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 1/2 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
acid should be added to about three drachms of the bright liquid. If
this precaution is omitted, there is danger of precipitating earthy
phosphates on heating; and should a great excess of acid be employed,
a non-coagulable form of albumen known as syntonin is formed, besides
increasing the likelihood of precipitating mucin.
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