64 ON THE ADULTERATION OF COCHINEAL. 
solutions obtained, as described above, are taken ; some of 
these solutions are introduced into the colorimetric tubes as 
far as zero of the scale, which is equivalent to 100 parts of 
the superior scale ; these tubes are placed in the box, and 
the tint of the liquids enclosed is compared by looking at 
the two tubes through the eye-hole, the box being placed 
so that the light falls exactly on the extremity where the 
tubes are. If a difference of tint is observed between the 
two liquors, water is added to the darkest (which is always 
that of the cochineal taken as type) until the tubes appear 
of the same tint.* The number of parts of liquor which 
are contained in the tube to which water has been added is 
then read off; this number, compared with the volume of 
the liquor contained in the other tube, a volume which has 
not been changed, and is equal to 100, indicates the relation 
between the coloring power and the relative quality of the 
two cochineals. And if, for example, 60 parts of water 
must be added to the liquor of the good cochineal to bring 
it to the same tint as the other, the relation of volume of 
the liquids contained in the tubes will be in this case as 160 
is to 100, and the relative quality of the cochineals will be 
represented by the same relation, since the quality of the 
samples tried is in proportion to their coloring power. 
Conclusion. 
1. The adulteration of cochineal by a metallic substance 
mentioned by M. Boutigny, is not of frequent occurrence 
in the trade, but it exists. 
2. The value of the different cochineals tried may be 
separated into very distinct classes. The rosette cochineal 
and the gray cochineal, which I have always taken for 
comparison, appear to me to be the richest met with in the 
* For diluting the liquors the same water must always be used which 
has served to extract the coloring matter of the cochineals under exami- 
nation, otherwise the darkest decoction would pass into violet as water 
was added to it to bring back the tint to the same degree of intensity as 
that of the decoction to which it is compared. 
