RESPIRATION— AERATION— FERMENTATION 227 



Place a glass bell jar with an opening at the top in each. Put fresh active 

 green shoots into A and B. Put a burning candle (2 or 3 inches high) 

 supported by corksi under each jar. Pour water into the dishes until it 

 rises 2 or 3 inches. Put corks into the tops of the jars and note the effect 

 on the flames. Explain. Cover jar B with a heavy black cloth and set all 

 three in strong sunlight for three hours. Lower a lighted taper into each 

 and note the effect. Explain. 



Exercise 4. Put 10 per cent, sugar solution of glucose, sucrose, and 

 lactose each into two fermentation tubes as directed by the laboratory 

 instructor. Put a fragment of good yeast into each, plug with cotton and 

 set aside for twenty-four hours. Test those showing gas by inserting a 

 stick of caustic potash. Explain. 



Exercise 5. Pour 500 c.c. of modified Pasteur's * solution into a one- 

 liter Erlenmyer flask; add two grams of good yeast. Close the flask with 

 a cork carrying the short arm of a bent glass tube, the long arm so bent 

 as to reach a wash bottle. Allow the fermentation to drive out the air ■ 

 then insert the long arm into a bottle of baryta water. Note the effect 

 and explain. 



Allow the flask to stand for a week so as to permit complete fermenta- 

 tion. Test a small amount of the liquid for glucose. 



Exercise 6. Add yeast to a 4 per cent. ^ sugar solution. Examine in 24 

 hours and note the formation of gas. Test for sugar. 



* Water 500 c.c. 



Glu,cosie 75 grams 



Ammonium tartrate 5 grams 



Potassium di-hydrogen phosphate 1 *gram 



Calcium chloride 5 gram 



Magnesium sulfate 5 gram 



