274 METHODS OF ANALYSIS [Chap. 



11 COAGULABLE PROTEINS.— TENTATIVE. 



(For uncooked meat only.) 

 Measure 150 cc. of the extract, from 9, into a 250 cc. beaker and evaporate to 40 

 cc. on a steam bath, with occasional stirring. Neutralize to phenolphthalein, then 

 add 1 cc. of N/1 acetic acid and boil gently for 5 minutes. The coagulum should 

 separate out at once, leaving a clear liquid. Filter on quantitative paper, wash 

 the beaker thoroughly 4 times with hot water, taking special care to clean the sides. 

 Finally wash the coagulum on the filter 3 times, dilute the combined filtrate and 

 washings to a definite volume and reserve for the determination of proteoses, pep- 

 tones and gelatin, 12, and creatin, 16. Transfer the coagulum with the paper to a 

 Kjeldahl flask and remove, with concentrated sulphuric acid, any of the material 

 adhering to the beaker, taking the usual 25 cc. of acid in 5 cc. portions for this pur- 

 pose, heating the acid in the beaker on a hot plate and rubbing with a glass rod. 

 Proceed as directed under 8. Multiply the percentage of nitrogen obtained by 6.25 

 to obtain the percentage of coagulable proteins. 



PROTEOSES, PEPTONES AND GELATIN. 



12 Modified Tannin-Salt Method^. — Tentative. 



Transfer a 50 cc. aliquot of the filtrate, obtained in 11, to a 100 cc. graduated 

 flask, add 15 grams of sodium chlorid and 10 cc. of cold water, shake until the so- 

 diimi chlorid has dissolved and cool to 12°C. Add 30 cc. of 24% tannin solution, 

 cooled to 12°C., fill to the mark with water previously cooled to 12°C., shake and 

 allow the mixture to stand at a temperature of 12°C. for 12 hours or overnight. 

 Filter at 12°C., transfer 50 cc. of the filtrate to a Kjeldahl flask and add a few drops 

 of sulphuric acid. Place the flask in a steam bath, connect with a vacuum pump 

 and evaporate to dryness. Determine nitrogen in the residue as directed in I, 1 8, 

 using 30 cc. of sulphuric acid for the digestion. Conduct a blank determination, 

 using the same amount of reagents, and correct the result accordingly. Mul- 

 tiply the corrected result by 2 and deduct the amount of nitrogen as found from the 

 nitrogen determined in another 50 cc. aliquot of the filtrate from the coagulable 

 proteins without the tannin-salt treatment; the difference multiplied by 6.25 gives 

 the percentage of proteoses, peptones and gelatin. 



13 MEAT BASES.— TENTATIVE. 



Deduct from the percentage of total nitrogen, 8, the sum of the percentages of 

 nitrogen, obtained in the determination of insoluble proteins, 9, coagulable pro- 

 teins, 11, and proteoses, peptones and gelatin, 12, to obtain the percentage of 

 nitrogen of the meat bases. Multiply the result by 3.12 to obtain the percentage of 

 meat bases. 



AMMONIA. 

 Folin Aeration Method^. — Tentative. 



14 APPARATUS. 



Employ the apparatus illustrated in Fig. 9 ; A is a wash bottle one fourth full of 

 10% sulphuric acid; 5 is a tube containing the sample; C is a rubber disc and D is a 

 5 cc. bulb to prevent spray from being carried over into the tube {E) which contains 

 the standard acid; F is a safety bottle. 



DETERMINATION. 



15 



Introduce 2-4 grams of the finely divided meat into the tube {B) and add 20 cc. 

 of ammonia-free water. Place a measured amount of N/25 or N/50 sulphuric or 



