86 
Mr Rudge, On the Specific Heat of Gases 
In the final experiments by this method, twelve bulbs con- 
taining about 50 grams of the gas were used. The pressure of the 
gas was calculated from the following data : — The average weight 
of gas in a bulb was 4'5 grams, and the internal volume was 
6'25 c.c. At 40° the amount of gas at atmospheric pressure 
would occupy a volume of about 2620 c.c., the internal pres- 
2620 
sure being consequently = 420 atmospheres, approximately. 
D ZD 
Amagat has shown that at 400 atmospheres pv for C0 2 is about 
the same value as at 1 atmosphere, i.e. Boyle’s law holds good. 
Between two and three hundred determinations were taken by 
this method, giving values for the specific heat of the gas, which 
varied from '4 to ’68, the mean value being '59. It was felt, how- 
ever, that there were several small sources of error such as 
radiation losses, which were difficult to allow for, although it 
seemed that these should not exceed 10 per cent. 
Then another method of working was tried. The contents of 
the calorimeter were heated by a current passing through a 
coil of Eureka wire immersed in the liquid. A calorimeter was 
constructed of thin copper, having a fiat spiral of Eureka wire 
placed at the bottom. The bulbs were contained in a wire gauze 
cage, suspended upon a steel axis fixed to the calorimeter, which 
had a closely fitting lid, through which the rod attached to the 
cage, passed for the purpose of setting it in rotation. 
If a constant electric current were sent through the coil, it 
would heat the contents of the calorimeter, and as long as the heat 
capacity of the whole remained constant, it might be inferred that 
in different experiments lasting for equal periods of time, and 
acting through the same range of temperature, the same amounts 
of heat would be involved. If, however, the heat capacity of the 
calorimeter and its contents varied, then the rise in temperature 
would be inversely proportional to the capacity. 
The measurements were made as follows : — 
(1) After weighing the bulbs and placing them in position 
in the calorimeter, the latter was filled with sufficient paraffin to 
cover the bulbs. The calorimeter was placed in a thickly- 
wadded case, and the bulbs set in rotation. A current was then 
sent through the wire and observations of the temperature taken 
at definite intervals of time. 
(2) The gas was then removed from the bulbs by piercing 
a small hole which was afterwards soldered up. The empty bulbs 
were weighed in order to find the weight of gas formerly present. 
The bulbs were then returned to the calorimeter, care being taken 
to have exactly the same amount of paraffin as before. The 
current was sent through the coil and the observation of tempera- 
