QUANTITATIVE DETERMINATION OF GLYCOGEN. 247 



500-cc. flask. The glucose in this solution is then determined 

 gravimetrically (see Determination of Glucose, page 200). 



According to Salkowski * it is much better not to treat 

 the fresh liver with caustic potash solution, but to subject 

 it to a preliminary treatment with alcohol and ether. This 

 is done by extracting the finely chopped liver with absolute 

 alcohol and then with ether, thus converting it into a fine 

 powder. This dissolves comparatively readily in 2-3 per 

 cent, potassium hydroxide solution, the rapidity of the solu- 

 tion depending upon the completeness of the pulverization 

 of the liver. If this has been well done, then the solution in 

 the caustic potash takes place in a few minutes. The solu- 

 tion is brown-colored and not quite clear owing to the pres- 

 ence of undissolved calcium phosphate. Only compara- 

 tively small quantities of the liver powder, 5 to 10 g., need 

 to be taken for the glycogen determination. 



The alkaline solution is clarified by letting it stand it is 

 advisable to take only an aliquot part, in order to avoid, 

 filtering, about four-fifths and then it is precipitated with 

 double its volume of alcohol, the precipitate washed, first with 

 66 per cent, alcohol, then with stronger alcohol, and dried at 

 105. The glycogen thus obtained contains only a trace of 

 nitrogen, though it leaves considerable ash when ignited. 

 It may be determined as glucose after hydrolyzing according 

 to Pfluger's method given above. 



The liver powder, prepared as stated above, also dis- 

 solves very quickly in artificial gastric juice. With 5 g. of 

 the powder Salkowski found no glycogen in the residue left 

 after digesting for forty-six hours, nor did the coagulum 

 resulting from boiling the solution, after it had been nearly 

 neutralized, contain even a trace of glycogen. From the 

 filtrate, after evaporating it to about 150 cc., the addition 



1 Zeit. f. physiologische Chemie, 36, 257. 



