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808 URINE.
chloride has disappeared. After standing sufficiently long the ester is collected,
finely divided, and saponified with an alcoholic solution of sodium ethylate in the
cold according to Baisch’s method, 1
and the various carbohydrates separated
according to his suggestion.
If small quantities of sugar are to be isolated from the urine, precipitate the
urine first with sugar of lead, filter, precipitate the filtrate with ammoniacal
basic lead acetate, wash this precipitate with water, decompose it with H2 S when
suspended in water and use the filtrate for the special tests. Schondorff 2
has suggested a method for the detection and estimation of very small amounts
of sugar based upon the work of Patein and Dufau. This method depends
upon precipitating the nitrogenous substances with mercuric nitrate.
To the physician, who naturally wants simple and quick methods,
the bismuth test is especially to be recommended. If this test gives neg-
ative results, the urine is to be considered as free from sugar in a clinical
sense. If it gives positive results, the presence of sugar must be con-
trolled by other tests, especially by the fermentation test.
Other tests for sugar, as, for example, the reaction with orthonitrophenyl-
propiolic acid, picric acid, diazobenzene-sulphonic acid, are superfluous. The
reaction with a-naphthol, which is a reaction for carbohydrates in general, for
glucuronic acid and mucin, may, because of its extreme delicacy, give rise to
mistakes, and is therefore not to be recommenced to physicians. Normal urines
give this test, and if the strongly diluted urine gives the reaction the presence
of great quantities of carbohydrates may be suspected. In these cases more
positive results are obtained by using other tests. This test requires great clean-
liness, and it has the inconvenience that sufficiently pure sulphuric acid is not
always readily procurable. Several investigators, such as v. Udransky, Luther,
Roos and Treupel, 3
have investigated this test in regard to its applicability
as an approximate test for carbohydrates in the urine.
Quantitative Determination of Sugar in the Urine. The quantity of
sugar can be determined by titration, by fermentation of the sugar, by
-polarization, and also in other ways.
The titration methods are based upon the property of the sugar to
reduce metallic oxides in alkaline solutions. As the titration liquids
(cupric oxide solution in the Fehling-Soxhlet, Pavy, Bang, Bertrand
methods and mercuric oxide in Knapp’s method) are also reduced by
other urinary constituents, these reduction methods always give too high
results. When large quantities of sugar are present, as in typical
diabetic urine, which generally contains a lower percentage of normal
reducing constituents, this is indeed of little account; but when small
quantities of sugar are present in an otherwise normal urine, the mistake
may, on the contrary, be important, as the reducing power of normal
urine may correspond to 5 p. m. glucose (see page 749). In such cases
the titration procedure must be employed in connection with the fer-
mentation method, which will be described later.
1
Zeitschr. f. physiol. Chem., 19.
J
Pfluger’s Anh., 121, which cites the work of Patein and Dufau.
1
See Roos and Treupel, Zeitschr. f. physiol. Chem., 15 and 16.
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