CARBOHYDRATES 221 



not escape and that no air is admitted. The alkali will absorb 

 the C0 2 , and the liquid will rise in the tube. 



The presence of alcohol in the fermented liquid may be shown 

 by neutralizing and distilling. This is most conveniently done 

 with the combined material of the whole class, the distillation 

 being performed by the laboratory attendant. To about 10 c.c of 

 the distilled liquid add 5-6 drops of 10% sodium hydrate (no 

 more). Warm to about 50 C. (This point may be determined 

 by feeling the test tube. Fifty degrees feels hot, but still can 

 be borne by the hand). Add iodine solution drop by drop until 

 the liquid has a faint brown tinge. Allow the tube to stand. 

 Notice odor of iodoform. This is a test for alcohol. 



b. Levulose. (Fructose.) 



Repeat the following tests made on dextrose, using levulose 

 solution. 



i. Solubility. The solubilities of levulose are similar to those 

 of dextrose. The student need not repeat the tests. 



ii. Fehling's Test. 



iii. Phenylhydrazine Test. Dextrose and levulose form the 

 same osazone, so that they cannot be distinguished one from the 

 other by this test. 



iv. Molisch Test. 



v. Optical Activity. The specific rotation of levulose is 93. 

 Determine the amount of levulose in a solution furnished. 



vi. Fermentation. Levulose ferments readily. 



c. Galactose. 



This sugar gives the usual reduction tests and forms an osa- 

 zone. It may be distinguished from dextrose and levulose by 

 the mucic acid test. Lactose also gives this test, as galactose 

 makes up one-half of the lactose molecule. To distinguish be- 

 tween lactose and galactose one may use the Barfoed test, which 

 reacts with lactose only after prolonged boiling. 



i. Mucic Acid Test. To 50 c.c. of galactose solution add 10 

 c.c. concentrated nitric acid and evaporate on the water bath to 



