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BILIRUBIN. 431
in chloroform depends, according to Kuster, on the fact that in its
preparation, derivatives which are readily soluble and contain chlorine
or other transformation products are formed, or perhaps the bilirubin
goes over into polymeric modifications having different solubilities. In
cold dimethylaniline it dissolves in the proportion of 1:100, and in hot
dimethylaniline much more readily. Its solutions show no absorption-
Viands, but only a continuous absorption from the red to the violet end
of the spectrum, and they have a decided yellow color, even on diluting
greatly (1:500000), in .a layer 1.5 cm. thick. The combinations of
bilirubin with alkali are insoluble in chloroform, and the bilirubin in solu-
tion in chloroform can be removed from this solution by shaking with
dilute alkali (differing from lutein). Solutions of bilirubin-alkali in
water are precipitated by the soluble salts of the alkaline earths and also
by metallic salts. If a dilute solution of alkali bilirubin in water is
treated with an excess of ammonia and then with a zinc-chloride solution,
the liquid is first colored deep orange and then gradually olive-brown
and then green. This solution first gives a darkening of the violet and
blue part of the spectrum, and then the bands of alkaline cholecyanin
(see below), or at least the bands of this pigment in the red between
C and D, close to C. This is a good reaction for bilirubin. The fol-
lowing reaction has been suggested by Auche l
. Treat 5 cc. of an alcoholic
solution of bilirubin (1:20000) which contains 1 drop of ammonia in
100 cc, with 5 to 6 drops of an alcoholic zinc acetate solution (1:1000)
and then 1 drop alcoholic iodine solution (1:100) when a beautiful bluish-
green coloration with a beautiful garnet-red fluorescence is obtained on
shaking. The spectrum shows a dark band between B and C, and a
pale band at D. If a few drops of hydrochloric acid are added to the
solution the color becomes violet, the fluorescence disappears and the
two Jaffa’s cholecyanin bands appear. This reaction is extremely
delicate.
As Ehrlich first showed, bilirubin forms combinations with diazo
compounds, which have been closely studied by Proscher, Orndorff
and Teeple.2
A test suggested by Ehrlich for bilirubin is based upon
this behavior with sulphodiazobenzene.
If an alkaline solution of bilirubin be allowed to stand in contact
with the air, it gradually absorbs oxygen, and green biliverdin is formed.
This process is accelerated by warming. According to Kuster, in this
case the alkali also has a splitting action upon the pigment, and among
the products formed we find hsematinic acid. Biliverdin is formed only
1
Compt. rend. soc. biol., 64.
2
Ehrlich, Zeitschr. f. anal. Chem., 23; Proscher, Zeitschr. f. physiol. Chem., 39;
Orndorff and Teeple, 1. c.
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