265 



^ 4. Hovj to calculate the results. 



The difference between tlie 5''' and the 4"' reading gives : the 

 volume of the gaseous carbon dioxide, present in the apparatus at 

 the end of the fermentation. Another portion of carbonic acid 

 however is retained by the liquid and this portion too has to be 

 taken into account. Now Kluyver observed, that when sugar is 

 fermented in yeast-extract at '15° C. and 760 mm. , in 1 cc. of 

 the liquid a quantity of carbonic acid is left behind which has a 

 volume of 1.2 cc. at 0° C. and 760 mm. (provided that super- 

 saturation of the liquid is avoided). By Bohr and Bock however 

 it was pointed out that at 15° C. and 760 mm. pure water retains 

 a volume of carbonic acid, which after reduction to 0° C. and 760 mm. 

 amounts to 1.019 cc. Tiie fact that Kluyver found more, can be 

 explained by the special nature of his liquid. 



Though in our experiments the carbon dioxide was not dissolved 

 in pure water, as every fermented liquid retains alcohol, yet our 

 licjuid approaches more to pure water tlian yeast-extract. It is very 

 probable, that under these circumsrances the foresaid number falls 

 between the two numbers, mentioned above. Moreover our readings 

 were made at temperatures between 17° and 20° C. Now the 

 solubility of carbon dioxide diminishes rather rapidly, when the 

 temperature rises. After Bohr and Bock the foresaid volume becomes 

 0.878 cc. at 20° C. 



For these reasons we assume the forementioned volume, under 

 the' conditions of our experiments, to be 1 cc. This simplifies the 

 calculation. 



The total volume of carbon dioxide of 0° C. and 760 mm. now 

 can be found by reducing at first the gaseous carbon dioxide to 

 that temperature and pressure, which may be done quite efficientiv 

 by means of a table, published by Kluyver'). This done, the volume 

 of all the liquid is to be added (vi/,. the difference between the 3rd. 

 and the 1th. reading). 



Kluyver made a large number of determinations of the volume 

 of carbon dioxide (reduced to 0° C. and 760 mm.), obtainable 

 with 6 different species of yeasts from 40 mgr. of 8 different 

 sugars in the apparatus, used by him (see table XXVIll of his 

 publication). Then also the number of milligrammes of sugar, equi- 

 valent to 1 cc. of CO, at that tenqierature and under normal 

 pressure were known. We have limited our experiments for the 



I) 1. c. p. 61. 



