SEPARATION OF IrROTEID BODIES FROM THE FLESH BASES BY 

 MEANS OF CHLORIN AND BROMIN. 



By H. W. WILEY. 



In dry, finely-ground animal matters from which the fats have been 

 thoroughly extracted witli ether, it is possible to effect an easy separa- 

 tion of the nitrogenous bodies into three groups. These groups, for 

 purposes of dietetic study, are sufficiently distinct to afford a safe basis 

 of valuation of the different nitrogenous constituents. The process 

 which has been adopted in the laboratory of the Division of Chemistry, 

 Department of Agriculture, for this separation is gi^en in detail here. 



DETAILS OF METHOD. 



_n the dry, fat-free, finely-ground animal substance the nitrogenous 

 bodies soluble in water may be separated by first thoroughly exhaust- 

 ing the material with cold or lukewarm water, and afterwards with 

 water near the boiling temperature. By this method the water-soluble 

 constituents of the nitrogenous substances are thoroughly removed. 

 Having determined the total percentage of nitrogen in the whole 

 sample, the residual insoluble nitrogen is determined in the residue left 

 after extraction. This percentage multiplied by 6.25 gives the total 

 quantity of insoluble proteid matter contained in the animal material. 

 In the filtrate the soluble proteid matter which has been dissolved by 

 the water may be completely thrown out of solution by treatment with 

 brornin in the manner about to be described. 



About one-gram portions of the dry animal material are washed with 

 ether by decantation, using from 50 to 100 cc of ether for each sample, 

 and decanting the ether through filters which are afterwards used to 

 receive the portion of the sample insoluble in hot water. After allow- 

 ing the ether to evaporate, the samples are treated first with cold and 

 then with hot water, this washing also being by decantation, the total 

 amount of water used being from 300 to 400 cc. The uudissolved resi- 

 dues are brought on to the filter with the last portions of water. The 

 nitrogen in the residues on the filters is determined by the Gunning 

 method. 



The filtrate from the insoluble portions of the meat is received in 

 Kjeldahl flasks and used for the separation of the soluble proteid nitro- 

 gen by bromiu. The filtrate is first acidulated with two or three drops 

 of strong hydrochloric acid and then about 2 cc of liquid bromin are 

 added and the contents of the flask vigorously shaken. If the bromin be 

 all taken up more is added until finally a globule of i cc of liquid bromin 

 is left undissolved and the supernatant liquid is thoroughly saturated 



27 



