CHEMICAL BASIS OF THE ANIMAL BODY. 145 



In the anhydrous form kreatin is white and opaque, but crystallises 

 with one molecule of water in colourless transparent rhombic prisms. 



The crystals are soluble in 75 parts of cold water, extremely soluble 

 in hot; slightly soluble in absolute alcohol, they are more soluble in 

 dilute spirit and are insoluble in ether. The aqueous solutions are 

 neutral in reaction. 



Kreatin is a very weak base, scarcely neutralising the weakest acids, 

 with which it forms soluble crystalline compounds. 



Preparation. Most conveniently from ' Liebig's Extract.' This is 

 dissolved in 20 parts of water and precipitated by a slight excess of 

 basic acetate of lead. The nitrate is then freed from the lead salt by 

 means of sulphuretted hydrogen and concentrated at moderate tem- 

 perature, (avoid boiling) to a thin syrup. On standing in a cool place 

 for two or three days the kreatin crystallises out. The crystals are 

 removed by nitration, washed with 88 p.c. alcohol and purified by 

 recrystallisation from water 1 . 



Kreatin yields no very striking reactions by means of which it can 

 readily be identified. It reduces Fehling's fluid by prolonged boiling 

 without any separation of cuprous oxide. On boiling in presence of 

 alkaline mercuric oxide, a transient red colour is obtained and finally 

 a separation of metallic mercury. The reactions of kreatinin on the 

 other hand are striking (see below), and hence kreatin may be identified 

 with most certainty by conversion into kreatinin, and the determination 

 of the presence of the latter substance. The conversion is readily 

 effected by boiling with dilute mineral acids, during which process 

 kreatin loses one molecule of water : C 4 H 9 lSr 3 O 2 = C 4 H 7 N 3 O + H 2 O. 



Mention has already been made of the possible and very probable 

 genetic relationship of urea to muscle-kreatin (see 484). This is a 

 question to which brief reference will again be made under urea. 



r NH CO -i 



5. Kreatinin. C 4 H 7 N 3 O. NH:C 



X N(CH 3 ).CH 2 J 



Kreatinin as already stated is simply a dehydrated form of kreatin. 

 It occurs normally as a constant constituent of urine, varying however 

 in amount from O5 to 4 '9 grm. per diem according to the amount of 

 proteid food (meat) eaten 2 . It is not a normal constituent of mam- 

 malian muscle but is found in the muscles of some fishes 3 , and has been 

 obtained from sweat 4 . It crystallises in colourless prisms or tables 



1 The mother-liquor from the kreatin may be used for the preparation of 

 hypoxanthin and sarcolactic acid. Drechsel, Darstell. physiol.-chem. Prdparate, 

 1889, S. 29. 



2 Voit, loc. cit. (sub kreatin). 



3 Krukenberg, Unters. physiol. Inst. Heidelb. Bd. iv. Hf. 1. (1881), S. 33. 



4 Capranica, Bull. E. Accad. med. Roma, Ann. vm. (1882), No. 6. 



F. k 



