GASEOTJS AND LIQUID STATES OE MATTER 
581 
millims., would occupy at the temperature at which the observation was made under 
the pressure indicated by the air in the air-tube. The values of l are the ordinates of 
the curve lines shown in the figure, page 583*. 
Table I. — Carbonic Acid at 13°T. 
s - 
t. 
if. 
l. 
o 
47'50 
10-75 
7^16 
13-18 
234-1 
1 
4876 
10*86 
1 
80*43 
13-18 
221-7 
48-89 
10-86 
1 
80*90 
13-09 
220-3 
_2_ 
49'00 
10-86 
105*9 
13-09 
168-2 
49*08 
10-86 
1 
142*0 
13-09 
125-5 
1 
49*15 
10-86 
1 
192*3 
13-09 
92-7 
1 
49*28 
10-86 
1 
268*8 
13-09 
66-3 
1 
49*45 
10-86 
1 
342*8 
13-09 
52-0 
I 
49 63 
10-86 
1 
384*9 
13-09 
46-3 
1 
50*15 
10-86 
462*9 
13-09 
38-5 
1 
50'38 
10-86 
1 
471*5 
13-09 
37-8 
1 
54*56 
10-86 
1 
480*4 
13-09 
37-1 
75*61 
10-86 
1 
500*7 
13-09 
35-6 
1 
90*43 
10-86 
1 
510*7 
13-09 
34-9 
It will be observed that at the pressure of 48*89 atmospheres, as measured by the 
contraction of the air in the air-tube, liquefaction began. This point could not be fixed 
by direct observation, inasmuch as the smallest visible quantity of liquid represented a 
column of gas at least 2 or 3 millims. in length. It was, however, determined indirectly 
by observing the volume of the gas 0 o, 2 or 0 o, 3 above the point of liquefaction, and cal- 
culating the contraction the gas would sustain in cooling down to the temperature at 
which liquefaction began. A slight increase of pressure, it will be seen, was required 
even in the early stages to carry on the process. Thus the air-guage, after all reductions 
* As Z is the entire volume to which the carbonic acid is reduced, it does not always refer to homogeneous 
matter, hut sometimes to a mixture of gas and liquid. Its value in the example given in the text is obtained 
as follows : — 
z=i 7 ooo . Q'QQ 42 ! 1 =231.3. 
0-3095 
When Z is homogeneous, - represents the density of the carbonic acid referred to carbonic acid gas, at the 
temperature t', and under a pressure of one atmosphere. 
JVIDCCCLXIX. 4 I 
