating the carmine from the decoction so as to decolorize it 
entirely. The first process, which is very good in the 
hands of a skilful chemist, does not appear to me to be a 
convenient method for the consumer ; in the first place, it 
is difficult to procure perfectly identical solutions ; in the 
next place, it is impossible to keep them a long time with- 
out alteration. We know that chlorine dissolved in water 
reacts, even in diffused light, on this liquid, decomposes it, 
appropriates its elements, and gives rise to some compounds 
which possess an action quite different from that of the 
chlorine solution in its primitive state. The second process 
seems to me to be preferable, as the proof liquor may 
be kept a long while without alteration. A graduated tube 
is also used; each division represents one hundreth of the 
coloring matter. Thus, the quantity of proof liquor added 
exactly represents the quantity in hundredths of coloring 
matter contained in the decoction of cochineal which has 
been submitted to examination. 
