NOTE UPON COFFEE. 
227 
yellow colour, possessing the taste and smell of green coffee. 
This oil readily combines with caustic alkalies, and forms a 
hard soap, becoming coloured reddish brown, in consequence 
of the reaction of the alkali upon a colouring principle con- 
tained in the oil, which becomes developed only by time. 
The proportion of this oil does not exceed two ounces to the 
pound J and it is evident, from what has been stated, that it 
exists in the very interior of the grain, while the exterior 
surface is simply invested with a layer of vegetable wax. It 
should be remarked that the ethereal tinctures, last obtained, 
abstracted with the oil a white substance, which concreted 
upon evaporation — and which could be separated from the oil 
by the filter while warm. What remained upon the filter 
being compressed between bibulous paper and then dissolved 
in boiling water and refiltered, a fibrous crystallization due to 
the caffein was obtained by refrigeration. 
The filter retained a whitish granular substance, which 
resisted the action of boiling water; and which, nevertheless, 
placed upon a plate of platina and heated, was liquified and 
gave out the smell of fish oil. It also sometimes happened, that 
we saw in the product of the evaporation of these last ethereal 
tinctures, a small number of yellow shining minute crystals 
which emitted, when burned upon a piece of platina, the 
marked odour of sulphurous acid, and exhibited a blue flame. 
Coffee, then, contains a small quantity of sulphur. 
Desirous of ascertaining whether the odour and taste of 
green coffee, which the fixed oil manifests, do not depend 
upon an essential oil that it contains, we boiled a small quan- 
tity of it in a distilling apparatus ; and we obtained as the 
product a slightly lactescent water, having a feeble smell of 
horse-radish. 
After having exhausted the cofiee with ether, we employed 
alcohol at difierent degrees, 40°, 36°, 22°. Each of these 
vehicles was employed both hot and cold, but not having 
obtained any result worthy of being cited, we took another 
quantity of coffee equally exhausted by ether, and we submit- 
ted it to three successive decoctions in distilled water. All 
