171 
details, especially in the precautions taken to avoid overheating 
the cochineal, and above all in the addition of whitening, with- 
out which it would fail entirely. 
I will now detail a few experiments which I think will throw 
a good deal of light on the theory of carmine making; and 
establish the fact of the existence of at least two distinct colour- 
ing principles in cochineal. 
(1) Ifno whitening be added to the cochineal, nothing but 
a small quantity of a dirty purplish, precipitate is obtained with 
rain-water. If an insufficient quantity such as 8 or 10 grains 
only instead of 40, carmine will be produced, but of a bad 
quality, and of a dull crimsonish colour without lustre. If 25 
to 30, carmine as good or nearly so as with 40, the excess above 
what is necessary to decompose the alum and combine with the 
colouring principle going to the bottom with the dregs after the 
alum has been added. 
(2) If carbonate of barytas or carbonate of magnesia be 
substituted for the whitening, dirty coloured purplish precipitates 
are the result. 
(3) Ifa small quantity of ordinary carmine be burnt in a 
silver spoon over the flame of a spirit lamp, and the ashes 
digested in dilute nitric acid, filtered, and to the filtrate oxalate 
of ammonia and ammonia sufficient to neutralize the liquor be 
added, a copious precipitate falls, consisting of oxalate of lime 
and alumina, of which the alumina is taken up again on the 
addition of acetic acid. 
(4) Ifcarmine be dissolved in liquor ammonie diluted with 
about 3 times its weight of water, and the liquor filtered, a 
residue consisting apparently of lime and alumina remains. 
(5) If the filtrate be rendered strongly acid by acetic acid, 
a copious precipitate ensues of what is known by the name of 
“ precipitated carmine.” 
(6) If to the filtrate from which the precipitated carmine 
was separated, oxalate of ammonia be added, a precipitate of a 
