Lerrs & BraxE—The Carbonic Anhydride of the Atmosphere. 181 
receiver, and the tube & was filled with mercury, when C was 
closed. 
After an interval of about twenty-four hours to ensure 
diffusion of the carbonic anhydride into the air of the receiver, 
the rubber junction attached to I was pinched between the finger 
and thumb—removed from the measuring pipette by raising the 
receiver, and plugged with a glass rod. ‘The receiver was then 
unclamped, and placed upright on a table. To add the charge of 
absorbent was somewhat troublesome.’ For this purpose the 
glass rod plug was removed from the rubber junction attached to 
II (the junction being pinched during the operation), and in its 
place the nozzle of the measuring pipette containing the baryta 
solution introduced. The receiver was then held in a slanting 
position (to avoid drops of the absorbent running down JI), and 
the charge allowed to run in. The india-rubber junction was 
then carefully pinched, while the nozzle of the measuring pipette 
was removed, and the glass rod plug inserted. The determination 
was then proceeded with, as already described, for the exami- 
nation of a sample of ordinary air. 
The following series of determinations of carbonic anhydride, 
both in artificial mixtures of purified air and that gas, and of air 
itself are given in chronological order. 
Unless otherwise stated the solutions were of the strength 
lec. = Ole. CO, at N. I. P. Hence the “ carbon anhydride 
found”’ was obtained by subtractiug the volume of acid required 
from that of the baryta solution originally taken, and dividing the 
difference by 10. 
In the first of the series, with artificial mixtures, the capacity 
of the receivers is not given, as our aim was only to determine the 
actual volume of carbonic anhydride, while in the later series we 
sought also to ascertain the proportion of the gas in 10,000 
volumes of air, in order to compare the results with those of 
the determinations made with air itself. 
1 Tn some of the earlier determinations the absorbent was added to the receiver of 
purified air before adding the measured volume of carbonic anhydride: but, later, the 
method was abandoned, as it did not represent exactly the conditions met with in a 
determination with ordinary air. 
