
1905.] On the Physiological Processes of Green Leaves. 35 
error of measurement bears to the true volume. In the large Reiset’s 
‘apparatus we always employed 400 c.c. of the solution of soda, so that if the 
accumulated errors of measurement amounted to as much as 0°5 cc., a very 
unlikely value, the final estimation of the carbon dioxide could only be 
0-5 x 100 
400 
When the amount of liquid abstracted from the large apparatus for the final 
titration is 100 c.c., as is usually the case, the relation which this bears to the 
100}; V 
We 

affected to the extent of = 012 per cent. of the true amount. 
original solution is expressed by V , where V represents the initial, 
and V’ the final volume. 
The mode of transferring this 100 c.c. from the Reiset’s apparatus to the 
vessel for titration requires a word of explanation. After rapidly washing 
down the upper end of the wide tube the plug or stopper is once more 
inserted, the exit-tube being guarded with a small soda-lime tube. Air, freed 
from carbon dioxide by passage through a Winkler’s absorption-apparatus, is 
then pumped into the apparatus through one of the tubulures of the lower 
vessel by means of an india-rubber ball-pump, and the alkaline solution is 
driven into the wide tube several times in succession until the solution is 
thoroughly mixed. 
After weighing the apparatus a small tube reaching to the bottom of the 
vessel is inserted into the second tubulure, the upper part of this tube being 
then connected with a large burette which is filled from below by forcing air 
down the wide vertical tube. The titration vessel, into which the 100 cc. of 
solution is now run from the burette, is a glass cylinder of suitable dimensions 
furnished with a rubber cap having two apertures through which the ends 
of the titration-burettes can be passed. In all these operations care is taken 
that no air can come into contact with the alkaline solution unless it has 
been previously freed from carbon dioxide by passing through the Winkler’s 
apparatus, and all the open ends of the tubes and burettes are guarded with 
soda-lime tubes. 
The Titration Method. 
Although this has already been described in connection with our work on 
the static diffusion of gases,* it is desirable to give a further account of the 
method in view of its importance in investigations such as we are 
considering. 
There are grave disadvantages connected with any method of carbon 
* © Phil. Trans.,’ B, vol. 193 (1900), p. 289. 
