DIGESTION AND ABSORPTION. 155 



sume a wine color; the typical reaction of erythro dex- 

 trin. 



(8) Fill a dialyzer with diluted dextrin solution and 

 leave for 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 centimeters of Feh- 

 ling's solution and boil. A yellowish precipitate of 

 cuprous oxide (CuO) appears. If the boiling is con- 

 tinued 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 pre- 

 cipitated. 



(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. 



(14) Tromer's test for a reducing sugar: To any liquid 

 suspected of containing a reducing sugar, add a few 

 drops of very dilute CuSO 4 solution; to this mixture, 

 add an excess of NaOH (or KOH); boil; if the sus- 

 pected 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 Tromer test. 

 Note that the appearance is practically the same as 

 with the Fehling test. Any differences are due, not to 

 a difference in the essential reaction but to a difference 

 in the proportions of the two reagents. The Fehling 

 test is more satisfactory. 



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

 subsequent examination. 



