DETERMINATION OF REDUCING SUGAR AND NITRATES. 1403 



The glycogen is once more precipitated by means of 2 volumes of 

 96 per cent (by volume) alcohol, filtered, washed with 96 per cent 

 alcohol containing a small amount of salt, then with absolute alcohol, 

 finally with ether, dried to constant weight, and weighed. 



As a control the precipitated glycogen is hydrolized by boiling with 

 a 2.2 per cent solution of hydrochloric acid and the reducing sugar 

 determined. . 



Satisfactory results have been obtained by the writer by hydrolizing 

 with hydrochloric acid the precipitate obtained with potassium iodid 

 and alcohol from the potassium hydroxid solution of the proteids 

 without further purification. 



DETERMINATION OF REDUCING SUGAR. 



Boil 100 grams of the finely divided meat for fifteen or twenty min- 

 utes in a 500 cc graduated flask with a convenient volume (200 or 300 cc) 

 of water. Add a few cubic centimeters of a saturated solution of normal 

 lead acetate solution, cool to room temperature, make up to the mark 

 with water, and filter through a fluted filter. Evaporate to a small 

 volume as large an aliquot portion of the filtrate as practicable, add a 

 saturated solution of sodium sulphate, make up to a definite volume, 

 and filter through a fluted filter. Determine reducing sugar in an 

 aliquot portion of the filtrate by the Allihn method. The percentage 

 of reducing sugar thus found is multiplied by 0.9 and the result added 

 to the percentage of glycogen. 



DETERMINATION OF NITRATES. 



Saltpeter is usually used in the preparation of corned meat and of 

 meat that is cured for smoking. Potted meats and similar preparations 

 often contain relatively large amounts of cured and smoked meat. 



QUALITATIVE DETECTION OF NITRATES. 



One or two grams of the meat are treated in a porcelain dish with 

 2 or 3 cc of a 1 per cent solution of diphenylamin in strong sulphuric 

 acid. In presence of even a minute trace of nitrate, a deep blue color 

 is formed instantly, and may be readily seen in spite of the charring 

 produced by the sulphuric acid. 



METHOD OF SCHLOSING-WAGNER. a 



A flask (fig. 1) of about 250 cc capacity is provided with a rubber 

 stopper with two holes. Through one of them is passed the stem 

 of a funnel carrying a glass stopcock. The other carries a delivery 

 tube leading to the receiving vessel. The end of the delivery tube is 



a Agr. Chem. Vers. Stat. Halle, p. 50; Wiley, Principles and Practice of Agricul- 

 tural Analysis, vol. 2, p. 228. 



