146 



KREATININ. 



according to the conditions under which the separation takes place 

 and the mode of preparation, and frequently, owing to imperfect 

 development, the crystals assume a very characteristic 'whetstone' 

 form. 



FIG. 10. KEEATININ CRYSTALS. (Krukenberg after Kiihne.) 



Kreatinin is readily soluble in cold water (1 in 11-5) also in alcohol, 

 but is scarcely soluble in ether. The aqueous solutions are usually 

 alkaline, but some observers regard the alkalinity as due to impurities 1 . 

 It acts as a powerful base, forming compounds with acids and salts 

 which crystallise well. Of these the most important is the salt with 

 chloride of zinc (C 4 H 7 N 3 O) 2 ZnCl 2 , both on account of its characteristic 

 crystalline form and of its general insolubility in comparison with the 



FIG. 11. KBEATIN IN- ZINC -CHLORIDE CRYSTALS. (Krukenberg after Kiihne.) 



other compounds of this substance. Hence its formation is employed 

 not merely for the determination of kreatinin but for its separation 



1 Salkowski, Zt. f. physiol. Chem. Bde. iv. (1880), S. 133 ; xn. (1888), S. 211. 



