MEAT AND MEAT PRODUCTS. 19 



by difference, as suggested by the writer) to a small volume and saturate with zin 

 sulphate. About 85 grams of powdered zinc sulphate are necessary for the saturation 

 of 50 cc of the liquid at ordinary laboratory temperature. The liquid must be fully 

 saturated with the salt, but a large excess should be avoided, as it is likely to cause 

 " bumping" in the subsequent determination of nitrogen in the solution. Letstand 

 several hours, filter, and wash the precipitate with saturated zinc sulphate. In case 

 the precipitate is voluminous, which rafrely happens, the mixture maybe made up to 

 a definite volume with saturated zinc sulphate, filtered, the nitrogen may be deter- 

 mined in an aliquot portion of the filtrate, and the nitrogen of the precipitated 

 proteids determined by difference. 



(g) DETERMINATION OF PEPTONES.* 



Dilute the filtrate from the zinc-sulphate precipitate of proteoses and gelatin with 

 an equal volume of water, add bromin until a globule of from 0.5 cc to 1 cc remains 

 undissolved after the liquid is saturated, and allow to stand over night. Filter, wash 

 with cold water, directing the jet to the globule of bromin so as to keep the wash 

 water saturated. Transfer the filtered precipitate to a Kjeldahl flask and determine 

 nitrogen. 



(h) DETERMINATION OF GELATIN. 



Stutzer's method b modified by Bigelow. 



Boil 10 grams of the sample for a few minutes with water; filter, wash, and evap- 

 orate the filtrate to dryness in a porcelain dish of about 10 cm diameter, after the 

 addition of about 20 grains of sand which has been freed from dust by sifting, and 

 thoroughly ignited. Exhaust the residue with four 100-cc portions of absolute 

 alcohol, and pass the supernatant liquid through an asbestus filter which rests on a 

 porous plate of about 4 cm diameter, in a funnel. The funnel is surrounded by 

 pounded ice and attached to an aspirator, by means of which gentle and gradually 

 increasing suction may be applied. Take care to transfer as little as possible of the 

 insoluble residue to the filter. Then extract the residue repeatedly with 100-cc por- 

 tions of a mixture containing 100 cc of 95 per cent alcohol (sp. gr. 0.81), 300 grams of 

 ice, and 600 grams of cold water, taking care that the temperature shall not exceed 5 C. 

 at any time. Continue the extraction until the various portions of solvent used are 

 entirely colorless. Filter the extract through the funnel employed for the alcohol 

 extract. Finally, return the asbestus filter to the beaker which contains the 

 exhausted residue and thoroughly extract the whole with boiling water. Receive 

 the hot-water extract in a Kjeldahl flask, determine nitrogen, and multiply the 

 percentage of nitrogen so obtained by 5.55 for the percentage of gelatin and gelatin 

 peptone. 



(i) PROTEOSES. 



Deduct the nitrogen in the gelatin precipitate (h) from that of the proteose and 

 gelatin precipitate. This multiplied by 6.25 gives the percentage of proteoses. 



(j) MEAT BASES. 



Deduct from the total nitrogen (a) the sum of the nitrogen in (b), (c), (d), (f), 

 and (g). Multiply trie difference by 3.12 for meat bases. 



6. DETERMINATION OF GLYCOGEN. 

 Proceed as directed on page 13. 



7. DETECTION OF PRESERVATIVES. 

 Proceed as directed under Preservatives, page 107. 



Allen Com. Org. anal, 2nd Ed,, vol. 4, p. 320. 



bZtschr. anal. Chcni.. ISHD. 4, 568. 



U. S. Dcj>t. of A.m., Huivau of Chcm., Bui. 13, Part 10. 



