36 THE BIOLOGY OF THE CELL 



The gas will come through the glass tube and 

 the rubber tube over to the surface of the mer- 

 cury in one branch of the manometer, and push 

 down the mercury on that side and raise that 

 on the other. Measure the height of the mer- 

 cury, and calculate the pressure needed to raise 

 the column of mercury to this height. 



e. Formation of alcohol. — Grow some yeast in Pasteur's 



solution with sugar, in a flask closed with a cork 

 through to the lower surface of which passes a 

 glass tube about eight inches long, bent down- 

 ward at an angle of about 30°. When the forma- 

 tion of gas has entirely ceased in the flask, set 

 the latter on a water-bath and, at the lowest tem- 

 perature possible, distill the fluid into a test-tube 

 held at the end of the bent tube. When the test- 

 tube is about half full, remove the stopper and 

 bent tube from the flask, insert them into the 

 test-tube, and redistill the contained fluid, collect- 

 ing the first few drops in a watch-glass. Do they 

 give off the odor of alcohol 1 Apply a hghted 

 match to the fluid in the watch-glass to see if it 

 ignites and gives the pale blue flame characteris- 

 tic of burning alcohol. 



f. Chemical reaction of fluid yeast. — Dip the end of a 



strip of blue litmus paper (which turns red when 

 placed in an acid) into some fluid yeast. What 

 change takes place in the color of the paper ? Is 

 fluid yeast acid or alkaline in its nature ? Note, 

 also, the odor of the fluid. 



g. Temperature of yeast during growth. — Take two 



