Ixxii Historical Sketch of the Physical Sciences, 1818. 
éharacters by which he has distinguished it are not accurate. 
The method which Pelletier and Caventon took to obtain the 
¢armine in a state of purity was to digest the cochineal insect 
in alcohol, as long as it gave a red colour to that liquid. These 
solutions, when left to spontaneous evaporation, let fall a crystal- 
line matter of a fine red colour, consisting of the carmine; but 
hot in a state of purity. To obtain it pure, these crystals were 
dissolved in strong alcohol, and the liquid was mixed with its 
own bulk of sulphuric ether. It became muddy, and after an 
interval of some days the carmine was deposited at the bottom 
‘of the vessel, forming a beautiful purplish red crust; the 
liquor was become perfectly clear, and had a yellowish red co- 
four. The properties of the carmine thus obtained are as 
follows : 
~ It has a fine purple red colour. It adheres strongly to the 
sides of the vessel in which it is deposited. It has a granular 
‘appearance, as if it were composed of crystals. It is not altered 
‘by exposure to the air. It does not absorb any sensible quantity 
of moisture. "When heated to the temperature of 122° it melts. 
If the heat be increased, it swells up and is decomposed, yield- | 
ing carburetted hydrogen gas, a great deal of oil, and a little 
water, having a slightly acid taste. It gives out no traces of 
ammonia. 
It is very soluble in water. The liquid may be reduced by 
evaporation to the consistency of a syrup; but the carmine 
does not crystallize. The watery solution of it has a fine car- 
mine red colour. A very small portion of this substance gives 
a strong colour to a great quantity of water. It is soluble like- 
wise in alcohol; but the stronger the alcohol is, the worse a 
solvent does it become. It is insoluble in sulphuric ether ; the 
weak acids dissolve it ; but probably merely in consequence of 
the water which they contain. No acid precipitates it when 
ptre ; but they almost all throw it down when it is in combination 
with the peculiar animal matter of the cochineal ; but all the 
acids produce a sensible change upon the aqueous solution of 
carmine. They make it assume in the first place a hively red 
colour, which gradually assumes a yellowish tinge, and at last 
becomes entirely yellow, When the acids are not very concen- 
trated, the carmine is not altered in its nature; for when the 
acid is saturated, the colour resumes its former appearance. 
’ Concentrated sulphuric acid destroys and chars carmine. 
Muriatic acid decomposes it without charing it, and converts it 
into a bitter substance, which has no resemblance to carmine. 
“Nitric acid decomposes-it with still greater rapidity. Some 
‘needle-form crystals are formed similar in appearance to oxalic 
acid ; but they do not precipitate lime-water even when mixed 
with ammonia. The nature of these crystals was not ascertained, 
Chlorine acts with energy-on carmine, giving it first a yellow 
colour, which it gradually destroys altogether. It occasions no 
