26 
MR. J. W. CAPSTICK ON THE RATIO OP THE SPECIFIC HEATS 
By altering the position of this second tube the pressure on the gas could be varied, 
and readings taken by means of a cathetometer of a series of pairs of corresponding 
values of p and v. 
As a test of the accuracy of the calibration and the various temperature corrections, 
several preliminary experiments were made on air, which made the product pv appear 
to increase at low pressures by as much as 1 per cent. 
After re-calibrating the tube and hunting in every direction for the cause of this, 
it was at last found to be due to an error in the scale of the barometer that was being 
used. Making a correction for this, the pv of air came out quite constant, and hence 
it was concluded that the calibration of the tube and the temperature corrections 
were right. 
The following table gives the details of the experiment made on ethyl chloride. 
The first three columns give the corresponding values of pressure, volume, and 
temperature, and the last gives the quantity pvjt, which is inversely proportional to 
the specific gravity, referred to a perfect gas at the same temperature and pressure. 
Table XII. 
p- 
V. 
t. 
pv 
t + 273 
149-85 
70-2 
13-5 
3670 
205-26 
51-2 
13-6 
3667 
273-96 
38-2 
13-65 
3651 
356-64 
29-2 
13-7 
3632 
446-96 
23-2 
13-7 
3617 
511-34 
20-2 
13-7 
3603 
597-85 
17-2 
13-65 
3587 
674-97 
15-2 
13-7 
3578 
773-54 
13-2 
13-75 
3561 
These values of pvjt are plotted on the curve in fig. 11. 
0 200 400 600 SOO 
Next six determinations of the S.G. of the vapour were made with the apparatus 
