26 



acetate may be boiled with litharge for ten minutes, the filtrate 

 will be basic lead acetate. ) 



61. Cellulose. (CjHjijOjn occurs in every tissue of the 

 hig-her plants, where it forms the walls of cells and the great 

 mass of hard parts of wood. It is also found in the outer 

 investment of the animals known as Tunicates. Purified 

 absorbent cotton and filter paper are good examples of cellu- 

 lose. Cellulose is insoluble in the ordinary solvents, but can 

 be dissolved in the strong mineral acids, being converted into 

 dextrin. Iodine does not stain the unaltered cellulose, but 

 does so after it has been acted upon by the acid. 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 converted into glucose. 



62. Immerse a piece of filter paper or absorbent cotton 

 in a 1% solution of potassium iodide. lyet dry. Immerse for 

 an instant in sulphuric acid and then immediately rinse in 

 water. If cellulose is present a blue color will appear. 



63. Schulze's reagent. Iodine dissolved to saturation in 

 a zinc chloride solution of specific gravity 1.8 to which 6 parts 

 of potassium iodide has been added, will turn cellulose blue. 



64. Immerse a strip of filter paper for a moment in con- 

 centrated sulphuric acid. Then rinse it immediately in 

 plenty of cold water. If the time of immersion has been cor- 

 rect, the paper will be semi-transparent after washing, and 

 as tough as an animal membrane. It is called vegetable 

 parchment and can be stained blue by iodine. 



IV 



65. Dextrose or Glucose (Grape sugar) (CgHi^Oj) exists in 

 fruits and in small quantities in the blood and other fluids 

 and organs. It is the form of sugar found in diabetic urine. 

 It is readily soluble in water. Use 100 cc. of a 2% solution. 

 Dextrose is made commercially by boiling starch with a dilute 

 acid. 



66. To a portion of this solution add a little iodine solu- 

 tion. Compare with starch. 



