240 THE INCOME OF ENERGY 



The tube will fill with gas. With a bent pipette 

 introduce about 1 c.c. of a solution of sodium 

 hydroxide (sp. gr. 1.12 = 11 per cent). The gas 

 will be absorbed, with formation of sodic carbon- 

 ate, and the liquid will rise in the tube. 



The growth of the yeast plant is accompanied 

 by the production of carbon dioxide. 



3. Keturn to Experiment 1. After the fer- 

 menting liquid has ceased to give off gas, place a 

 stopper with a bent tube in the mouth of the 

 flask and distill the contents of the flask in a 

 water bath. Condense the first fifth of the dis- 

 tillate. Saturate this with sodium carbonate. 

 Eedistill, and condense. 



Test for alcohol by warming the distillate with 

 potassium dichromate and dilute sulphuric acid, 

 whereby the alcohol will be oxidized to aldehyde, 

 with characteristic odor. 



Alcohol is present. 



The production of alcohol by the yeast is the work 

 of the ferment zymase. 1 This body is closely bound 

 to the protoplasm' of the cell, very easily destroyed, not 

 produced in excess, and not secreted free. Only sugars 

 containing three, six, and nine carbon atoms are at- 

 tacked. The saccharobioses must be u inverted " be- 

 fore they can be fermented. Thus, cane sugar must 



1 Buchner : Berichte der deutschen chemischen GeselLschaft, 

 1897, xxx, pp. 117, 1110, 2668. 



