266 Proceedings of Royal Society of Edinburgh. [sess. 
the constants. Finally, column C has been computed from my 
own formula, in forms (given below) which are adapted to volumes 
greater and less than the critical volume, respectively. A glance at 
column B shows that, so far as the “ smoothed” data are concerned, 
the critical point should be sought slightly above 194° C. For, 
at that temperature, the pressure has still distinctly a maximum 
and a minimum value, both corresponding to volumes between 3 
and 5. Column A, calculated from the unsmoothed data, does not 
show this peculiarity. Hence I have assumed, as approximate data 
for the critical point, 
t = 194° C., p = 27-2, v = i. 
The last of these is, I think, probably a little too large; but we have 
the express statement of Drs Bamsay and Young that the true 
critical volume is about 4-06. 
From their Table II. , above referred to, I quote the first two lines 
below, giving (usually to only 3 significant figures) values of dpjdt 
at constant volume : — 
v 2 2-5 3 4 5 10 20 50 100 300 
% 1-60 0-92 -622 414 -319 -133 -056 -019 -009 -0029 
dt 
f -616 426 -320 -131 -056 -019 -009 -0029 
" alC 'i 1-65 0*90 *633 -405 
The third and fourth lines are calculated respectively from the 
expressions 
0-85 + 
JLyt 
v + 3/ v 
and 
1-05 \ 1 ^ 
v - 1*5/ v ’ 
representing the co-efficient of ( t — t) in my general formula 
1 - 
( v - v)* 
v(v + a)(v + y) 
+ R(1 + 
e \t-t 
v + a ) v 
Approximate values of the other constants are now easily obtained ; 
and we have, for the critical isothermal, while the volume exceeds 
the critical value, 
p = 27-2(1 
{v-if 
v(y + 3)(y- 0-5) 
In attempting to construct a corresponding formula for volumes 
