178 THE CHEMISTRY OF SOME FOODS. [CH. VII. 



224. Dissolve in a little ammonium sulphate and take the 

 temperature at which the myosin coagulates. It coagulates at 

 about 57 C. (see Ex. 218). 



Creatine. This is the most abundant nitrogenous 

 extractive in muscle, being present to the extent of about 

 0*4 per cent. Chemically it is methyl-guanidine-acetic 

 acid. 



NH CH 3 



II I 

 C N CH 2 



NH 2 COOH 



On hydrolysis with baryta water it is converted into 

 urea and sarcosine (methyl glycine). 



NH CH 3 NH 2 CH 3 



II I I 



NH 2 .C N.CH 2 .COOH+H 2 = NH 2 .CO + NH.CH 2 .COOH. 



Urea. Sacrosine. 



On being boiled with mineral acids it is dehydrated 

 to creatinine. 



NH CH 3 



II I 

 C N CH 2 



NH- -CO 



Creatinine is found in normal human urine, but 

 creatine only under abnormal conditions. 



225. Separation of creatine from meat extract. Dissolve 

 10 grams, of commercial meat extract in 200 cc. of water. Add 

 slowly a saturated solution of lead acetate till no further precipitate 

 is formed, carefully avoiding an excess. This is best done by 

 filtering samples and testing them with lead acetate. Filter off the 

 precipitate of proteins and phosphates. Warm the nitrate and 

 decompose the soluble lead compounds by means of a stream of 

 sulphuretted hydrogen. Warm and filter off the precipitate of 



