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192 THE PROTEIN SUBSTANCES.
formed, which when dried at 120° C. has a constant composition,
2(C5HoAg2N40)H20, and is used in the quantitative estimation of
hypoxanthine. Hypoxanthine picrate is soluble with difficulty, but
if a boiling-hot solution of it is treated with a neutral or only faintly
acid solution of silver nitrate the hypoxanthine is almost quantitatively
precipitated as the compound C5H3AgN40.C6H2 (N02)30H. Hypo-
xanthine does not yield an insoluble compound with metaphosphoric
acid. When treated, like xanthine, with nitric acid, it yields, an almost
colorless residue which, on warming with alkali, does not turn red. Hypo-
xanthine does not give Weidel’s reaction. After the action of hydro-
chloric acid and zinc upon a hypoxanthine solution, followed by the
addition of an excess of alkali a ruby-red color develops, followed by
a brownish-red color (Kossel). According to E. Fischer 1
a red
coloration occurs even in the acid solution.
N—C.NH2
Adenine, CsHsNs^HC C—NH\ (6-aminopurine), was first found
II II
>CH
N—C— N ^
by Kossel 2 in the pancreas. It occurs in all nucleated cells, but in
greatest quantities in the sperm of the carp and in the thymus. Adenine
has also been found in lucsemic urine (Stadthagen 3
) . It may be obtained
in large quantities from tea-leaves.
Adenine crystallizes with 3 molecules of water of crystallization in
long needles which gradually become opaque in the air, but much more
rapidly when warmed. If the crystals are warmed slowly with a quan-
tity of water insufficient for solution, they suddenly become cloudy at
53° C, a characteristic reaction for adenine. It dissolves in 1086 parts
cold water, but is easily soluble in warm. It is insoluble in ether, but
somewhat soluble in hot alcohol and easily so in acids and alkalies. It
is more easily soluble in ammonia solution than guanine, but less soluble
than hypoxanthine. The silver compound of adenine is soluble with
difficulty in warm nitric acid, and deposits on cooling as a crystalline
mixture of adenine silver nitrates. With picric acid adenine forms a
compound, CsHsNs.Ce^CNC^sOH, which is very insoluble but
separates more readily than the hypoxanthine picrate, and can be
used in the quantitative estimation of adenine. We also have an adenine
mercury-picrate. Metaphosphoric acid with adenine gives a precipitate
which dissolves in an excess of the acid if the solution is not too dilute.
Adenine hydrochloride gives with gold chloride a double compound
1
Kossel, Zeitschr. f. physiol. Chem., 12, 252; E. Fischer, 1. c.
2
See Zeitschr. f . physiol. Chem., 10 and 12.
» Virchow’s Arch., 109.
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