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PYR0CATE0HIN-8ULPHURIC ACID. 727
cresol into dibromcresol under exactly observed conditions is deter-
mined and from the quantities of bromine by weight (Bi and B2 )
quantities by weight of phenol and cresol can be calculated. In regard to
the procedure as well as to the necessary solutions we refer to the original
publication.
The methods for the separate determination of the conjugated sul-
phuric acid and the sulphate-sulphuric acid will be spoken of later in
connection with the determination of the sulphuric acid of the urine.
Pyrocatechin-sulphuric Acid. This acid was first found in horse’s urine in
rather large quantities by Baumann. It occurs in human urine only in the very
smallest amounts, and perhaps not constantly, but it is present abundantly in
the urine after taking phenol, pyrocatechin, or protocatechuic acid.
With an exclusively meat diet this acid does not occur in the urine, and it
therefore must originate from vegetable food. It probably originates from the
protocatechuic acid, which, according to Preusse, passes in part into the urine
as pyrocatechin-sulphuric acid. This acid may also perhaps be formed by the
oxidation of phenol within the organism (Baumann and Preusse 1
).
Pyrocatechin, or o-Dioxybenzene, CeBuCOH)., was first observed in the urine
of a child (Ebstein and J. Muller). The reducing body alcapton, first found
by Bodeker - in human urine and which was considered for a long time as iden-
tical with pyrocatechin, is in most cases probably homogentisic acid (see below).
Pyrocatechin crystallizes in prisms which are soluble in alcohol, ether, and
water. It melts at 102-104° C, and sublimes in shining plates. The watery
solution becomes green, brown, and finally black in the presence of alkali
and the oxygen of the air. If very dilute ferric chloride is treated with tartaric
acid and then made alkaline with ammonia, and this added to a watery solution of
pyrocatechin, we obtain a violet or cherry-red liquid which becomes green on
adding excess of acetic acid. Pyroeateehin is precipitated by lead acetate. It
reduces an ammoniacal silver solution at the ordinary temperature, and with
heat reduces alkaline copper-oxide solutions but does not reduce bismuth oxide.
A urine containing pyrocatechin, if exposed to the air, especially when alkaline,
quickly becomes dark and reduces alkaline copper solutions when heated. In
detecting pyrocatechin in the urine it ie concentrated when necessary, filtered,
boiled with the addition of sulphuric acid to remove the phenols, and repeatedly
shaken, after cooling, with ether. The ether is distilled from the several ethereal
extracts, the residue neutralized with barium carbonate and shaken again with
ether. The pyrocatechin which remains after evaporating the ether may be
purified by recrystallization from benzene.
Hydroquinone, or p-Dioxybenzene, C6 H4 (OH) 2 , often occurs in the urine after
the use of phenol (Baumann and Preusse). The dark color which certain urines,
so-called " carbolic urines," assume in the air is due to decomposition products.
Hydroquinone does not occur as a normal constituent of urine, but only after
the administration of hydroquinone; and according to Lewin, 3
it may be found
in the urine of rabbits as an ethereal-sulphuric acid, being a decomposition product
of arbutin.
Hydroquinone forms rhombic crystals which are readily soluble in water,
alcohol, and ether. It melts at 169° C. Like pyrocatechin, it easily reduces
metallic oxides. It acts like pyrocatechin with alkalies, but is not precipitated
by lead acetate. It is oxidized into quinone by ferric chloride and other oxidiz-
1
Baumann and Herter, Zeitschr. f. physiol. Chem., 1; Preusse, ibid., 2; Baumann,
ibiii., 3.
- Ebstein and Muller, Virchow’s Arch., 62; Bodeker, Zeitschr. f. rat. Med. (3), 7.
3
Lewin, Virchow’s Arch., 92; Bass, Zeitschr. f. exp. Path. u. Ther., 10.
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