1 58 SPECIAL PHYSIO L OGY 



(5) Put a bit of absorbent cotton into a beaker or test-tube ; add 

 water; boil; add iodine. Cellulose as represented by cotton fibres 

 does not respond to the iodine test. 



(6) Put a few bits of ash-free filter paper into a test-tube; add 

 water; boil; add iodine. Cellulose as represented by the fibres oi 

 ash-free filter paper is insoluble in water, and responds to the 

 iodine test. One must remember in this connection that in the 

 preparation of ash-free filter paper mineral acids are used to dis- 

 solve out the salts; and mineral acids, especially sulphuric acid, so 

 modify cellulose that it responds to the iodine test with a blue color. 



(7) Add water to dextrine in a beaker; stir with a rod. Dextrine 

 is readily soluble in cold water. To a^ small portion add iodine. 

 The solution will probably assume a wine color; the typical reaction 

 of erythrodextrine. 



(8) Fill a dialyzer with diluted dextrine solution and leave foi 

 subsequent examination. 



(9) Add water to dextrose; it is readily soluble. Add iodine to 

 a portion of the solution; result negative. 



(10) Fehling's Test for a Reducing Sugar. To a few drops of the 

 solution add several cubic centimetres of Fehling's solution and boil. 

 A yellowish precipitate of cuprous oxide (CuO) appears. If the 

 boiling is continued, the color changes to a brick-dust red. 



(11) To a solution of maltose add Fehling's solution and boil; 

 the copper solution is reduced and CuO is precipitated. 



(12) To a solution of lactose add Fehling's solution and boil; 

 reduction takes place. 



(13) Subject a solution of saccharose to the Fehling test. No 

 reduction occurs. Vary the test by boiling the solution with a few 

 drops of dilute HC1 before adding the Fehling solution. The acid 

 splits the disaccharid cane-sugar into its monosaccharid components, 

 one of which reduces the Fehling solution. 



(14) Trommer's Test for a Reducing Sugar. To any liquid suspected 

 of containing a reducing sugar, add a few drops of dilute CuSO 4 

 solution; to this mixture add an excess of NaOH (or KOH); boil; 

 if the suspected liquid contain a reducing sugar the CuSO 4 will be 

 reduced with precipitation of CuO. Subject all of the solutions of 

 sugar in turn to the Trommer test. Note that the appearance is prac- 

 tically the same as with the Fehling test. Any differences are due only 

 to a difference in the proportions of the two reagents. The Fehling 

 test is the more satisfactory one. 



(15) Fill a dialyzer with a dilute solution of dextrose for subsequent 

 examination. 



(16) Fill a dialyzer with a dilute solution of maltose or lactose for 

 subsequent examination. 



(17) Fill a dialyzer with a dilute solution of saccharose for subse- 

 quent examination. 



