128 Scientific Proceedings, Royal Dublin Society. 
wash-water drawn off into the titrating vessel in the same way 
as the absorbent. In most of our experiments the rinsing was 
repeated twice, but not more than 50 c.c. of water were used 
altogether. It should be added that during the removal of- 
the glass rods plugging I and II, and their replacement by the 
soda-lime tube and titrating vessel respectively, or vice versd, the 
rubber junctions were pinched between the finger and 
thumb to prevent access of air. 
Burettes.—In some of our earlier experiments ordi- 
nary burettes reading to jy c.c. were employed, but 
in the later series, where great accuracy was aimed 
at, special burettes were used of the form shown in the 
figure. 
They were graduated only at the lower and narrow 
extremity, so that very accurate readings could be made 
of volumes of acid from 37-44 c.c. As we invariably 
used the same quantity of barium hydrate solution 
in all our later determinations, viz. 50 c.c., and the 
receiving vessels contained from 2} to about 3 litres, 
the quantity of acid required was always well within 
the above limits, where fresh air was concerned, or the 
corresponding artificial mixture. In a few of the later 
experiments, however, where more dilute solutions were 
used, or larger receiving vessels, another burette of 
similar construction was employed with a range of 
graduation from 27-40 c.c. 
In our experiments with artificial mixtures of air 
and carbonic anhydride, it was necessary in the first 
place to remove the carbonic anhydride from ordinary 
air. ‘I'his was done by precisely the same method as 
that employed in making an actual determination, 
te. by adding 50 ec. of the standard baryta solution to a 
receiving vessel full of air: plugging the tubes, and after agitation 
allowing the vessel to remain at rest for about twelve hours. At 
the end of this time it was clamped in an inverted position to a 
tall retort stand, and the soda-lime tube and pinchcock attached to 
tube I, while the vacuous titrating vessel was attached to II. The 
absorbent was now drawn off, and the receiver washed out twice 
in succession with small quantities of neutralized distilled water— 
Fie. 5. 
Burerre. 
