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726 URINE.
The alkali salts of phenol- and cresol-sulphuric acids crystallize in
white plates, similar to mother-of-pearl, which are rather freely soluble
in water. They are soluble in boiling alcohol, but only slightly soluble
in cold alcohol. On boiling with dilute mineral acids they are decom-
posed into sulphuric acid and the corresponding phenol.
Phenol-sulphuric acids have been synthetically prepared by Baumann
from potassium pyrosulphate and potassium phenolate or p-cresolate.
For the method of their preparation from urine, which is rather compli-
cated, and also for the known phenol reactions, the reader is referred
to other text-books. The quantitative estimation of the phenols from
these etheral sulphuric acids is now ordinarily done by the following
methods:
Kossler and Penny’s method with Neuberg’s x
modification. The
liquid containing phenol is treated with N/10 caustic soda until strongly
alkaline, warmed on the water-bath in a flask with a glass stopper, and
then treated with an excess of N/10 iodine solution, the quantity being
exactly measured. Sodium iodide is first formed and then sodium
hypoiodite, which latter forms tri-iodophenol with the phenol accord-
ing to the following equation:
C6N5OH+3NaIO = C6H2 I 3 .OH+3NaOH.
On cooling, acidify with sulphuric acid and determine the excess of iodine
by titration with N/10 sodium thiosulphate solution. This process is
also available for the estimation of paracresol. Each cubic centimeter
of the iodine solution used is equivalent to 1.5670 milligrams of phenol
or 1.8018 milligrams of cresol. As the determination does not give any
idea as to the variable proportions of the two phenols, the quantity of
iodine used must be calculated as one or the other of the two phenols.
Before such a determination is carried out, the concentrated urine is
first distilled after acidification with sulphuric acid and the distillate
purified by precipitation with lead, and distilled again (Neuberg).
Mooser has raised objections against the use of sulphuric acid and rec-
ommends instead the use of phosphoric acid. In regard to the dispute
which has arisen between Neuberg and Mooser 2
as well as to the details
of Neuberg’s method we must refer to the original publications and to
larger handbooks.
For the separate estimation of phenol and p-cresol in the urine a
special method has been suggested by Siegfried and Zimmermann.3
The principle of the method consists in the two following estimations:
1. The quantity of bromine necessary to convert the phenol and cresol
into tribromphenol and tribromcresol is determined. 2. The quantity
of bromine necessary to convert the phenol into tribromphenol and the
1
Kossler and Penny, Zeitschr. f. physiol. Chem., 17; Neuberg, ibid., 27.
2
Mooser, Zeitschr. f. physiol. Chem., 63, with Liechti, ibid., 73; Neuberg and
Hildesheimer, Bioch. Zeitschr., 28; Marie Hensel, Zeitschr. f. physiol. Chem., 78.
3
Siegfried and Zimmermann, Bioch. Zeitschr., 29, 34 and 38; see also Ditz and Bar-
dach, ibid., 37 and 42.
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