Art. XXXI.—On the examination of the Bark of Coprosma Grandifolia, for Alkaloids.
[Read before the Wellington Philosophical Society, July 17, 1869.]
The sample I tested was named by Mr. Buchanan, at the time of collecting; it has a bright yellow colour on its inner surface, is very bitter, with a slightly hot pungent flavour. It is decidedly the bitterest of any of the barks of this family, which were pointed out to me, and for this reason I made choice of it for experiment.
The following is a brief summary of the results obtained:—it shows by an easy, simple, and I think a reliable process, that alkaloids, generally, and those of the Quina group in particular, are either entirely absent, or present only in so minute a quantity, that the bark is quite worthless as a drug, on this account at least.
A decoction of 200 grammes of the pulverized bark, in weak hydrochloric acid, was slowly evaporated to a bulk of half-an-ounce, then filtered; the filtrate did not give any precipitate with the following re-agents:
Sulphocyanide of mercury.
Sulphocyanide of zinc.
These substances are capital tests for the alkaloids generally, giving dense precipitate in a very weak decoction, even, of the common Gray bark.