CH. XII.] CREATININE. 299 



exception being hepatic carcinoma, in which condition the 

 urinary-creatinine is increased and is accompanied by 

 creatine. Creatine is excreted when the muscles of the body 

 are broken down. This explains the presence of creatine 

 in urine during starvation and in fevers. 



When creatinine is given by the mouth it is mainly 

 excreted unchanged, but a small portion is broken down 

 into unknown products. When creatine is administered 

 it also is chiefly excreted unchanged, but a certain per- 

 centage is destroyed in the body. The amount excreted 

 unchanged is considerably increased with diets rich in 

 proteins. 



Properties. Creatinine dissolves in 1 1 parts of water 

 and 1 02 parts of alcohol at 16 C. It is insoluble in ether. 

 Its solutions are neutral or very slightly alkaline in reaction. 



Creatinine is precipitated by phosphotungstic acid, by 

 picric acid, and by the salts of the heavy metals. It forms 

 a characteristic compound with zinc chloride, which is used 

 for the preparation of standard solutions. 



Alkalies convert it slowly into creatine. On boiling 

 with barium hydroxide it is converted into urea and 

 sarcosine (see p. 178). 



Creatinine reduces Fehling's solution, but not Bene- 

 dict's or Ny lander's solutions. 



Creatine is converted to creatinine by heating with 

 acids (see Ex. 226). It can be estimated by making 

 determinations of creatinine before and after heating the 

 urine with acid. If aceto-acetic acid is present Graham 

 has found that both results are liable to considerable error 

 (see Graham and Poulton, Proc. Roy. Soc., LXXXVII., B., 

 p. 205). For the method of estimation see p. 336. 



362. Preparation of Creatinine from urine.* 



(i.) Preparation of creatinine pier ate. 



It is best to work on 10 litres of urine at least. Dissolve 40 grams, of picric 

 acid in 100 cc. of boiling alcohol and use 1 8 grams, of picric acid per litre of urine. 

 Pour the hot solution directly into the urine, stirring well during the addition. 



* (Benedict, Journal of Biological Chemistry, xviii., p. 183.) 



