QUANTITATIVE DETERMINATION OF GLYCOGEN. 245 



best, overnight. Filter through a 15-cm. filter (Munktell) and 

 wash the precipitate with a mixture of one volume of 15 per 

 <jent. potassium hydroxide solution and two volumes of alco- 

 hol (96% Tr.). Collect this wash-fluid in the beaker in 

 which the glycogen was precipitated and pour, it through the 

 filter twice. Then wash the glycogen on the filter with 90 

 per cent, alcohol. 



After the alcohol has drained thoroughly draw a well- 

 cleaned rubber tube over the end of the funnel-tube and 

 close it with a pinch-cock. Under the rubber tube place the 

 empty beaker in which the precipitation of glycogen took 

 place. It makes no difference if a little glycogen sticks to the 

 walls of the beaker. Then fill the funnel full of sterilized but 

 <cold water. After one-half to one hour the glycogen will have 

 .almost completely dissolved. Open the pinch-cock and let 

 the solution run into the beaker. Then close the rubber 

 tube again, pour some more water into the funnel, wait till 

 .all the glycogen has dissolved, and again open the pinch-cock. 

 After the water has run out a second time close the pinch- 

 cock again, fill the filter half full of water, and wash the fine 

 green dust from the paper with the aid of a fine brush. This 

 dust is insoluble in water. Finally allow the wash-water to 

 flow into the beaker. Then place a small piece of litmus 

 paper in the filtrate and let hydrochloric acid, 1.19 specific 

 .gravity, run in from a burette, drop by drop, mixing thor- 

 oughly with a glass rod until the alkali is exactly neutralized. 



Then place a iannel in a 500-cc. measuring-flask and 

 pour in the neutralized glycogen solution with all the neces- 

 sary precautions observed in quantitative analysis. 



Measure out of the burette 25 cc. of hydrochloric acid 

 of 1.19 specific gravity into the beaker and pour this also into 

 the 500-cc. flask. Then place the flask with its funnel under 

 the exit-tube of the funnel which contains the glycogen 

 filter. Fill the beaker with water and pour it on the filter 



