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formation of the c. carminate of lime and alumina which, I take 
it, is the most essential part of carmine, if not all that carmine 
consists of; but if that were the only use of the lime, carbonate 
of magnesia or of barytas would answer as well, and as I have 
just observed, they do not. As to the salts of tin, the 
chlorides throw down crimson and reddish lakes, drying up 
into hard brittle substances from both the p. and ec. carminates of 
ammonia. The ec. carminic acid is probably decomposed by 
bichloride of tin. Actinic influences have nothing to do with 
the success of the operation; I have made as good carmine in 
dull days as in bright ones, nor, if the vessels are clean, as they 
should be, (for that is of primary importance, the slightest rust 
or impurity being evidenced by a degradation in the tint of the 
product,) is failure possible. The notion that fine weather is 
favourable to carmine making, may arise from the fact, that 
in fine dry weather, river water holds more lime in solution than 
when diluted by copious rains. With the exception of the 
carmine made years ago by the English firm of Berger, the best 
I believe has been made in France, and at Rouen, and the river 
Seine is saturated with chalk. The latest investigation into the 
colouring matter of cochineal is I believe that published by 
De la Rue. His carminic acid must (I imagine from the résumé 
of his results given in “Chemistry as applied to the Arts” by 
Dr Muspratt) be the same as what I call purpureo carminic acid. 
The combining numbers of c. carminic and p. carminic acids 
would be best determined from their lead compounds, but for 
this purpose an accurate Liebig’s apparatus and a good pair of 
scales are necessary, and my appliances are of the rudest and 
homeliest kind. IJ cannot lay claim to any great skill or ex- 
perience as a practical or even theoretical chemist, but my ex- 
periments imperfect as they are, will I think be sufficient to 
prove the thesis I have advanced, viz. that of the existence of 
two colouring principles in cochineal, and of lime in carmine, 
and may perhaps draw the attention of abler chemists than 
