thoroughly, and was left to stand overnight. The next day 

 50 cM^. of the clear liquid, which was above the preci- 

 pitate was carefully pipetted and titrated with a solution 

 of HCl of about o.l N. From thèse data the total quan- 

 tity of CO2 (free and half free) could be calculated ^). 



From this titration which was repeated at every experi- 

 ment, it appeared that the water, prepared in the way 

 above described, contained in minimum 200 mgr. COg 

 pro Liter, generally the quantity was somewhat larger. 



Now. 109 mgr. KHCO3 can be obtained from the 75 

 mgr. potash which were added to the water before bubbling 

 through the COo, which KHCO3 is équivalent to 48 mgr. 

 CO2 per Liter. So the excess of 152 mgr. CO^ must 

 hâve been dissolved in the water, 



From this we see firstly, that there is an excess of 

 free CO2 (as was to be expected), which is of impor- 

 tance, because it gives the certainty that ail the K0CO3 

 has in fact been transposed into KHCO3, which is harmless 

 to the assimilation, unlike carbonate, the harmful influence 

 of which has been shown by Nathanson. 



But secondly we wish to draw attention to the fact 

 that in our experiments the total quantity of COo meant a 

 large excess. Presently we will see that in thèse experiments 

 quantities of oxygen were formed, which (in maximum) 

 are équivalent to only 4.7 mgr. CO-, pro Liter water. This 

 means a very small decrease of the quantity of COo, 

 which therefore remains practically constant during the 

 experiment. 



§3. Description of the method of the ex- 

 periments and calculation of the resuit s. 

 a. Putting in the Helodeashoots. Àfter the water has 



^) This method has been derived from the: Codex Ahmentarius, 

 No. 3 ,,Het water." 



