of the precipitate
may be ascertained. The fourth part of this weight is equivalent to the
weight of the muriatic acid contained in the portion of water
precipitated.

EXPERIMENT.

Precipitate the third portion of the water by the addition of oxalate of
ammonia; wash and dry the precipitate; expose it to a red heat, on a
platina foil, or in a capsule of platina; pour on it some dilute
sulphuric acid; digest for some time, then evaporate to dryness, expose
the capsule to a pretty strong heat, and, lastly, weigh the sulphate of
lime thus produced: 0.453 of its weight indicate the quantity of lime in
the portion of water precipitated.

EXPERIMENT.

Add to the same third portion of the water thus freed from lime, a
portion of a solution of neutral carbonate of ammonia, and then add
phosphoric acid, drop by drop, as long as any precipitate falls down.
Wash the precipitate, dry it, and expose it to a red heat in a platina
capsule: it is phosphate of magnesia. 0.357 of the weight of this salt
is equivalent to the weight of the magnesia contained in the water.

EXPERIMENT.

If the water contain a minute portion of iron, a quantity of it equal to
one of the three preceding portions, must be taken and mixed with a
solution of benzoate of ammonia. The precipitate being washed, dried,
and exposed to a red heat, and weighed, nine-tenths of its weight
indicate the weight of protoxide of iron contained in the water.

In this manner the quantity of all the substances contained in the water
will be ascertained, except there be any soda. To know the amount of it,
the following method, pointed out by Dr. Murray, answers very well.

EXPERIMENT.

Evaporate a portion of the water to one third of its bulk. Precipitate
the carbonic and sulphuric acids by the addition of muriate of barytes,
taking care not to add any excess of the tests.

Precipitate the lime by oxalate of ammonia, and the magnesia by
carbonate of ammonia and phosphoric acid. (Page 52.) Then evaporate the
liquid thus treated to dryness. A quantity of common salt will remain:
let this be exposed to a red heat; 0.4 of its weight indicate the sodium
contained in the bulk of water employed; and 0.4 sodium are equivalent
to 0.53 of soda.

It seems hardly requisite to mention some other substances that
occasionally make their appearance in the waters used for domestic
purposes. A fine divided sand is a common constituent, which is easily
obtained in a separate