58 ANATOMY AND PHYSIOLOGY 



3. Place a greased glass plate over each cylinder, or 

 close the cylinders with a rubber stopper, and after 

 an interval of about one hour (at a temperature 

 of about 25C.) repeat the tests for O and C0 2 . 

 Test again after two or more hours. 



4. Record and interpret your results, especially dis- 

 cussing any circumstances that may have operated 

 to affect the progress of the experiment either favor- 

 ably or unfavorably. 



C. The Formation of Alcohol Demonstrated: 



Experiment 35. To test for the presence of alcohol. 



1. After the fermentation in the last experiment has 

 proceeded for twenty-four hours, distill about 150 

 to 200 c.c. of the fermenting liquid, and redistill the 

 first distillate. 



2. Test a portion of the second distillate with a flame 

 to see if it will burn. If it will, describe and explain 

 the result. 



3. The presence of alcohol may also be tested, in 

 either the first or the second distillate, by adding to 

 it several drops of a mixture composed of a strong 

 aqueous solution of bichromate of potash, to which 

 have been added a few drops of sulphuric acid. If 

 a green color results, the presence of alcohol is 

 indicated. 



4. Briefly summarize the products of alcoholic fer- 

 mentation, ascertained by the above experiments. 

 From where did these products come, and what 

 was the active agent in their formation? 



