430 
DR. ANDREWS ON THE GASEOUS STATE OF MATTER. 
Table III. — Compressibility of Carbonic Acid Gas. — 99°-5-100°-7. 
p- 
t. 
e. 
t'. 
O 
1 
0 
17-42 
5-83 
18-01 
100-39 
0-07628 
20-17 
6-04 
1 
20-97 
100-37 
0 06543 
22-37 
6-01 
1 
23-34 
100-41 
0-05880 
24-85 
6-00 
1 
26-07 
100-72 
0-05269 
27-76 
5-83 
1 
29 : 30 
100-65 
0-04687 
31-06 
5-88 
1 
33 03 
100-64 
0-04158 
34-57 
5-92 
1 
37'06 
100-62 
0-03705 
40-09 
5-94 
1 
43-50 
100-60 
0-03156 
45-99 
6-31 
1 
50-60 
100-37 
0-02712 
53-81 
6-34 
6^26 
100-33 
0-02277 
64-27 
6-34 
7^89 
100-37 
0-01857 
80-25 
6-35 
1 
96-52 
100-37 
0-01422 
105-69 
6-36 
1 
137*3 
100-37 
0 01000 
145-44 
8-73 
1 
219*0 
99-46 
0-00625 
223-57 
8-72 
1 
99-44 
0-00359 
Before discussing these results on the compressibility of carbonic acid, it will be 
convenient to have accurate data for reducing the experiments in each table to the 
same temperature. These data will be supplied when the coefficients of expansion of 
carbonic acid under varied pressures and at different parts of the thermometric scale 
are known. The determination of these coefficients will form the subject of the next 
section. 
§11. 
In the limiting case of the so-called perfect gas, which is closely approximated to 
but probably never actually realized in nature, the change of volume under a constant 
pressure would for the same range of temperature correspond exactly to the change of 
elastic force under a constant volume*. In the case of carbonic acid, Regnault has 
shown that, even at low pressures, there is a marked difference in the value of a as given 
by the two methods ; and from the experiments I am about to describe, it will appear 
that at high pressures the results diverge so widely that they must not in any way be 
* According to Rudbekg the coefficient of expansion of air between 0° and 100°, deduced from the two 
methods, is precisely the same ; according to Regnattlt there is an actual difference of part of the whole 
coefficient (Poggendorvf’s ‘ Annalen,’ vol. xliv. p. 122; Mem. de l’Acad. des Sciences, vol. xxi. p. 119). 
