414 



Dr. A. Harden and Mr. W. J. Young. [Dec. 8, 



6. Production of the Initial Rapid Evolution of Carbon Dioxide by the 

 Addition of Phosphates. 



As the result of a large number of attempts to isolate the constituent of 

 boiled juice which brings about the increase in fermentation, it was found 

 that whenever an increase was produced phosphoric acid in the form of a 

 soluble phosphate was present. The effect of the addition of soluble 

 phosphates to yeast-juice was, therefore, examined and it was found that a 

 well-marked initial rapid evolution of carbon dioxide was thus produced. 

 Since, moreover, the boiled juices employed invariably contained phosphates 7 

 precipitable by magnesia mixture, there can be no doubt that it is to the 

 presence of these that this initial phenomenon is due. Quantitative estimations 

 revealed the somewhat surprising fact that the extra quantity of carbon 

 dioxide evolved in the initial period when a phosphate or a boiled juice is 

 added, corresponds with the evolution of one molecular proportion of carbon 

 dioxide for each atom of phosphorus added in the form of phosphate. 



In order to obtain accurate results with solutions of sodium or potassium 

 phosphate, the fact that these absorb carbon dioxide must be taken into 

 consideration. Solutions of the dihydrogen salts of potassium and sodium are 

 too acid to be employed and the monohydrogen salts or a mixture of these 

 with the dihydrogen salts were always used. In every case the liquid before 

 being added to the yeast-juice was saturated with carbon dioxide at the 

 temperature of the bath, and the volume of carbon dioxide liberated by the 

 addition of excess of hydrochloric acid was ascertained in an aliquot portion. 



At the close of the fermentation the fermented liquid was acidified and the 

 residual combined carbon dioxide measured, the difference between this and 

 the original amount being subtracted from the amount evolved during the 

 fermentation. 



The results are more precise when the yeast-juice employed is an active one, 

 since when the fermenting power of the juice is low the initial period becomes 

 unduly prolonged and the calculation of the extra amount of carbon dioxide is 

 rendered uncertain. The equivalence of the carbon dioxide and phosphate is 

 established by the results contained in the following Table VI. Column 1 

 gives the observed amount of extra carbon dioxide calculated as described 

 above and reduced to grammes, and Column 2 the equivalent of the phosphate 

 added, this being estimated by precipitation with magnesium citrate mixture 

 in the boiled juice or phosphate solution. 



In Experiments 1 to 7 boiled juice was added ; in 8 to 14 a solution of 

 sodium or potassium phosphate. 



The maximum rate attained during the initial period is from five to eight 



