1893-94.] Prof. Tait on Compressihility of Fluids. 
247 
corresponding changes of value. The new II is greater than the old 
by the pressure at the new Vq- The new e must be employed with 
the new initial volume to give the ultimate volume. The following 
data were calculated from Amagat’s Tables 13 and 19 {Ann. de 
Chimie, xxix., 1893). The first of the three volumes given for 
each temperature is that of the substance when just wholly liquefied 
by pressure. This comparison is by no means a fair one, for the 
range of volumes is very different alike in extent and in situation, 
for the different temperatures. And, from the extremely great 
compressibility of the liquid when just formed, we should expect 
to find the assumption of constant II very far from the truth. 
Carbonic Acid. 
Temp. 0° 
C. 
10° 
20° 
0 
O 
CO 
p. 
V. 
34-4 -002145 
44-4 -002338 
56-4 
-002609 
70-7 -003282 
500 
1781 
500 1826 
500 
1876 
500 1920 
1000 
1656 
1000 1685 
1000 
1716 
1000 1748 
From these 
we obtain the following sets of values of e and H : — 
0-335 
0-373 
0-424 
0-527 
420 
276 
170 
48 
The value of II, calculated from the altered formula, has, in each 
case, been diminished by the corresponding initial value oi p. We 
see that e increases with great rapidity as the temperature rises : — ■ 
but the indicated ultimate volumes of carbonic acid, under infinite 
pressure, are not much affected thereby, being respectively 
0-00143 147 150 155 
where the unit is the volume of the gas at 0° C. and 1 atm. 
The values of II are, of course, small ; and they diminish rapidly 
with rise of temperature. [The critical point is about 31°’35 C., 
which is but little above the highest temperature in the table.] 
A fairer test than the above, from one point of view at least, 
might have been based upon Amagat’s important Table 17, had it 
given data for (say) vol. = -00225 at each temperature in addition 
to those at *0025 and -0020. I have done the best I could, by 
taking the nearest data directly given in Table 13. Here are a few 
of the results obtained. 
