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ADVENTURES IN RADIOISOTOPE RESEARCH 



(b) Yeast containing *^K placed in nutrition solution 



The analytical data obtained in the first experiment are recorded in 

 Table 1. In this experiment, non-labelled yeast was first placed in a 

 labelled nutrient solution and, after the lapse of 2 hours, a sample of 

 the yeast and a sample of the nutrient solution were analysed. The next 

 step was to place the centrifuged yeast which now contained 42K in a 

 non-labelled nutrient solution. One sample was taken after the lapse 

 of 20, another sample after the lapse of 44 hours. Chemical and radio- 

 active analyses of the samples were then carried out. 



The results of our experiments are seen in Table 2. In columns 3, 4 

 and 5, data on the distribution of '^^K between yeast and nutrient solution 

 are given. In those cases, in which non-labelled yeast was placed in 

 labelled nutrient solution, the ratio of the ^'^K content of yeast and 

 nutrient solution of equal volumina is stated. In the converse cases, 

 the ratio of the ^^K content of nutrient solution and yeast is given. 



In column 3, the values of the distribution coefficient of ^^K are to 



be seen which we should expect to be present in the case that no exchange 



of potassium between yeast and nutrient solution took place. Due to 



the increase of the potassium content of the yeast during fermentation, 



^^K will accumulate in the yeast even in a total absence of potassium 



exchange between yeast and nutrient solution. If we denote the increment 



in the potassium content of the yeast by a, and the original ^^K content 



of the nutrient solution by h, the ratio of the ^^K content of the yeast 



a 



and the nutrient solution will work out to be . In this cal- 



h — a 



culation, the absence of a potassium exchange between yeast and nutrient 



solution is assumed. In a similar way, the corresponding figures are 



calculated in those cases in which labelled yeast is placed in non-labelled 



nutrient solution, in which a decrease will also lead to a change in the 



*2K content of the yeast without any potassium exchange taking place 



between yeast and nutrient solution. 



In column 4, the distribution coefficient is stated which we should 



expect in the case of a full interchange taking place between j^east 



