DE. ANDREWS ON THE GASEOUS STATE OF MATTER. 
431 
confounded with one another. For the sake of precision, I propose to designate by ot 
the coefficient of expansion for change of temperature under a constant pressure, and 
by a! the coefficient of elastic force for change of temperature under a constant volume. 
We shall confine our attention in this section to the determination of the values of a 
under varied pressures and at different parts of the thermal scale. 
In the next table the results are given of a set of experiments I have made to deter- 
mine the average coefficient of expansion for heat of carbonic acid from 0° to about 7°‘5 
under pressures varying from 12 to 34-5 atmospheres. For this range of temperature 
the pressures could not be carried higher, on account of the liquefaction of the gas. 
In this table p is the pressure as indicated by the air-manometer, t the temperature 
of the manometer, and v 1 the volume in cubic centimetres of the carbonic acid at the 
pressure^? and temperature f. 
Table IY. — Values of a from 0° to 7 0, 5. — Constant Pressure. 
V • 
t. 
t/. 
t'.. 
a. 
12-02 
O 
7-53 
0-07298 
7-54 
0-00462 
12-00 
6-73 
0-07065 
0-00 
16-22 
7-65 
0-05243 
7-64 
0-00520 
16-25 
6-65 
0-05031 
0-00 
20-10 
7-61 
0-04108 
7-63 
0-00607 
20-09 
6-64 
0-03928 
0-00 
24-81 
7-63 
0-03192 
7-64 
0-00700 
24-80 
6-64 
0-03031 
0-00 
27-70 
7-44 
0-02773 
7-45 
0-00782 
27-66 
6-47 
0-02627 
0-00 
31-07 
7"65 
0-02386 
7-65 
0-00895 
31-06 
6-64 
0-02234 
0-00 
34-49 
7-45 
0-02058 
7-46 
0-01097 
34-48 
6-64 
0-01903 
0-00 
In calculating the values of a in the foregoing table, the observed volume ( v ') of 
the carbonic acid at the higher temperature (7 0, 54 &c.) was in each case corrected for 
the small differences of pressure which occurred in the observations at that tempera- 
ture and at 0°. In many cases it would have been sufficient to make this correction by 
Boyle’s law ; but the exact data for the purpose being supplied by Tables I., II., and III., 
I have in these and other similar cases always employed the direct results given by 
experiment of the compressibility of carbonic acid at the pressures and temperatures 
indicated. 
In the two following tables the values of a are calculated from the results in 
Tables I., II., and III., the value of 0 in Table I. having been first reduced to 0° by 
means of the coefficients at the respective pressures given in Table IV. 
3 o 2 
