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PROPERTIES OF CREATININE. 895
and Voegtlin. The dogB, after feeding with creatine and creatinine,
I ehaved like normal d< gs, and the observations of other investigators
such as London and Boljabski, Foster and Fisher 1
upon dogs with
Eck fistula have not had any unanimous results or they are hard to explain.
Properties of Creatinine. Creatinine crystallizes in colorless, Bhinin;
monoclinic prisms which differ from creatine crystals in not becoming
white with loss of water when heated to 100° C. It dissolves in 11 parts
cjld water, but more easily in warm water. It is difficultly soluble in
cold alcohol, but the reports in regard to its solubility differ widely.2
It is more soluble in warm alcohol and nearly insoluble in ether. In
alkaline solution creatinine is very easily converted into creatine on
warming.
Creatinine gives an easily soluble crystalline compound with hydro-
chloric acid. A solution of creatinine acidified with mineral acids gives
crystalline precipitates with phosphotungstic and phosphomolybdic
acids even in very dilute solutions (1:10000), (Kerner, Hofmeister 3
).
It is precipitated, like urea, by mercuric-nitrate solution and also by
mercuric chloride. On treating a dilute creatinine solution with sodium
acetate and then with mercuric chloride a precipitate of glassy globules
having the composition 4(C4H7N30.HCl.HgO)3HgCl2 separates on
standing some time (Johnson). Among the compounds of creatinine,
that with zinc chloride, creatinine-zinc chloride, (C^H^NsO^ZnClo. is
of special interest. This combination is obtained when a sufficiently
concentrated solution of creatinine in alcohol is treated wr
ith a concentrated,
faintly acid solution of zinc chloride. Free mineral acids dissolve the com-
pound, hence they must not be present; this, however, may be prevented
by an addition of sodium acetate. In the impure state, as from urine,
creatinine-zinc chloride forms a sandy, yellowish powder which under
the microscope appears as fine needles, forming concentric groups,
mostly complete rosettes or yellow balls or tufts, or grouped as brushes.
On slowly crystallizing or when very pure, more sharply defined prismatic
crystals are obtained. The compound is slightly soluble in water.
Creatinine acts as a reducing agent. Mercuric oxide is reduced to
metallic mercury, and oxalic acid and methylguanidine (methyluramine)
are formed. Creatinine also reduces cupric hydroxide in alkaline solution,
forming a colorless soluble compound, and only after continued boiling
with an excess of copper salt is free suboxide of copper formed. Creat-
1
Towles and Voegtlin, 1. c; London and Boljarski, Zeitschr. f. physiol. Chem.,
62; Foster and Fischer, Journ. of biol. Chem., 9.
2
See Huppert-Xeubauer, 10. Aufl., and Hoppe-Sevler-Thierfelder’s Handbuch.
8. Aufl.
3
Kerner, Pfliiger’s Arch., 8; Hofmeister, Zeitschr. f. physiol. Chem., o.
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