250 STUDIES ON FERMENTATION. 



absorbed by the yeast. The liquid contained no more sugar, 



and the weight of the yeast, dried at a temperature of 100° C. 



(212° F.), Avas 0'44 gramme (6'8 grains). The ratio between 



the weight of the yeast and that of the sugar was, therefore, 



044 1 . . 



"^L-^ = K-y^- On this occasion, where we had increased the 



quantity of oxygen held in solution, so as to yield itself for 

 assimilation at the beginning and during the earlier develop- 

 ments of the yeast, we found instead of the previous ratio of 



i^r-. that of 7^. 

 76 23 



The next experiment was to increase the proportion of oxj'gen 

 to a still greater extent, by rendering the diffusion of gas a more 

 easy matter than it is in a flask, the air in which is in a state of 

 perfect quiescence. Such a state of matters hinders the supply 

 of oxygen, inasmuch as the carbonic acid, as soon as it is 

 liberated, at once forms an immovable layer on the surface of 

 the liquid, and so separates off the oxygen. To effect the pur- 

 pose of our present experiment, we used flat basins having glass 

 bottoms and low sides, also of glass, in which the depth of the 

 liquid is not more than a few millimetres (less than ^-inch) 

 (Fig. 63). The following is one of our experiments so con- 



Fig. 63. 



ducted: — On April 16th, 1860, we sowed a trace of beer yeast 

 (" high " yeast) in 200 c.c. (7 fl. oz.) of a saccharine liquid 

 containing 1-720 grammes (26"2 grains) of sugar-candy. From 

 April 18th our yeast was in good condition and well developed. 

 "VYe collected it, after having added to the liquid a few drops of 

 concentrated sulphuric acid, with the object of checking the 

 fermentation to a great extent, and facilitating filtration. The 

 sugar remaining in the filtered liquid, determined by Fehling's 



• [200 c.c. of liquid wei-e used, which, as containiug 5 per cent., had iu 

 solution 10 grammes of sugar. — D. C. E.] 



