DR. ANDREWS ON THE GASEOUS STATE OF MATTER. 
435 
Table VIII. (continued). 
p- 
t. 
9. 
a. 
54-33 
° 
63-57 
100-33 
0-01871 
0-02252 
0-005535 
64*96 
63-74 
100-37 
0-01480 
0-01833 
0-006512 
81-11 
63-75 
100 37 
0-01083 
0-01402 
0 008033 
106-9 
63-75 
100-37 
0-00665 
0-00986 
0-013150 
145-5 
63-70 
99*62 
0-00377 
0-00625 
0-018222 
223-0 
63-82 
99-44 
0-00277 
0-00360 
0-008402 
The coefficient of expansion, it will be observed, steadily increases with the pressure, 
till at 145-5 atmospheres it has reached the large value of (>01822. But as the pres- 
sure is further augmented, the coefficient, instead of continuing to increase, begins to 
diminish ; and at 223 atmospheres it has actually fallen to 0 , 008402, or to less than one 
half its value at 145 atmospheres. This change of direction in the value of the 
coefficient is easily explained, if we observe that carbonic acid at 64° has entered, under 
these high pressures, into those intermediate conditions which form the link between 
the gaseous and liquid states of matter. It has, in short, at 223 atmospheres, approached 
the liquid volume without liquefying, and its coefficient begins to change to that which 
belongs to the liquid state. We shall find in the course of this inquiry abundant proofs 
of the accuracy of this statement. 
§ III- 
We now proceed to consider the change in the elastic force of a gas when, the volume 
being maintained constant, the temperature is altered. As in the expansion of a gas 
under constant pressure, we have here two distinct questions to consider, both of which 
are highly important in reference to the laws of molecular action. The first question is 
the effect of increase of pressure on the value of the coefficient ; the second, the change, 
if any, of the coefficient for different parts" of the thermal scale. The apparatus required 
no modification whatever for these experiments ; but in making the adjustments for 
constant volume, the change of volume of the glass tube must be carefully allowed for, 
as the same reading by the cathetometer will not correspond to the same volume at 
different temperatures. The correction was always made by the equation given before, 
Ct=c 0 (l+$M). 
As I have already mentioned, the coefficient of elastic force under constant volume 
will be designated by a, to distinguish it from a the coefficient of expansion under 
constant pressure. In the following tables the letters p, t, and t' have the same signi- 
