RESPIRATION AND FERMENTATION 



139 



Or a fermentation, or other anaerobic, chamber may be used. Or the 

 simple arrangement of figure 36 may be used, the gas being sent into lime- 

 water instead of water, where a double proof of its identity is possible. 



Test for Alcohol. The only available one is the iodoform test, with 

 which the student should make himself familiar by application to known 

 amounts of alcohol before using 

 it in the foregoing experiments. 

 To the solution suspected to 

 contain alcohol add enough of 

 a strong solution of iodine in 

 potassium iodide to turn the solu- 

 tion a marked brown; then add 

 enough strong solution of caustic 

 potash to cause disappearance of 

 the brown color, when, if alcohol 

 is present, there will be precip- 

 itated a quantity of light-yellow 

 crystals, beautifully six-sided un- 

 der the microscope; and at the 

 same time there is emitted a 

 characteristic iodoform odor. 



It will be of interest here 

 for the student to renew his 

 acquaintance with the struc- 

 ture and growth of the yeast 

 plant, which he may very 

 readily and profitably do by 

 making a small culture in an 

 open vessel from which he 

 may draw samples, at inter- 

 vals of a few minutes, for 

 microscopic observation. 



The association of res- 

 piration and fermentation 

 must suggest the inquiry 

 whether they show any 

 resemblance in the very 



important feature of energy release. This may very easily be 

 answered by testimony of good thermometers inserted respectively 

 in the fermenting solution and in a control, viz., a solution with- 

 out the yeast, alongside. 



37. — Demonstration apparatus for 

 fermentation; Xi. 



On the left is the glass still, yielding a distillate 

 in the test-tube below, in the center is the 

 fermentation flask, and on the right is the tube 

 of lime-water. 



