CH. VII.] MEAT. 179 



lead sulphide. Evaporate the filtrate, filtering off any sulphur or 

 sulphide that may be deposited. Continue the evaporation till a 

 syrup is obtained. Allow this to stand in the ice chest for two or 

 three days. Creatine separates out, mostly as oblique rhombic 

 crystals. Examine a few under the microscope. Treat the syrup 

 with 200 cc. of 88 per cent, alcohol, stir thoroughly with a glass 

 rod and filter through a small paper. The creatine remains on the 

 paper, the alcoholic filtrate containing the purine bases. 



NOTE. Many specimens of commercial meat extract contain creatinine 

 as well as creatine. Rabbit's muscle is the best source of pure creatine. The 

 muscle is finely minced, extracted with boiling water, the proteins removed 

 by boiling and adjusting the reaction. The filtrate is worked up as described 

 above. 



226. Conversion of creatine into creatinine. Dissolve the 

 creatine in about 30 cc. of hot water and divide the solution into two 

 equal portions, A and B. Treat B with an equal volume of normal 

 HC1 and heat on a boiling water bath in a flask fitted with a cork 

 and long glass tube (to act as an air condenser) for three to five hours. 

 The creatine is converted into creatinine. Neutralise the solution 

 with caustic soda. 



Test A and B for creatinine by the following tests: 



227. Jaffe's test for creatinine. Treat 10 cc. of the solution 

 with 15 cc. of saturated picric acid solution and 5 cc. of 10 per 

 cent, caustic soda. Allow the mixture to stand for 5 minutes and 

 dilute to 200 cc. A deep orange colour appears in B due to the 

 formation of picramic acid from creatinine. The creatine in A gives 

 no colour. 



228. Weyl's test for creatinine. Treat 5 cc. with a few drops 

 of a freshly prepared sodium nitroprusside and make the solution 

 just alkaline with sodium hydroxide. A ruby-red colour appears. 

 Boil. The solution turns yellow. Acidify with an excess of 

 acetic acid and heat. A green tint appears, and a blue deposit of 

 Prussian blue may result on standing. 



Purine bases. These compounds are interesting because 

 of their chemical relationship to uric acid. This relation- 

 ship is shewn by the formulae given on p. 62. 



