
" Determination of Atmospheric Carbon Dioxide. 113 
which passes a short wide tube B of 2°5 cm. diameter, opening out 
into the cylinder below, and having a side tube } which can be connected 
with the aspirator, or the aspirator and meter if 
measurements of the air are required. The upper 
part of the tube B is closed with a cork, through 
which passes a narrower tube C terminating below 
in a funnel, the width of which is only slightly 
less than that of the cylinder. The mouth of © 
the funnel is closed with a perforated porcelain 
disc, which is luted in with paraffin. When air is 
aspirated through the side tube 0 it enters the 
apparatus down the narrow tube c, and passing 
through the perforated plate, impinges as a tur- 
bulent stream on the surface of the absorbing 
solution of caustic soda at d. In order to distri- 

bute the air more completely, a small cone of 

paraffin e is supported on a needle in the position 
shown in the Figure. The funnel can be adjusted 
to any desired distance from the surface of the 
liquid in the cylinder, the ordinary working 
distance being 1 cm. 100 cc. of a solution of 



caustic soda of approximately 4 per cent. concen- 
tration are introduced into the cylinder through 
an india-rubber cap temporarily placed over its mouth, and a similar 
arrangement at the close of the experiment admits of the liquid being 
titrated without removal to another vessel.* At the point reached in the 
cylinder by 100 c.c. of liquid, the area exposed was 32°557 sq. cm. 
Hart’s method of double titration was used for determining the carbon 
dioxide absorbed by the alkali ; this has been already fully described. 
In determining the constants of the above apparatus the air-current 
employed was divided into two parts, one of which passed through the surface 
absorber, and the other through a Reiset’s tower charged with the solution of 
caustic soda by means of which an independent and accurate determination 
of the carbon dioxide was obtained. In both cases the volumes of air passed 
were measured by standardized meters. 
The first series of experiments, of which the results are given in the follow- 
ing Table, was undertaken for testing still further the accuracy of the above 
* Care must be taken not to wet the sides of the cylinder above the level of the liquid. 
t See ‘Phil. Trans.,’ B, vol. 193 (1900), p. 289; also ‘ Roy. Soc. Proc.,’ this vol., p. 35. 
VOL. LXXVI.—B. I 
