17 



acetate. Heat in the water-bath for 20-30 minutes ; then 

 cool the test-tube by allowing cold water to run upon it and 

 set it aside. A yellow crystalline precipitate is formed which 

 is known as phenyl-glucosazone. Examine some of this pre- 

 cipitate under a low power of the microscope and note the 

 needle-like and feathery crystals sometimes arranged in the 

 form of rosettes. Phenyl-glucosazone has a melting point 

 of 204° C. 



54. Conversion of starch into glucose. Boil some of the 

 starch solution with a few drops of sulphuric acid until the 

 fluid becomes clear. After neutralizing a small portion 

 with sodium carbonate, test it for glucose by the iodine test. 



55. Lactose. Milk sugar, (C^HjjO^ and H^O). Make 

 50 cc. of a 2% solution. 



56. Heat a portion of this solution carefully with sul- 

 phuric acid, — it chars slowly. 



57. Add to another portion excess of caustic soda and a 

 few drops of copper sulphate solution and heat, — a yellow 

 or red precipitate (like gluco.se). 



58. Test another portion with Fehling's solution, — there 

 is a reduction like glucose, but its reducing power is not so 

 great as glucose. It requires 10 parts of lactose to reduce 

 the amount of Fehling's solution that will be reduced by 7 

 of glucose. 



59. Cane sugar (Cj^H^jOn). Make 50 cc. of a 2% 

 solution. 



60. A portion of the solution should not reduce Fehling's 

 solution. (Many of the commercial sugars, however, con- 

 tain sufi&cient reducing sugar to do this.) 



61. Trommer's test. Add excess of caustic potash and a 

 drop of copper sulphate (it gives a clear blue fluid), and 

 heat. With a pure sugar there should be no reduction. 



62. Pour strong sulphuric acid on a little dry cane sugar 

 in a test-tube. Add a few drops of water with a pipette, 

 the whole mass is quickly charred. 



