826 Experiments 



there seems to be something complex, the simultaneous action of 

 an organic ferment and a soluble ferment. 



4. Brewers Yeast. 



Brewers yeast is killed by compressed air, as is shown by the 

 following experiment. 



Experiment CCCCXXXIX. June 26. Pieces of very active brew- 

 ers yeast are placed: 



A, in a closed flask, normal pressure. 



B, in a flask taken to 15 superoxygenated atmospheres. 



July 21. A, decayed, with a foul odor; no recognizable trace 

 through the microscope. 



B, decompressed; good, fresh odor; seems wholesome outwardly 

 and through the microscope. However, when placed in water with 

 glucose in it, it decays without fermenting, turning acid. 



So the yeast lost all its power and life; yet it was preserved 

 from putrefaction by the very agent that killed it. 



It is not surprising then that at normal pressure, fermentation 

 by yeast proceeds more energetically than in compressed oxygen. 

 Examples: 



Experiment CCCCXL. August 6. Brewers yeast is added to equal 

 quantities of a solution of glucose, at the bottom of four similar 

 tubes: 



A, 2 left at normal pressure; 



B, 2 taken to 10 superoxygenated atmospheres. 



August 8. A, 5 cc. of liquid reduce between 20 and 30 drops of 

 blue reagent. 



B, 5 cc. reduce between 40 and 45 drops. 



So compressed yeast consumed much less sugar than the other. 



Experiment CCCCXLI. May 13. 50 cc. of glucose solution are 

 placed in two flasks, with a piece of brewers yeast of the same weight. 



A, closed, left at normal pressure. 



B, taken to 10 atmospheres of an air with 76% of oxygen; tension 

 corresponding to 38 atmospheres of air. 



May 18. A, 5 cc. of the liquid reduce 1.3 cc. of Fehling's solution. 

 B, 5 cc. reduce 5 cc. 



The liquid in which the yeast was subjected to compression 

 therefore contained much more glucose than the other. 



Experiment CCCCXLII. December 2. Into each of four tubes are 

 poured 3 cc. of a weak glucose solution and a piece of brewers 

 yeast as big as the head of a pin. 



A and A', drawn out in the flame, are kept at normal pressure. 



B and B' are taken to 18 superoxygenated atmospheres. 



December 8. Decompression; A and A' contain no trace of glu- 

 cose. 



B and B' contain 15.6 mg. of glucose. 



