STUDY OF YEAST. 95 



1. State in your note-book the color of the 



mixture. Does it appear clear or cloudy ? 



2. What is the smell and taste of the mixture? 



3. Place the liquid where the temperature is 



70 to 90 F. Determine the exact tem- 

 perature by the use of a thermometer, 

 and record it. 



4. At the end of several hours examine the liq- 



uid. What evidence is there that the 

 yeast is ' ' working ' ' ? 



5. At the end of 12 hours smell the mixture of 



molasses and yeast remaining in your 

 large bottle. How does it differ from 

 that observed in 2? 



6. Taste of the liquid at the same time. Com- 



pare with result obtained in 2. 



7. What differences do you note in the color 



or in the general appearance of the mix- 

 ture since the experiment was begun? 

 (Compare with observations in i.) 



8. Determine the effect of temperature on the 



working of yeast in the following man- 

 ner: 



a. Shake up the mixture when it is work- 

 ing well, and pour some off into a 

 small bottle; immerse the latter 

 up to its neck in ice-water for an 

 hour, or place it in a refrigerator. 



(1) What is the effect on the ac- 



tivity previously noticed in 

 the liquid? 



(2) Warm the liquid again to the 



