450 Scientific Proceedings, Royal Dublin Society. 
thick-walled india-rubber tube to the measuring apparatus, which, 
in its turn, is connected with the stock-bottle of weak potash 
solution— (the carbonic anhydride content of which has been 
previously ascertained), and the upper extremity of the tube 
connected in a similar manner with the three-way stop-cock B 
attached as shown to a bottle C containing air which has been in 
contact with the solution of caustic potash (which latter the bottle 
also contains) for some hours, so that the air is freed from carbonic 
anhydride. This bottle is also connected by a siphon tube with a 
second bottle D filled with the potash solution. 
The mercury reservoir attached to the measuring tube is then 
raised and the two stop-cocks opened, so that the air in the tube 
passes out into the atmosphere and the tube itself becomes filled 
with mercury. The upper stop-cock is then turned, so as to 
connect the tube with the air in the bottle C, and the mercury 
reservoir lowered when the tube again becomes filled with air, 
which now, however, contains no carbonic anhydride. The 
measuring tube is next filled to the mark 50 c.c. with the potash 
solution contained in the stock-bottle, and this charge slowly 
transferred to the tube by raising the mercury reservoir, turning 
the lower stop-cock in the proper direction, and the upper one, so 
that the displaced air again passes into the bottle, and mercury 
just shows above the lower rubber junction. ‘The upper extremity 
of the tube is then sealed off, the tube itself inverted while still 
attached at its lower extremity to the measuring tube, then 
detached together with the india-rubber tube forming the junction. 
Tt only remains to draw off and seal the lower end (now the 
upper end), when the tube contains exactly 50 c.c. of the weak 
potash solution, together with some air, which, however, is suse 
from carbonic anhydride. 
New form of Receiver.—As an ordinary 6-litre flask is somewhat 
unwieldy and fragile, and a cork which has to be removed 
frequently is an unsatisfactory method of enclosing a definite volume 
of air within the flask, we propose to employ a bottle-shaped 
receiver of stout glass instead, provided with an accurately-ground 
hollow stopper and glass tubes blown into the latter as shown in 
the diagram (fig. 5, D.)—the extremities of these tubes to be 
plugged when necessary with pieces of thick-walled india-rubber 
tube and glass rods. 
