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CARBAMIC ACID. G91
In regard to other met lux Is such as Bunben’s method with its man.
modifications as suggested by Pfluger, Bohland and Bleibtreu,
we refer to more complete handbooks.
For the quantitative estimation of urea in blood or other animal
fluids, as well as in the tissues. ScHONDOBFF has proposed a method
where the proteins and extractives are first precipitated by a mixture
of phosphotungstic acid and hydrochloric acid, and then the filtrate
made alkaline with lime. The quantity of ammonia formed on heating
a part of this filtrate to 150° C. with phosphoric acid and the amount
of carbon dioxide produced by heating the other part to 150° C. are
determined. In regard to the principles of this method, as well a- to
the details, we refer to the original article (Pfluger’s Arch., (>2). Sal-
cowski ’
has recently suggested a method for estimating the urea in
tissues.
Urein is the name given by Ovid Moor to a product which he obtained by
extracting urine, which had been evaporated to a syrup, with absolute alcohol
and precipitating the urea with alcohol containing oxalic acid, or by cooling and
treatment with alcohol. Urein is a golden-yellow oil which is poisonous; it
reduces permanganate in the cold, and it forms the chief portion of the nitro-
genous extractives of urine. There is no doubt that urein is a mixture of several
substances. According to Moor,2
the amount of urea in the urine is only about
one-half that ordinarily given, and he has suggested a new method for the deter-
mination of the true quantity of urea. The possibility that in the urine we have
other bodies besides urea which have been determined with the urea cannot be
denied a priori. From the investigations published so far it must be said that
Moor’s assertions are not sufficientlv grounded. 3
/XH2
Carbamic Acid, CH3XOj=CO< . This acid is not known in the free
xOH
state, but only as salts. Ammonium carbamate is produced by the action of
dry ammonia on dry carbon dioxide, but also after the addition of Xa.-C’O, to a
solution which contains an ammonium salt (Macleod and Haskixs). Carbamic
acid is also produced by the action of potassium permanganate on protein and
several other nitrogenous organic bodies.
The occurrence of carbamic acid in human and animal urines has already
been considered in connection with the formation of urea. The calcium salt
which is soluble in water and ammonia but insoluble in alcohol, is the most impor-
tant in the detection of this acid. The solution of the calcium salt in water
becomes cloudy on standing, but much more quickly on boiling, and calcium car-
bonate separates. Xolf, Macleod and Haskixs have made experiments as to
the method of formation of carbamic acid. The latter have indicated a new
method for the quantitative estimation of carbamates. 4
1
Arbeiten aus deni pathol. Institute, Berlin, 1906.
2
0. Moor, BuM. Acad, de St. Petersbourg, 14 (also Maly’s Jahresber., 31, 415),
and Zeitschr. f. Biologie, 44 and 45, and Zeitschr. f. physiol. Cheai., 41) and 48.
3
See Kuliabko. Maly’s Jahresber., 31, 415; Erben, Zeitschr. f. physiol. Chem.,
38; Folin, ibirl., 37; Gies, Journ. Amer. Chem. Soc, 25; Haskins, Anier. Journ. of
Physiol., 12; Lippich, Zeitschr. f. physiol. Chem., 48 and 52.
4
Xolf, Zeitschr. f. physiol. Chem., 23; Macleod and Haskins, Amer. Journ. of
Physiol., 12, and Journ. of biol. Chem., 1.
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