12 THE CARBOHYDRATES. 



Cellulose is only slightly attacked by the digestive ferments 

 of man, though the herbivorous animals digest it to a 

 greater extent. By the continued action of acids it is con- 

 verted into glucose. 



21. Show that cellulose is not stained by iodin. Use 

 absorbent cotton or starch-free filter paper. 



_22.-=Try the solubility of cotton or filter-paper in solution of 

 zinc chlorid (Schultze's reagent) and also in a solution of cupric 

 hydrate in ammonium hydrate (Schweitzer^s reagent). It can be 

 precipitated from these solutions by dilution with water. 



23. To one volume of water in a beaker add slowly 

 two volumes of concentrated sulphuric acid, stirring mean- 

 while. Cool the mixture; then immerse in it for a few 

 seconds a piece of heavy filter-paper, plunging it into a 

 large beaker of cold water as soon as it is removed. If the 

 time of immersion has been correct it will be semi-trans- 

 parent after washing, and as tough as an animal mem- 

 brane. It is called vegetable parchment. It can be stained 

 blue by iodin. 



24. Let another piece of paper remain in a small 

 amount of the warm acid until it has entirely disappeared. 

 Then dilute a little of the acid with water and test it for 

 glucose by Trommer's test (Experiment 9), being sure that 

 enough alkali has been added to give it an alkaline reac- 

 tion. 



GLUCOSE (C 6 H 12 6 ). 



Glucose is also called dextrose and grape-sugar. It is 

 found in the vegetable kingdom as well as in the animal. 

 It is normally present in the blood and lymph and in other 

 fluids of the body. Pathologically it is found in consider- 

 able quantities in the urine, sometimes in as large amounts 

 as 10 per cent, or more. The urine may also temporarily 



