8 



However, though the use of distilled water to which 

 potash had been added, caused a simplification of the 

 measuring of the free and half free CO.^, which will be 

 discussed further on, yet the boihng and coohng of large 

 quantities of water still took much time. 



Now I succeeded in driving the oxygen out of 

 the water in a simpler way, viz. by bubbling through 

 hydrogen, followed by C0._;. The hydrogen pushed away 

 the oxygen and afterwards was pushed away by the 

 COo, which partially bound to the potash as KHCO3, 

 partially dissolved in a free state. 



The préparation as it was at last applied was carried 

 out in this way: To 10 L. distilled water in the réser- 

 voir B (fig. 1) 750 mgr. potash was added. After this 

 the water was heated up to ± 65° C, during this heating, 

 and also when that température was reached, hydrogen 

 was kept bubbling through the water. This ail happened 

 within one hour, a hydrogen apparatus being connected 

 with the above mentioned tube g. 



Further COo was kept bubbling through the water by 

 means of the same tube g, during 2 hours, whiist the 

 water was kept permanently at ±65° C. 



Only after this was the tube g shut and the COo- 

 apparatus connected with the réservoir B in the way 

 shown in the figure. 



In order to détermine the quantity of free and half 

 free COo in this water, a flask of 100 cM^. was filled 

 (in a way to be discussed later on) with this water, which 

 as will be clearly seen, had not been flowing along the 

 Helodea-shoots. Thereupon this water was poured over as 

 quickly as possible into another bottle, the contents of 

 which were a little more than 160 cM\ Immediately 50 

 cM^. of a baryta-solution of ± 0.1 normal and 10 cM^. 

 of a BaClo-solution of ± 0.5 7o were added to it, and so the 

 flask was nearly flUed. After closing, the flask was shaken 



