416 
DR. F. P. BURT AND DR. E. C. EDGAR ON 
needed for temperature equilibrium to be established after ice had been put in the 
pipette bath. The problem was attacked in two ways : in the first place, we made a 
series of measurements of the gas in the pipette on consecutive days, the interval of 
time between the introduction of ice and the setting being decreased from day to day. 
The volume expansion corresponding to these time intervals was obtained from the 
weight of mercury that had to be taken from the volume-adjuster in order to set the 
points. 
In the second place, the pressure change of the gas in the pipette was measured at 
constant volume by making a setting a short time after the introduction of ice, and 
then, keeping the lower mercury meniscus set to the point in the dead-space, 
measuring the increase in distance between the upper meniscus and its point with 
3 
2-5 
m 
a 
o 
o 
X 
2 
z 
ID 
5 
15 
110 100 90 80 70 60 50 40 30 20 10 0 
VOLUME CHANGE IN CMM 
lapse of time. This was done with a reading telescope, fitted with a Hilger 
micrometer eye-piece. The two methods yielded concordant results which were 
checked at a later date by a large number of similar measurements made with a 
cathetometer. In fig. 7, volume change in cubic millimetres is plotted against the 
time, in hours, during which the bulb had been in ice, and the resulting curve 
indicates that nearly three hours were required to establish temperature equilibrium.* 
Now each complete determination occupied from twelve to fifteen hours and was 
carried through in two consecutive days. The normal procedure was to measure and 
* The unexpectedly long time taken by the gas to attain temperature equilibrium may have been due 
to the fact that the base of the bulb was supported by a small rubber cork which protected the glass over 
a small area from direct contact with the ice. 
