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ESTIMATION OF SUGAR IN URINE. 813
chloric acid or sulphuric acid. The activity of the yeast must, when,
necessary, be controlled by a special test. Place 200 cc. of the urine
in a 400 cc. flask, add a piece of compressed yeast the size of a pea, and
subdivide the yeast through the liquid by Bhaking; close the flask with
a stopper provided with a finely- drawn-out glass tube, and allow the test
to stand at the temperature of the room or, still better, at 30-35° C.
After twenty-four hours the fermentation is ordinarily ended, but this
must be verified by the bismuth test. After complete fermentation filter
through a dry filter, bring the filtrate to the proper temperature, and
determine the specific gravity.
If the specific gravity be determined with a good pycnometer sup-
plied with a thermometer and an expansion-tube, this method, when the
quantity of sugar is not less than 0.4-0.5 per cent, gives, according to
Worm-Muller, very exact results, but this has been disputed by Budde. 1
For the physician the method in this form is not serviceable. Even when
the specific gravity is determined by a delicate urinometer which can
give the density to the fourth decimal, exact results are not obtained,
because of the ordinary errors of the method (Budde); but the errors
are usually smaller than those which occur in titrations made by unskilled
hands.
When the quantity of sugar is less than 1.5 per cent, these methods
cannot be used. Such small amounts cannot, as already mentioned,
be determined by titration directly, because of the reducing power of nor-
mal urine. In such cases, it is better to first determine the reducing power
of the urine by titration according to Bang or Knapp, then ferment the
urine with the addition of yeast and titrate again. The difference
found between the two titrations calculated as sugar gives the true
quantity of the latter.
The determination of the sugar by fermentation can be so performed
that the loss in weight due to the CO2 can be estimated, or the volume
of the gas measured. For this last purpose Lohnstein 2
has constructed
a special fermentation saccharometer, and his " precision saccharometer
"
is to be recommended. Based upon Lohnstein ’s instrument, Wag-
ner 3
has constructed a "fermentation saccharo-manometer," which
has certain advantages over Lohnstein’s apparatus.
Estimations of Sugar by Polarization. In this method the
urine must be clear, not too deeply colored, and, above all, must not
contain any other optically active substances besides glucose. The
urine may contain several levorotatory substances such as proteids,
0-oxybutyric acid, conjugated glucuronic acids, the so-called Leo’s sugar
and less often cystine, all of which are unfermentable. The proteid is
removed by coagulation, and the others are detected by the polariscope
after complete fermentation. The fermentable fructose is detected in a
special manner (see below), and the dextrorotatory milk-sugar differs
from glucose in its not fermenting readily. By using a delicate instru-
1
Roberts, The Lancet, 1862; Worm-Muller, Pfluger’s Arch., 33 and 37; Budde,
ibid., 40, and Zeitschr. f. physiol. Chem., 13. See Lohnstein, Pfluger’s Arch., 62.
2
Berlin, klin. Wochenschr., 35, and Allg. med. Central-Ztg., 1899; Goldman, Chem.
Centralbl., 1907, 1, 1149.
’ Munch, med. Wochensch., 1905.
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