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746 URINE.
yellow, or (the ammoniacal) yellowish green, according to concentration.
They show a dark band 7, which is moved somewhat toward the red
end of the spectrum and lies between E and F. The absorption max-
imum lies at X = 506-510. If some zinc-chloride solution is added to
an ammoniacal solution of the pigment it becomes red and shows a
beautiful green fluorescence and gives the same absorption bands. If
a sufficiently concentrated solution of urobilin alkali is carefully acidified
with sulphuric acid it becomes cloudy and shows a second band exactly
at E, and connected with 7 by a shadow (Garrod and Hopkins, Saillet x
).
Urobilinogen is colorless or only faintly colored, but is very quickly
changed in the air and bythe actionof light and is transformed into urobilin.
The urobilinogen, which is identical with hemibilirubin, can be obtained
as colorless prisms by solution in hot acetic-ether and treating this with
ligroin, and evaporating. Urobilinogen is soluble in ether, acetic ether,
amyl alcohol and in chloroform, and can in part be removed from the
urine after adding sodium bicarbonate and shaking with chloroform
(Fischer and Meyer-Betz). It can also be obtained directly from the
urine or from the acidified urine by shaking with chloroform or ether,
although it is less pure. In a chloroform solution of urobilin and urobilino-
gen, according to Grimbert 2
, only urobilin and not urobilinogen is
taken up by a sodium diphosphate solution, which is not colored red by
phenolphthalein. Like urobilin, it is precipitated from the urine on
saturating with ammonium sulphate. When free from urobilin it does
not give auy absorption bands and no fluorescence with ammonia and
zinc salt. For the detection and identification of urobilinogen we make
use of Ehrlich’s reagent (p-dimethylamino-benzaldehyde). This
reagent consists of dissolving 2 grams p-dimethylaminobenzaldehyde
in 50 cc. concentrated, fuming hydrochloric acid and diluting to 100
cc. with water. To 10 cc. of the urine add 1 cc. of the reagent and
thoroughly shake. According to the amount of urobilinogen, the solution
becomes pink colored or intensely red, and in the spectrum we find a
band between D and E. The red color can be taken up by amyl alcohol.
Urobilin does not give this reaction, which is common to certain haematin
and pyrrol derivatives.
The preparation of urobilin from the urine can be done according to the
original method of Jaffe, or according to the method suggested by Mehu,
which has been modified somewhat by Garrod and Hopkins 3
(precipita-
tion with ammonium sulphate) or according to Charnas* suggestion.
According to Charnas 4
the preparation is best from urobilinogen,
1
Garrod and Hopkins, Journ. of Physiol., 20; Saillet, 1. c.
I -’her and Meyer-Betz, 1. c; Grimbert, Compt. rend. soc. biol., 70.
» Jaffe\ 1. c; Mehu, 1. c; Garrod and Hopkins, Journ. of Physiol., 20.
* Charnas, Bioch. Zeitschr., 20.
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