DETERMINATION OF GLYCOGEN. 1401 



water. He employs 400 cc of water, containing 3 to 4 grams of 

 potassium hydroxid, to 100 grams of meat and heat for several hours 

 on a water bath. Any undissolved pieces are then removed with a 

 porcelain spoon, macerated with a pestle, and the heating continued 

 until solution is complete. The time required for the complete solu- 

 tion of the meat may vary from four to eight hours. The solution is 

 then slightly acidified with hydrochloric acid and the proteids pre- 

 cipitated with double iodid of potassium and mercury. In case the 

 last portions of the precipitate do not settle to the bottom, Kiilz 

 obtains a satisfactory clarification by almost neutralizing with alkali 

 and again acidifying with hydrochloric acid. a The proteid precipi- 

 tate is finally separated by filtration, transferred to a porcelain dish 

 containing water to which a few drops of hydrochloric acid and double 

 iodid of mercury and potassium have been added, and the whole 

 stirred and again filtered. Four such washings are found to be suf- 

 ficient. The combined filtrate is treated with twice its volume of 96 

 per cent (W volume) alcohol, allowed to stand twelve hours in a cool 

 place, the supernatant liquid poured or siphoned off, and the glycogen 

 transferred to a filter and washed first with 62 per cent and finally 

 with 96 per cent alcohol. 



From 50 to 60. grams of meat, after having been run through a sau- 

 sage grinder, are treated in an evaporating dish with 300 cc of a 1 per 

 cent potassium hydroxid solution, and heated on the steam bath for 

 about six hours, water being added from time to time so that the vol- 

 ume never becomes less than 150 cc. Finally the water is removed 

 by evaporation until about 150 cc remain. This is made slightly acid 

 with hydrochloric acid (1-5), and hydrochloric acid and double iodid 

 of mercury and potassium added alternately until all proteid matter 

 is precipitated. The hydrochloric acid is added about 2 cc at a time, 

 and the double iodid of mercury and potassium about 10 cc at a time. 

 Usually about 20 to 25 cc are necessary. When the proteid matter 

 separates, and leaves a clear liquid layer above, a small amount 

 of this is carefully poured off and tested by further addition of the 

 reagent. If the precipitation be not complete the liquid is returned, 

 and the proteid precipitant added until the clear liquid above the pro- 

 teid matter gives no precipitate with hydrochloric acid and the double 



a Pfliiger, on the other hand, states that clarification can not be obtained in this 

 way. He finds it necessary to filter, dissolve the precipitate in sodium or potassium 

 hydroxid, acidify with hydrochloric acid, and reprecipitate with Briicke reagent. 

 " b Jour. Am. Chem. Soc., 1900, 22, 85. 



c The double iodid of potassium and mercury is prepared by first precipitating a 

 solution of mercuric chlorid with potassium iodid, washing the precipitated mer- 

 curic iodid till free of chlorids, then saturating a 10 per cent potassium iodid solution 

 with the mercuric iodid at boiling temperature. 



