142 
PROFESSOR W. RAMSAY AND DR. S. YOUNG 
mann’s, 23 - 25 ; both of which agree well with our results. In these calculations our 
values of ^ were employed. 
31. Herwig gives a formula by which the volume of 1 gram, of saturated vapour 
of various liquids may be calculated from the known value of PV when constant. 
This formula is 
_v _ PY 
Vl s 0'0595^/ cc + t.ps 
Where v 1 is the vol um e of 1 gram; 5 the mass of substance; a, 273; t, tempera¬ 
ture centigrade; and p, vapour-pressure at temperatui'e t. Although this formula 
does not hold in the least at high temperatures, we give the results for alcohol calcu¬ 
lated by Herwig, at temperatures within the limits of which Herwig states that his 
law holds good. (Herwig states that the alcohol he used contained a trace of water.) 
T. 
P. 
(Heewig) 
dp 
dt 
(from Regnault) 
L. 
V.D. 
O 
23 
50-23 
7977-9 
2-99 
225-85 
22-97 
30-5 
77-58 
5237-9 
4-34 
219-15 
23-23 
36-4 
108-0 
3798-4 
5-80 
216-4 
23-46 
41-9 
144-7 
2828-9 
7-46 
211-06 
23-93 
47-8 
196-5 
2125-0 
9-68 
209-55 
23-90 
57-8 
315-8 
1342-7 
14-52 
204-72 
24-28 
62-9 
396-83 
1076-6 
17-81 
204-39 
24-48 
69-9 
537-63 
802-4 
22-98 
200-55 
24-76 
If the vapour-densities were continued to lower temperatures they would mani- 
civ 
festly fall below the lowest possible. Had our values of ~ been substituted for those 
of Regnault, the discrepancy would have been even greater. 
The numbers of Andrews, and of Favre and Silbermann, are fairly concordant, 
and appear to indicate a vapour-density of 23'25 to 23 A at normal pressure ; and it 
will be seen that a continuation of the curve obtained by us might hit this number 
at 78-4°. 
It appeared desirable to confirm this view by further experiments in which different 
methods were employed. 
32. Densities of Unsaturated and Saturated Alcohol Vapour. 
For higher temperatures the process was essentially the same as that already 
described. A much smaller amount of alcohol was used, so that it was possible to 
convert it into gas, and to increase volume until its density became normal at a high 
