CHAPTER IV 



FERMENTATION AND ALCOHOL 



49. Production of alcohol and vinegar. Unless great 

 care is taken to preserve it, a weak solution of sugar soon 

 turns to vinegar ; a stronger solution 

 turns to alcohol, while a thick, sirupy 

 solution remains unchanged. Every- 

 where there are scattered minute living 

 germs which, falling into a moderately 

 strong solution of sugar in water, grow 

 and produce oval plants each about 

 f$-Q-Q inch in length. A collection of 

 these plants is called yeast. By their 

 growth and multiplication they change 

 sugar to alcohol and carbonic acid gas. 

 The gas bubbles up through the 

 liquid and makes a froth upon the top, 

 while the alcohol remains in the water. 

 If only a small quantity of sugar is present another kind 

 of germ from the air enters and grows, becoming tiny 

 rodlike plants, each about y o 00 inch in length. By 

 their growth and multiplication they change the alcohol 

 to vinegar. They collect in a mass called the mother of 

 vinegar. 



Boiling destroys both the yeast and vinegar germs. If 

 the sugar and water are boiled and at once sealed tightly, 

 so that new germs cannot enter, the solution will keep 



41 



Yeast plant cells (X 500). 



