A. Treat the filtered liquid with carbonate of potass.
B. Add a solution of sulphate of iron with a small quantity of alum: a precipitate, as in the former method, will fall down, which if treated by free sulphuric acid, will also become blue and pulverulent. During this latter part of the experiment, there is a disengagement of carbonic acid.
Evidence may be pushed still farther, and the existence of the Prussic acid proved in a most positive manner by decomposing the precipitate, above described, and which is a true Prussian blue, so as to separate the acid. For this purpose, heat the precipitate with an equal quantity of tartaric acid, in a glass retort, at the temperature of 150°, when the hydro-cyanic vapours will soon exhale from the mixture, and may be received in water.”[[442]]
Cl. V. NARCOTICO-ACRID POISONS.
We have already stated our objections to this division, and our apology for adopting it. See page [205].
Deadly Nightshade. Atropa Belladonna.
(Pentandria Monogynia. Nat. Ord. Luridæ Linn. Solanaceæ. Juss.)
This plant is an indigenous perennial, found in many parts of Great Britain, particularly in shady places where the soil is calcareous, in large ditches, and on the edge of hilly woods; flowering in June, and ripening its berries in September. Every part of the plant is poisonous; and numerous instances have occurred where children, and the ignorant, or those suffering from hunger, allured by the beautiful and tempting appearance of the berries, have fallen victims to their deadly power. The root of this plant partakes also of the same qualities as the leaves and berries, but is perhaps less virulent.
“Or have we eaten of the insane root,
That takes the reasoner prisoner.”—Macbeth.
The inspissated juice (Extractum Belladonnæ Pharm. Lond.) is also extremely poisonous, when properly prepared; but, as usually met with in commerce, it is of very variable strength; when prepared according to the improved process of Mr. Barry, its activity is so considerable that a dose of two grains is followed by unpleasant effects. (See an account of its effects in the Pharmacologia, vol. 2, p. 199.) M. Brandes has lately ascertained that the active principle of this plant is a peculiar alkaline body, to which he has assigned the name of atropia.