rt of
the water removed under the form of ice; but this is liable to all the
former objections; and, besides, where lemons are produced in sufficient
quantity, there is not a sufficient degree of cold. The addition of a
portion of spirit to the inspissated juice, separates the mucilage, but
not the extractive matter and the sugar. By means, however, of
separating the foreign matters associated with it, in the juice, by
chemical processes unnecessary to be detailed here, citric acid is now
manufactured, perfectly pure, and in a crystallised form, and is sold
under the name of concrete lemon acid. In this state it is extremely
convenient, both for domestic and medicinal purposes. One drachm, when
dissolved in one ounce of water, is equal in strength to a like bulk of
fresh lemon juice. To communicate the lemon flavour, it is only
necessary to rub a lump of sugar on the rind of a lemon to become
impregnated with a portion of the essential oil of the fruit, and to add
the sugar to the lemonade, negus, punch, shrub, jellies or culinary
sauces, prepared with the pure citric acid.

Fraudulent dealers often substitute the cheaper tartareous acid, for
citric acid. The negus and lemonade made by the pastry-cooks, and the
liquor called punch, sold at taverns in this metropolis, is usually made
with tartareous acid.

To discriminate citric acid from tartareous acid, it is only necessary
to add a concentrated solution of the suspected acid, to a concentrated
solution of muriate of potash, taking care that the solution of the acid
is in excess. If a precipitate ensues, the fraud is obvious, because
citric acid does not produce a precipitate with a solution of muriate
or potash.

Or, by adding to a saturated solution of tartrate of potash, a saturated
solution of the suspected acid, in excess, which produces with it an
almost insoluble precipitate in minute granular crystals. Pure citric
acid produces no such effect when added in excess to tartrate of
potash.

_Poisonous Mushrooms._

Mushrooms have been long used in sauces and other culinary preparations;
yet there are numerous instances on record of the deleterious effects of
some species of these _fungi_, almost all of which are fraught with
poison.[114] Pliny already exclaims against the luxury of his countrymen
in this article, and wonders what extraordinary pleasure there can be in
eating such dangerous food.[115]

But if the palate must be indulged with these tre