10 THE CARBOHYDRATES. 



If the dry powder is desired, wash with alcohol, then with ether, 

 and dry in a desiccator. 



Prepare glycogen from the liver of a freshly-killed, well-nour- 

 ished animal. The animal is best killed while digestion is in 

 progress. If a rabbit, this may be an hour after introducing 10 to 

 15 grammes of sugar into the stomach through a tube. Remove 

 the liver as soon as posssible, cut it into lumps, and immediately 

 put it into about four times its weight of boiling water. Let it 

 boil half an hour, then rub up the lumps as much as possible in a 

 large mortar, add water, and boil again. Filter through muslin, 

 concentrate upon the water-bath to about one-fourth its volume, 

 and allow the solution to cool. Then precipitate the gelatin and 

 other protein compounds by adding alternately small quantities of 

 hydrochloric acid and potassio-mercuric iodid 1 as long as anything 

 is thrown down. Filter and add to the filtrate twice its volume of 

 alcohol to precipitate the glycogen. Wash with alcohol. To purify 

 the substance it should be dissolved in a little water and precipi- 

 tated again with alcohol. If the anhydrous powder is desired, the 

 water must be removed as far as possible before drying. To accom- 

 plish this wash the precipitate next with absolute alcohol, then 

 with ether to remove the alcohol. Dry in a vacuum-desiccator over 

 sulphuric acid. If the pure substance is not desired, the tests may 

 be made on the solution after the removal of the protein com- 

 pounds. 



1.6. If the dry substance has been obtained, try its 

 taste and its solubility in water. Test the solution with 

 iodin. It gives a red color. 



17. Try Trommer's test (Experiment 9). There is 

 no red color if the glycogen has been purified. If it has 

 not been it contains glucose, which responds to the test. 



18. Convert one portion of the solution into glucose 

 by heating with hydrochloic acid and another by the action 

 of saliva. Test each for the glucose by Trommer's test. 



19. Prove that the glycogen is destroyed (changed 



Prepare by precipitating mercuric chlorid with potassium 

 iodid, washing the precipitate and then adding it to a hot solu- 

 tion of potassium iodid as long as it dissolves. 



