15 



cubic contiinotoi's of nonual hydnu'liloric acid, uiul tluMi treated with a 

 .slitifht excess of l)romiii while beinj^ vi<^oroiisly shaken. The mixture 

 was allowed to stand twenty-four hours, then filtered, and the precip- 

 itate washed thorou«i-hly with water saturated with hroinin. The nitro- 

 o;on was then deteruiined in the precii)itated proteid. 



Determi nation of nitnnjeti prec'tpltatedhti lnunnln in the jilt rate from, 

 the zinc fodphate jrrecipitate." — The zinc sulphate filtrate was diluted 

 with an equal volume of water and '1 cubic centinu^ters of noiiual 

 hydrochloric acid was added. The precipitation with bromin was 

 coutiuued as in the det«>rmiiiation desciibed above. 



METHODS OF ANALYZING THE BROTHS. 



The methods used in analyzing- tiie l)r<)ths in the experiments here 

 reported are fundamentally the same as those descril)ed in pre\ious 

 bulletins of this Office.'' Nevertheless, as they diti'ei- in some of the 

 details, a l)rief outline of them is here ^iven. U))on removinii- the 

 cooked meat from the vessel in which it was boiled, the hot broth was 

 immediately tiltered throuo-h a sieve with circular openings of 1 milli- 

 meter. The residue in the sicive, consistint>' chiefly of fra<j;nients of 

 meat, was added to the cooked meat. The l)roth was rapidly cooled 

 to about 15^ C. and strained through a piece of cheese cloth previously 

 washed w'ith w^ater, alcohol, and ether. By this means most of the 

 suspended coagulated albumin and nearl}' all of the solidified fat were 

 separated. This coarse residue, after being washed with cold water, 

 was dried and analyzed, first the fat and then the nitrogeii being 

 determined. The tiltered broth was diluted with water to a definite 

 volume and after thorough mixing six portions of 250 cubic centi- 

 meters each were filtered through ash-free filters. In this manner a 

 clear broth w'as obtained. The solid material collected upon the filters 

 was designated as "'fine residues,'' and the ash, nitrogen, and fat in 

 these residues were determined in duplicate. The total solid matter, 

 ash, proteid nitrogen, nonproteid nitrogen, and extractives in the clear 

 filtered broths were determined by the methods described above for the 

 analysis of the cold-water extracts of meats, and in addition, in 

 order to get if possible a further insight into the nature of the nitrog- 

 eneous constitwents present in broths and to study and compare 

 methods for determining these bodies, the following determinations 

 were made: Nitrogenous compounds precipitated by bromin directly; 

 nitrogenous constituents precipitated by tannin and sodium chlorid; 

 compounds of nitrogen precipitated by phosphotungstic acid in the 

 cold; nitrogenous substances precipitated by phosphotungstic acid in 



« This determination has recently been discontinued, as bromin has been proved to 

 be an unreUable precipitant for peptones. 



& U. S. Dept. Agr., Office of Experiment Stations Buls. 102 and 141, 



