1400 FOODS AND FOOD ADULTERANTS. 



same time a quantitative or qualitative determination of the glycogen 

 may be of value as confirmatory. 



BRAUTIGAM AND EDELMANN'S METHOD. a 



Boil the finely divided meat with four times its weight of water, 

 treat the resulting broth with dilute nitric acid to precipitate proteids, 

 and filter. Now add a small amount of saturated solution of hydriodic 

 acid so that the two liquids remain in distinct layers. In the presence 

 of glycogen a red or violet ring is formed at the plane of contact of 

 the two liquids. It is also suggested that in case extraction by water 

 be found inadequate a solution containing an amount of potassium 

 hydroxid equal to 3 per cent of the weight of the meat may be sub- 

 stituted as solvent. 



COURLAY AND COREMONS' METHOD. b 



This method is a simplification of the preceding. Grind 50 grams 

 of the material as finely as possibl.e and boil with 200 cc of water for 

 from fifteen to thirty minutes. Filter the broth through a moistened 

 filter paper or piece of fine linen. To a portion of the filtrate in a test 

 tube add a few drops of a reagent composed of 2 grams of iodine, 

 4 grams of potassium iodid, and 100 cc of water. In the presence 

 of glycogen a dark brown color is formed, which is dissipated by 

 heat and reappears on cooling. In case starch is present, as indicated 

 by the blue color of the solution, it may be precipitated by 2 volumes 

 of concentrated acetic acid, separated by filtration, ^and the test for 

 glycogen repeated in the filtrate. 



BRUCKE'S METHOD. c 



Although this method has been largely supplanted, it is given here 

 because all methods that have proved at all satisfactory have been, to 

 a large extent, modifications of that proposed by Briicke. 



Extract the glycogen from the meat by boiling with water and sepa- 

 rate from proteids by precipitating the latter by the alternate addition 

 of double iodid of mercury and potassium and a drop or two of hydro- 

 chloric acid. To the filtrate from this precipitate add alcohol until 

 a marked precipitation of glycogen occurs. Allow the mixture to 

 stand until the precipitate has settled to the bottom, separate the gly- 

 cogen by filtration, and wash first with dilute and then with strong 

 alcohol or with a mixture of alcohol and acetic acid, and finally with 

 ether. 



R. Kiilz follows Briicke's method, except that he decomposes the 

 meat with potassium hydroxid in preference to extracting it with 



a Pharm.C.H.1873,U, 557. 



b Ztschr. Nahr. Hyg. Waar., 1896, 10, 173-174. 



c Sitzungsber, Acad. Wissensch., Wien, Bd. 63, II abth., 1871, p. 214. 



