THEORY OF FERMENTATION 303 



have been absorbed by the yeast. The liquid contained no 

 more sugar, and the weight of the yeast, dried at a tem- 

 perature of 100 C (212 F.), was 0.44 grammes. The 

 ratio between the weights of yeast and sugar is *j^* y j T *, 

 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 developments of the 

 yeast, we found instead of the previous ratio of ^ that of 



The next experiment was to increase the proportion of 

 oxygen to a still greater extent, by rendering the diffusion 

 of gas a more easy matter than 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 purpose of our present experi- 

 ment, we used flat basins having glass bottoms and low sides, 



FIG. 5 



also of glass, in which the depth of the liquid is not more 

 than a few millimetres (less than J inch (Fie. 5). The 

 following is one of our experiments so conducted: On 

 April i6th, 1860, we sowed a trace of beer yeast (" high " 

 yeast) in 200 cc. (7 fl. oz.) of a saccharine liquid con- 

 taining 1.720 grammes (26.2 grains) of sugar-candy. From 

 April i8th our yeast was in good condition and well de- 

 veloped. We 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 facilitat- 

 ing filtration. The sugar remaining in the filtered liquid, 

 determined by Fehl ing's solution, showed that 1.04 grammes 

 (16 grains) of sugar had disappeared. The weight of the 

 yeast, dried at 100 C. (212 F.), was 0.127 gramme (2 

 grains), which gives us the ratio between the weight of 



200 cc. of liquid were used, which, as containing f per cent., had in 

 olution 10 gramme* of iugmr. D. C ft. 



