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PROTEIDS IN THE URINE. 789
A confounding with mucin, when this body occurs in the urine, is
easily prevented in the heat test with acetic acid by acidifying another
portion with acetic acid at the ordinary temperature. Mucin and
nucleoalbumin substances similar to mucin arc hereby precipitated. If
in the performance of the heat and nitric-acid test, a precipitate first
appears on cooling or is strikingly increased, then this -hows the presence
of proteoses in the urine, either alone or mixed with coagulable proteid.
In this case a further investigation is necessary (see below). In a urine
rich in urates a precipitate consisting of uric acid separates on cooling.
This precipitate is colored and granular, and is hardly to be mistaken
for a proteose or proteid precipitate.
Heller’s test is performed as follows (see page 99): The urine is
very carefully floated on the surface of nitric acid in a test-tube, or the
urine is placed in a test-tube and then the acid is slowly added by means
of a funnel, drawn out to a point, and extending to the bottom. In the
presence of albumin a white disk, or as we ordinarily say a white ring or
at least a sharply defined cloudiness, appears at the point of contact of
the two fluids. With this test a red or reddish-violet transparent ring
is always obtained with normal urine; it depends upon the indigo color-
ing-matters and can hardly be mistaken for the white or whitish proteid
ring. In a urine rich in urates, another complication may occur, due
to the formation of a ring produced by the precipitation of uric acid.
The uric-acid ring does not lie, like the proteid ring, between the two
liquids, but somewhat higher. For this reason two simultaneous rings
may exist in urines which are rich in urates and do not contain very much
proteid. The disturbance caused by uric acid is easily prevented by
diluting the urine with 1-2 vols, of water before performing the test.
The uric acid now remains in solution, and the delicacy of Heller’s
test is so great that after dilution only in the presence of insignificant
traces of proteid does this test give negative results. In a urine very
rich in urea a ring-like separation of urea nitrate may also appear. This
ring consists of shining crystals, and it does not appear in urine previously
diluted. A confusion with resinous acids, which also give a whitish
ring with this test, is easily prevented, since these acids are soluble on the
addition of ether. Stir, add ether, and carefully shake the contents of
the test-tube. If the cloudiness is due to resinous acids, the urine gradually
becomes clear, and on evaporating the ether a sticky residue of resinous
acids is obtained. A liquid which contains true mucin does not give
a precipitate with this test, but it gives a more or less strongly opalescent
ring, which disappears on stirring. The liquid does not contain any
precipitate after stirring, but is somewhat opalescent. If a faint, not
wholly typical reaction is obtained with Heller’s test after some time
with undiluted urine, while the diluted urine gives a pronounced reaction,
the presence is shown of the substance which used to be called mucin
or nucloealbumin. In this case proceed as described below for the detec-
tion of nucleoalbumin.
If the above-mentioned possible errors and the means by which they
may be prevented are borne in mind, there is hardly another test for
proteid in the urine which is at the same time so easily performed, so
delicate, and so positive as Heller’s. With this test even 0.002 per
cent of albumin may be detected without difficulty. »>till the student
must not be satisfied with this test alone, but should apply at least a
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