BASES OF CHAPTER V. 



Creatine and Creatinine. 



Preparation of creatine for muscle. Liebig mixed minced meat 

 repeatedly with an equal volume of cold water and pressed out. In 

 the extract the protein was coagulated and, after straining, the solu- 

 tion was treated with baryta until no more precipitate occurred. 

 After filtration and concentration creatine crystallised out in the 

 course of a few days. 



It is, however, better to start with commercial meat extract and 

 after dissolving in twenty parts of water, to precipitate peptones, etc., 

 either with basic lead acetate (Mulder and Mouthaan [1869]) or 

 with tannin (Kutscher [1905]). After removal of the excess of lead 

 or of tannin (see p. 117) the filtrate is concentrated to a thin syrup ; 

 on standing creatine crystallises and is then washed with absolute 

 alcohol to remove creatinine and is recrystallised with charcoal ; the 

 creatinine crystallises from the alcoholic washings on the addition of 

 ether. Creatinine, abundantly present in most commercial meat 

 extracts, is also obtained by Kutscher's method as a silver com- 

 pound in the histidine fraction. Here it is accompanied by carnosine, 

 from which it is separated by solution in alcohol, which leaves the 

 carnosine behind. 



Preparation of creatinine. Creatinine is most conveniently obtained 

 from urine by precipitation with picric acid (Folin and Blanck [1910]). 

 To each litre of urine 18 grm. of picric acid, dissolved in 45 c.c. of 

 boiling alcohol, is added. 



The resulting precipitate, mostly of creatinine potassium picrate, 

 is decomposed by grinding with potassium bicarbonate and, after 

 filtration, the solution is slightly acidified, mixed with two volumes 

 of alcohol, decolourised with a little charcoal and treated with concen- 

 trated alcoholic zinc chloride. The crude creatinine zinc chloride, 

 which separates on standing, may be boiled with lead hydroxide, 

 when about equal quantities of creatine and creatinine are obtained ; 

 or it may be dissolved in warm 10 per cent, sulphuric acid, when the 

 addition of acetone causes the separation of pure creatinine zinc 

 sulphate, (C 4 H 7 ON 3 ) 2 H 2 SO, . ZnSO 4 . 8H 2 O. 



157 



