PROPERTIES OF CREATININE. 695 



and VOEGTLIN. The dogs, after feeding with creatine and creatinine, 

 behaved like normal dogs, and the observations of other investigators 

 such as LONDON and BOLJARSKI, 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, shining 

 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 

 cold 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-iHyNsO^ZnC^, is 

 of special interest. This combination is obtained when a sufficiently 

 concentrated solution of creatinine in alcohol is treated with 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- 



l Towles and Voegtlin, 1. c.; London and Boljarski, Zeitschr. f. physiol. Chem., 

 62; Foster and Fischer, Journ. of biol. Chem., 9. 



2 See Huppert-Neubauer, 10. Aufl., and Hoppe-Seyler-Thierfelder's Handbuch. 

 8. Aufl. 



3 Kerner, Pfliiger's Arch., 2; Hofmeister, Zeitschr. f. physiol. Chem., 5. 



