he suspected leaves, should be infused in half-a-pint of
cold, soft water, and suffered to stand for about an hour. Genuine tea
produces an amber-coloured infusion, which does not become reddened by
sulphuric acid.

All the samples of spurious green tea (nineteen in number) which I have
examined, were coloured with carbonate of copper (a poisonous
substance,) and not by means of verdigris, or copperas.[87] The latter
substances would instantly turn the tea black; because both these
metallic salts being soluble in water, are acted on by the astringent
matter of the leaves, whether genuine or spurious, and convert the
infusion into ink.

Tea, rendered poisonous by carbonate of copper, speedily imparts to
liquid ammonia a fine sapphire blue tinge. It is only necessary to shake
up in a stopped vial, for a few minutes, a tea-spoonful of the suspected
leaves, with about two table-spoonsful of liquid ammonia, diluted with
half its bulk of water. The supernatant liquid will exhibit a fine blue
colour, if the minutest quantity of copper be present.

Green tea, coloured with carbonate of copper, when thrown into water
impregnated with sulphuretted hydrogen gas, immediately acquires a black
colour. Genuine green tea suffers no change from the action of these
tests.

The presence of copper may be further rendered obvious, by mixing one
part of the suspected tea-leaves, reduced to powder, with two or three
parts of nitrate of potash, (or with two parts of chlorate of potash,)
and projecting this mixture by small portions at a time, into a platina,
or porcelain-ware crucible, kept red-hot in a coal fire; the whole
vegetable matter of the tea leaves will thus become destroyed, and the
oxide of copper left behind, in combination with the potash, of the
nitrate of potash (or salt-petre,) or with the muriate of potash, if
chlorate of potash has been employed.

If water, acidulated with nitric acid, be then poured into the crucible
to dissolve the mass, the presence of the copper may be rendered
manifest by adding to the solution, liquid ammonia, in such quantity
that the pungent odour of it predominates.

FOOTNOTES:

[85] Also, 2 Geo. I, c. 30, Sec. 5; and 4 Geo. II, c. 14, Sec. 11.

[86] The examination of twenty-seven samples of imitation tea of
different qualities, from the most costly, to the most common, which it
fell to my lot to undertake, induces me to point out the marks of
sophistications here detailed, as the most