ADVANCED CHEMICAL PHYSIOLOGY 



323 



A similar extract may be prepared by dissolving some commercial 

 meat extract in water. 1 



To remove the phosphates and the last traces of proteins from this 

 extract a saturated solution of subacetate of lead is added to it until no 

 more precipitate is produced. (Care should be taken that an excess 

 of the subacetate solution is not added. This may be ascertained by 

 filtering samples of the extract and seeing if these yield further pre- 

 cipitates with the subacetate solution. ) The precipitate thus obtained 

 is removed by filtration. 



A. 



FIG. 203. Crystals obtained from meat extract, mostly creatine, a few 

 sodium chloride. 



The excess of lead is precipitated from the nitrate by passing a current 

 of sulphuretted hydrogen through it. The precipitate of lead sulphide 

 is removed by filtration. The nitrate is then evaporated to small bulk 



1 The following amounts are suitable for this preparation : 10 gms. bovril 

 or lemco are dissolved in 200 c.c. water, and to this is slowly added 60 c.c. of a 

 saturated solution of subacetate of lead. After the precipitate has settled 

 down a sample of the supernatant fluid is removed by a pipette to a test tube 

 and tested with the subacetate solution to be certain that no more precipitate 

 is produced. 



