15 



43- Dextrin. (C^HjoOj) is an intermediate product in the 

 hydration of starch. 



44. Dissolve some dextrin in boiling water and cool. Add 

 iodine solution — a reddish brown color, which disappears on 

 heating and returns on cooling. (The student should take 

 two test tubes placing the dextrin solution in one, and an 

 equal volume of water in the other. Add to both an equal 

 volume of iodine solution and thus compare the difference in 

 color. ) 



45. Cellulose (CjHjuOj) n occurs in every tissue of the 

 higher 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 is a good example of cellulose. 



46. Add some strong sulphuric acid to a little absorbent 

 cotton in a test tube. Note any change and then add a drop 

 of iodine solution. 



V. 



47. Glucose or Dextrose (Grape sugar) (C^Hj^Og) 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. Prepare loo cc. of a 2^ 

 solution. 



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

 tion. Compare with starch. 



49. Heat another portion of the solution with sulphuric 

 acid ; — it darkens slowly. 



50. Trommer's test. To another part of the solution add 

 a few drops of a dilute solution of copper sulphate, and 

 afterwards add caustic potash in excess, that is, until the 

 precipitate first formed is re-dissolved and a clear blue fluid 

 is obtained. The hydrated oxide of copper precipitated 

 from the copper sulphate is held in solution in presence of 



