METHODS OF ANALYSIS. 41 



rived from the nuclei of the cells, and, consequently, in an extract 

 that is prepared from fresh, unaltered beef a certain amount of these 

 bodies should be obtained together with the salts and other extractive 

 matter. The determination of the xanthin bases is, therefore, of 

 value in determining the origin of an alleged extract of meat. 



The xanthin base figures in the tables show a variety of results, 

 which is explained by the fact that in the preparation of the extract 

 under certain conditions of heat and pressure some of these bodies 

 are destroyed. The following modification of Schittenhelm's method 

 was employed for their determination: 



Use an amount of the standard solution equivalent to 5 grams of the original extract.' 

 Place in a large evaporating dish and add 500 cc of 1 per cent sulphuric acid. Evap- 

 orate to 100 cc within 4 to 5 hours. Cool and neutralize with sodium hydroxid. 

 Add 10 cc of 15 per cent sodium bisulphate, and 15 cc of 20 per cent copper sulphate; 

 allow this to stand over night, filter, and wash. The precipitate suspended in water 

 is treated with sodium sulphid and warmed on the steam bath. Add acetic acid to 

 acidify and filter hot. To the filtrate add 10 cc of 10 per cent hydrochloric acid and 

 evaporate to a volume of about 10 cc. Filter, make ammoniacal, and add ammo- 

 niacal silver nitrate of 3 per cent strength. After standing several hours the solution 

 is filtered and washed with distilled water until no longer alkaline. The nitrogen 

 in the precipitate is that of the xanthin bases. 



Ammonia. 



Ammonia in meat extracts is determined by the method of the 

 Association of Official Agricultural Chemists, which consists in distill- 

 ing the sample in the presence of magnesium oxid. In several of the 

 samples examined high ammonia results were obtained which might 

 indicate some degree of putrefaction. It is questionable, however, 

 whether the ammonia results obtained by the magnesium oxid 

 method are not too high. 



Many investigators have stated that ammonia salts are present in 

 meat extracts. Probably the ammonia combines with acids of the 

 fatty series to form these salts, which are soluble in alcohol and vola- 

 tile with alcohol vapor. The ammonia is estimated by dissolving 10 

 grams of the meat extract in water, adding barium carbonate and 

 distilling. It has been suggested that ammonium salts, especially 

 ammonium sulphate, are added to meat preparations to increase the 

 nitrogen content, and in some of the extracts examined a relatively 

 high sulphur content was noted. 



SUCCINIC ACID. 



Weidel b first called attention to the presence of succinic acid in meat 

 extracts. Salkowski, c Kutscher and Steudel/ and others claimed 



« IT. S. Dept. Agr., Bureau of Chemistry, Bui. 107, p. 9. 

 bLiebig'sAnnalen, 1871, 158:353. 

 cZts. klin. Med., 1890, Supplement to vol. 17, p. 77. 

 d Zts. physiol. Chem. , 1903, 38 : 101. 



