40 MEAT EXTRACTS. 



Definite amounts of kreatin and kreatinin were added to samples 

 of meat extracts and practically the entire amounts added were 

 recovered by this method. The color of the various extracts inter- 

 fered slightly with the reaction and attempts were made to remove 

 the color by precipitating with basic acetate of lead and phospho- 

 tungstic acid and by filtering through animal charcoal. In all such 

 cases, however, low results were obtained on testing the filtrate for 

 kreatinin. Consequently, in this work the kreatinin method was 

 applied directly to the coagulable proteid filtrate and no allowance 

 was made for the error due to the color. Since the method calls for 

 a dilution to 500 cc and but 10 to 15 cc are used for the determination, 

 this error is negligible. Grindley and Woods" have determined 

 separately the kreatin and kreatinin content of several extracts of 

 meat and found both present in varying amounts. It is necessary, 

 therefore, to determine these two bodies separately when a careful 

 study of the nitrogenous bodies of meat extract is made. Some later 

 experiments in the Bureau of Chemistry have shown that three and 

 one-half hours heating in a boiling water bath is necessary for the 

 complete conversion of kreatin into kreatinin. Benedict and Myers b 

 have described a rapid method for the estimation of kreatin and 

 kreatinin by conversion into kreatinin in an autoclave. This 

 method reduces the time of dehydration of the kreatin to fifteen 

 minutes. 



APPLICATION OF KREATININ TEST TO TANNIN-SALT FILTRATE. 



In view of the fact that a portion of the kreatin in a sample of 

 meat extract is precipitated by the tannin-salt reagent the total 

 kreatin and kreatinin in the filtrate from the tannin-salt precipi- 

 tate is determined, as well as the total kreatinin in the extract, before 

 adding the reagent. A more correct figure is accordingly obtained 

 for the total meat bases by adding to the total meat bases figures the 

 amount of total kreatinin precipitated by the tannin-salt reagent. 

 In applying the Folin method to the filtrate of the tannin-salt pre- 

 cipitate considerable difficulty was encountered. The tannin was 

 removed by means of baryta and the barium with sulphuric acid. 

 After neutralizing, the total kreatinin was determined in the usual 

 manner. In the estimation of the peptones, correction must like- 

 wise be made for the amount of kreatin and kreatinin precipitated 

 by the tannin-salt reagent. 



Xanthin Bases. 



In addition to kreatin and kreatinin, a true meat extract or meat 

 juice should contain small amounts of xanthin bases, including 

 xanthin, hypo-xanthin, guanin, and adenin. These bodies are de- 



a J. Biol. Chem., 1907, 2 : 309. c J. Amer. Chem. Soc, 1906, 28 : 1485. 



&Amer. J. Physiol., 1907, 18:397. 



