322 Mr. A. J. Wilmott. Experimental Researches on 



attained without the falling curve. Here the CO2 initial diffusion effect 

 cannot reveal itself. The experimental record given is slight and brief and is 

 only intended as an illustration. Throughout the work the relations of the 

 factors light intensity and CO2 coaceutratiou conformed to Blackman's 

 exposition of the theory of limiting factors. 



The final values for the four concentrations of fig. 13 are transferred to 

 fig. 14, lower curve B, and it will be seen that they exhibit the form of the 

 two-factor limiting curve. With weak light and strong CO2 Treboux also 

 records this type of curve. 



This demonstration may suffice to establish that for our experiments, com- 

 paring CO2 and bicarbonates, it is accurate to calculate bubble rates from one 

 strength of CO2 to another on the basis of direct proportionality ; provided, 

 of course, that care is taken to ensure that light is in excess throughout. 



(B) Experiments with Sodium Bicarhonate Solutions of different Strengths. 



Experimenting with series of bicarbonate solutions one does not encounter 

 such simple regularity as with CO2 solutions. After the initial CO2 diffusion 

 effect, which occurs here also, the rate is not maintained uniform for such 

 long periods, but gradually declines. This is presumably to be attributed to 

 the local alkalinity of the solution that must result from the removal CO2. 

 Angelstein records the injurious effect of added Na2C03 in increasing the 

 alkalinity, but this effect was not detached from other complications. Escape 

 of CO2 from the upper surface of the solution would increase the alkalinity 

 of the liquid, so for the more precise experiments of the next section (C) a 

 cork lid was employed to retard this effect. For the present section we have 

 two experimental series, each of five increasing strengths of bicarbonate. At 

 each strength of solution the plant and chamber were carefully rinsed, to 

 remove adherent alkaline liquid. Such a series cannot be carried through in 

 less than two hours, so to reduce the duration of the exposure, the bubble 

 rates were only followed just to the end of the initial CO2 diffusion effect in 

 each solution. The final value adopted for each solution is not therefore as 

 firmly established as if a long series of similar values had been counted. 

 The time-sequences of these experiments are not detailed here, but the final 

 adopted values for the two series are given in fig. 15. Both Series A and B 

 were carried out with weak light (intensity = 3'5), but A with such weak 

 bicarbonate solutions that the light limiting value was not reached. The 

 points for Curve B, which is more extensive, are not very smooth, but the 

 general relation of two limiting factors reveals itself here, as with carbonic 

 acid. The data for A only presents the rising limb of the curve ; presumably, 

 had stronger solutions been used no higher bubble rate would have been 



