Apr. IS, 1919 Meat Extracts, their Composition and Identification 5 



flask, 50 cc. of a saturated sodium-chlorid solution were added, and the 

 flask filled to the mark with a 24 per cent solution of tannic acid. After 

 a thorough mixing it was placed in the ice box and allowed to stand over- 

 night; any loss in volume due to contraction was corrected by the 

 addition of the tannic-acid solution. On the following day it was filtered, 

 the solution being kept in the ice box during filtration, and 50 cc. of the 

 filtrate, corresponding to 10 cc. of the original, were transferred to a 

 Kjeldahl flask and evaporated to dryness on the steam bath with the 

 aid of a current of air. The nitrogen in the dried residue was determined 

 by the Gunning method and control determinations made on the re- 

 agents used. 



Nitrogen in the tannic-acid-salt precipitate was obtained by subtracting 

 the sum of the tannic-acid-salt filtrate and the coagulable and insoluble 

 nitrogen from the total nitrogen. 



12. "Meat-base" nitrogen. — This was obtained by subtracting 

 the sum of the coagulable, insoluble, ammonia, and tannic-acid-salt 

 precipitate nitrogen from the total nitrogen. 



13. Nitrogen due to peptone-uke bodies. — This was found by 

 deducting the proteose nitrogen obtained by precipitation with zinc 

 sulphate from the total quantity of nitrogen precipitated by the tannic- 

 acid-salt reagent, 



14. NonnitrogEnous organic matter. — This was determined by 

 difference. From the ash-free total solids was deducted the sum of 

 the products of the " meat-base " nitrogen X 3.12 and the nonmeat- 

 base nitrogen X 6.25. 



15. Purins (j). — Three gm. of the sample were dissolved in 500 cc. 

 of a I per cent solution of sulphuric acid and heated for four hours in an 

 open dish on the steam bath. (At the end of this time about 75 cc. should 

 remain.) It was then neutralized with caustic soda, with litmus paper 

 as an indicator, transferred to a beaker, and 15 cc. of a 15 per cent solu- 

 tion of sodium bisulphite and 15 to 20 cc. of a 15 per cent solution of 

 copper-sulphate solution were added. This was allowed to stand over- 

 night, filtered, w^ashed with dilute copper-sulphate solution, and the 

 precipitate then washed with hot water from the paper into the original 

 beaker. The contents of the beaker were brought to the boiling point 

 and sodium sulphid added to precipitate all of the copper. It was then 

 placed upon the steam bath for several minutes, made acid with acetic 

 acid, and allowed to settle thoroughly, after which the precipitate was 

 filtered off, washed with hot water, 10 cc. of 10 per cent hydrochloric 

 acid added to the filtrate washings, and the solution evaporated to dry- 

 ness on the steam bath. Ten cc. more of 10 per cent hydrochloric acid 

 were added and digestion was continued until the bases in the residue 

 were dissolved. It was then filtered, washed, the filtrate made alkaline 

 with 25 cc. of concentrated ammonium hydroxid, 10 cc. of a 3 per cent 



