110 METHODS OF ANALYSIS. 



casserole with 50 cc of an 8 per cent solution of potassium hydroxid and heat 

 the mixture on the water bath until the meat is entirely dissolved. The 

 operation may be hastened by macerating the larger pieces with a glass rod. 

 Add an equal volume of 95 per cent alcohol, mix thoroughly, filter through an 

 asbestos filter, and wash twice with a hot 4 per cent solution of potassium 

 hydroxid in 50 per cent alcohol. Then wash with 50 per cent alcohol until 

 a small portion of the filtrate does not become turbid upon the addition of acid. 

 Return the precipitate and filter to the original vessel and dissolve, with the 

 aid of heat, in 60 cc of a normal solution of potassium hydroxid. In the case 

 of sausage with a high starch content a somewhat larger volume of alkali may 

 be required. Acidify the filtrate strongly with acetic acid, dilute to a definite 

 volume, thoroughly mix by shaking, filter through a folded filter, and precipitate 

 the starch from an aliquot of the filtrate by means of an equal volume of 95 

 per cent alcohol. Transfer the precipitate to a filter, thoroughly wash with 50 

 per cent alcohol, with absolute alcohol, and finally with ether, dry to a con- 

 stant weight at the temperature of boiling water, and weigh. 



9. Glycogen. 



The determination of glycogen a has been suggested as a means of detecting 

 the presence of horse meat. Subsequent results indicate that this determination 

 is of limited value because of the fact that glycogen begins to disappear soon 

 after the death of the animal, and may entirely disappear after a short lapse 

 of time. No definite conclusions can therefore be derived from the results of 

 this determination, but it is of value as a confirmatory test. 



(a) QUALITATIVE METHOD. & PROVISIONAL. 



Boil 50 grams of the macerated sample with 50 cc of water for from fifteen 

 to thirty minutes. Filter the broth through moistened filter paper or fine linen. 

 To a portion of the filtrate in a test tube add a few drops of a mixture of 2 

 parts iodin, 4 parts potassium iodid, and 100 parts water. In the presence of a 

 large percentage of horse meat the glycogen contained produces a dark-brown 

 color, which is destroyed by heating and reappears on cooling. When starch is 

 present it may be precipitated by two volumes of glacial acetic acid, separated 

 by filtration, and the test for glycogen repeated in the filtrate. 



(b) QUANTITATIVE METHODS PROVISIONAL. 



Digest 50 grams of finely macerated meat on the water bath with 200 cc of 2 

 per cent potassium hydroxid until solution is practically complete. Cool, 

 dilute with water to exactly 200 cc, shake, and filter. Treat 100 cc of the 

 filtrate with 10 grams of potassium iodid ajid 1 gram of potassium hydroxid 

 and stir until solution is complete. Add 50 cc of 96 per cent alcohol and allow 

 to stand until the following day. Separate the precipitated glycogen by filtra- 

 tion and wash with a solution containing 1 cc of 73 per cent potassium hy- 

 droxid, 10 grams of potassium iodid, 100 cc of water, and 50 cc of 96 per cent 

 alcohol. Wash the glycogen with a mixture of two volumes of 96 per cent 

 alcohol and one volume of water (the mixture containing about 7 mg of 

 sodium chlorld per liter), dissolve in water, and remove the remaining traces 

 of proteids by the addition of double iodid of mercury and potassium. It is 



" Niebel, Abs. Zts. angew. Chem., 1895, 620. 



6 Courlay and ('r.-iiuuis. Ahs. Zts. Nulir. Waar.. 1896, 10: IT.'J. 



'Pflttger und Nerking, Arch, gesam. Physiol., 1899, 76: 531. 



