important constituent of some urines, is not affected by picric acid,
and the test is decidedly one of great value.

The _nitric acid test_. Heller's contact method, which can also be
used with the last-described reagent, is the best mode of applying the
old-fashioned and favorite test with nitric acid. To 5 volumes of a
filtered saturated solution of magnesic sulphate, prepared by
dissolving 10 parts of the salt in 13 parts of distilled water, add 1
volume of strong nitric acid, and label "Sir W. Roberts' nitric acid
reagent." A couple of drachms of bright filtered urine is allowed to
float on an equal quantity of this solution in a test tube; care being
taken that the contact line is sharply defined. In a period of time
varying from a few seconds to a quarter of an hour, according to the
amount of albumen present, a delicate opalescent zone forms at the
point of junction, and if mucin also is present, a more diffused haze
higher up in the urine. Special attention should be given to the
position of the opacity. In some concentrated urines a belt of urates
will appear at the line of demarkation; but these dissolve on warming.
Moreover, owing to the dilution necessary in the mode of applying
Galippe's picric acid test, they are not so readily shown by the
latter. A ½ oz. glass syringe can very conveniently be substituted for
a test tube in making analyses according to Heller's method. Some of
the urine should be drawn up, and then an equal volume of the reagent.
On setting aside, the albumen ring will rapidly develop.

The _boiling test_. This method also is very delicate and valuable. It
depends on the well-known property possessed by many proteids of
coagulating under the influence of heat. The urine should have an acid
reaction to test paper; if alkaline, it must be cautiously neutralized
with dilute acetic acid. In either case a single drop of strong acetic