258 PHYSIOLOGICAL CHEMISTRY 



Gently rub up the yeast with the sugar solution to be tested, 

 making a homogeneous mixture. 



Fill an Einhorn fermentation tube with this mixture. Make 

 sure that all air is removed from the tube. When the tube is 

 full, pour out most of the liquid from the bulb. Otherwise it will 

 overflow into the incubator in case fermentation takes place. 

 Label the tube with your name and the kind of sugar under ex- 

 amination and place in an incubator at 38-40 C. until the next 

 class period. Remove the tube and add 3-4 c.c. cone, sodium 

 hydrate from a pipette in such a way that it will enter the upright 

 portion of the tube. Be careful that the gas in the tube does 

 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. 



Levulose. (Fructose. ) 



Repeat the following tests made on dextrose, using levulose 

 solution. 



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

 of dextrose. The student need not repeat the tests. 



10. Benedict's Test. 



11. Pkenylhydrazine Test. Dextrose and levulose form the 

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

 other by this test. 



12. Molisch Test. 



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

 Determine the amount of levulose in a solution furnished. 



14. Fermentation. Levulose ferments readily. 



