88 
PROXIMATE PRINCIPLES OF VEGETABLES. 
These experiments, although without satisfactory results, 
were nevertheless continued until 1S40, when I gave up 
the use of chemical reagents, and resolved to try some sub- 
stance which, possessing both a chemical and mechanical 
action, would have a kind of elective affinity, so as to seize 
hold of certain substances and eliminate others. After nu- 
merous experiments, I tried animal charcoal with perfect 
success. My first experiments with this reagent were made 
on a spirituous extract of Digitalis. The solution, which 
was not very highly coloured, having been previously pre- 
cipitated with acetate of lead and filtered, was agitated with 
animal charcoal and the flask containing the mixture set 
aside; to my great astonishment, the liquid, on depositing 
the charcoal, had become not merely colourless, but had en- 
tirely lost its bitter taste. I decanted the liquid and washed the 
charcoal with distilled water, dried it in the stove, and then 
treated it with boiling alcohol, which acquired a pale tint, 
and took up the whole of the bitter principle. The alcohol, 
on evaporation in the water-bath, left at the bottom of the 
vessel an amber-coloured liquid, which deposited a pulveru- 
lent substance, the quantity of which increased after some 
time and cooling. This new substance, separated and 
washed, dissolved in alcohol, and furnished by its sponta- 
neous evaporation crystals of digitaline. The crystals dis- 
solve, but in small quantity, in water, to which they com- 
municate a very bitter taste; they are more readily soluble 
in weak than in strong alcohol, and more so in hot than in 
cold. Ether has but little action upon digitaline. Both the 
alcoholic and the aqueous solution are neutral, as they have 
no action upon blue litmus-paper and upon that which has 
been reddened by an acid. 
Sulphuric acid dissolves digitaline, and this solution finally 
acquires suddenly a very beautiful purple colour. After a 
time this colour disappears, passing into a brown, and a 
precipitate forms in the liquid of a blackish substance, pro- 
duced by the decomposition of the proximate principle. If 
