1248 CREATINE. 



conversions of creatine and creatinine. This is the cause of 

 the conflicting statements as to the occurrence of creatine in 

 urine ; as a matter of fact this excretion always contains crea- 

 tinine. It is on the whole most probable that any creatine which 

 may be found in urine is due to the conversion of creatinine into 

 creatine during its extraction, since it has been shewn that the 

 more rapidly the separation is effected, the less is the quantity 

 of creatine obtained, and the greater the amount of creatinine. 



In the anhydrous form creatine is white and opaque, but 

 crystallizes with one molecule of water in colourless trans- 

 parent 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. 



Creatine is a very weak base, scarcely neutralizing the weak- 

 est 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 filtrate is then freed from the lead salt 

 by means of sulphuretted hydrogen and concentrated at moderate 

 temperature (avoid boiling) to a thin syrup. On standing in a cool 

 place for two or three da}^s the creatine crystallizes out. The crys- 

 tals are removed by filtration, washed with 88 p.c. alcohol and puri- 

 fied by recrystallization from water. 



Creatine yields no very striking reactions by means of which 

 it can readily be identified. It reduces Fehling's fluid by pro- 

 longed 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 creatinine on the other hand are striking (see 

 belcw), and hence creatine may be identified with most cer- 

 tainty by conversion into creatinine, and the determination of 

 the presence of the latter substance. The conversion is readily 

 effected by boiling with dilute mineral acids, during which pro- 

 cess creatine loses one molecule of water : C 4 H 9 N 3 2 = C 4 H 7 N 3 

 + H 2 0. 



Mention has already been made of the possible and very 

 probable genetic relationship of urea to muscle-creatine (see 

 § 382). 



, NH CO -, 



11. Creatinine. C 4 H 7 N 3 0. 



NH:C( 



N(CH 3 ).CH 2 J 



Creatinine as already stated is simply a dehydrated form of 

 creatine. It occurs normally as a constant constituent of urine, 

 varying however in amount from 0-5 to 4*9 grm. per diem 

 according to the amount of proteid food (meat) eaten. It is 



