145 



tion with zinc sulphate, was, us a rule, k\ss than ono-teiith of the nitro- 

 gen I'oajiuhitod by heat. Tlie average found in the 11 samples of fresh 

 beef was U.(i280 per cent, and in the 2 samples of veal 0.0388 per cent. 



In a few of the raw meats the nitrogen in the form of peptones was 

 determined ])y treating with bromin the tiltrate from the zinc sulphate 

 prcfipitate. Only a very small amount of precipitate was obtained, 

 the average quantity in the six tests l)eing 0.0085 per cent. It has 

 recently been fully demonstrated" that the use of bromin as a precipi- 

 tant for proteids can not l)e relied upon. 



For the time being we have assumed that the sum of the nitrogen 

 coagulated by heat and that precipitated as albumoscs by zinc sulphate 

 represents the total soluble proteid nitrogen, except that in the cases 

 where bromin has been used as a reagent the nitrogen thus precipitated 

 has also l)een included in the proteid nitrogen. Investigations made 

 in this laboratory lead to the belief that neither of these methods gives 

 entirely trustworthy results, but that for the time being the first is in 

 all probability the better method, notwithstanding the fact that the 

 filtrate from the zinc sulphate precipitate still contains traces of nitro- 

 gen in the form of proteid. While the results thus obtained for the 

 solul^le proteid nitrogen can not be considered linal and conclusive, 

 they undoubtedly approximate the truth, and there is no doubt that by 

 the careful use of these methods comparable results may be obtained. 



The nitrogen of soluble proteid in the uncooked meats analyzed 

 varied from 0.1988 per cent in beef ilank (sample No. 1672) to 0.4520 

 per cent in veal leg (sample No. 1656), the average for the 13 samples 

 of raw beef and veal being 0.3682 per cent. The nitrogen in the form 

 of nonproteid substances is quite similar in amount to the nitrogen of 

 the soluble proteids, and apparently varies directly as the latter. The 

 nonproteid nitrogen varied from 0.1463 to 0.4522 per cent of the 

 ^veight of the rawmeats, the average for the 13 samples of beef and 

 veal being 0.3506 per cent. 



The data obtained indicate that there is a small amount of nitrogen 

 invarial)ly present in the form of ammonia or ammonium salts in cold- 

 water extracts of raw flesh. This has been found to ))e true even where 

 barium carbonate was used to remove the ammonia by distillation. 



As pointed out by C. Mai,* the ratio of ammonia nitrogen to total 

 nitrogen increases after meat has been hung for three or four days. 



It is expected that a discussion of the relative value of bromin, 

 phosphotungstic acid, tannin, and Stutzer's reagent for the estimation 

 and separation of proteid and nonproteid substances will be considered 

 in some detail in another publication from this laboratory, the dis- 



« U. S. Dept. Agr., Bureau of Chemistry Bui. 81, pp. 104, 117, and 228. 

 &Ztschr. Untersuch. Nahr. u. Genussmtl., 4 (1901), No. 1, p. 18. 



11480— No. 162—06 10 



