154 
PROFESSOR W. RAMSAY AND DR. S. YOUNG 
43. As it was difficult to understand the reason of the great divergence between 
the heats of vaporisation found by Regnault and those calculated from our results 
we thought it possible that some error in Regnault's determinations of the vapour- 
pressures of alcohol, which were at first used as the basis of our calculations, might 
be the cause of this discrepancy. It has already been noticed that the vapour- 
densities calculated from PtEGNAULT’s results with heats of vaporisation are impos¬ 
sible ; and by taking the vapour-density as normal the calculated curve of heats of 
vaporisation approaches as near Regnault’s as is possible. Now, as the vapour- 
pressure of alcohol is a datum for the calculation of the value of s v and as this value, 
dp 
as also that of —, occurs in the equation 
an error in Regnault’s determinations of vapour-pressure, which we have at first 
employed, would have influenced all the foregoing results, and most markedly those 
at lower temperatures. We, therefore, thought it advisable to make a fresh series of 
determinations of the vapour-pressure of alcohol, and used for this purpose the 
apparatus described in the Trans. Chem. Soc., Jan., 1885. The temperatures are 
corrected for the change in volume of the bulb of the thermometer by diminution of 
pressure, which, with the particular thermometer employed, one graduated in lOths of 
degrees, by Negretti and Zambra, amounted to an apparent fall of O'2° on lowering 
pressure from 763 rams, to 20 mms. 
44. The results are as follows :— 
T. 
P. 
T. 
P. 
T. 
P. 
O 
O 
O 
-5 
8-60 
0-99 
13-00 
16-69 
35-90 
-4-67 
8-75 
1-28 
1315 
17-65 
37-90 
-4-27 
9-20 
1-63 
13-75 
18-55 
40-00 
-3-36 
9'80 
2-31 
14-20 
19-96 
43-95 
-2-50 
10-25 
2-78 
14-85 
20-86 
46"55 
-1-63 
10-75 
3-47 
15-45 
22-55 
51-45 
— 1-60 
10-90 
4-67 
16-90 
23-43 
53-95 
-140 
11-05 
5-43 
17-75 
24-46 
57-60 
-0-92 
11-35 
6-55 
18-85 
25-37 
60-50 
-0-79 
11-60 
7-65 
20-15 
26-46 
64-70 
-0-39 
11-85 
915 
22-15 
27-25 
67-60 
-043 
12-05 
10-72 
24-90 
28-03 
69-90 
+ 0-09 
12-45 
12-39 
27-60 
29-36 
75-75 
054 
12-70 
14-09 
30-60 
32-60 
90-6 
0-70 
12-85 
15-87 
34-00 
45. From these results a curve was constructed, and from it values at definite 
temperatures were read off. They are compared with those given by Regnault in 
the ‘Memoires de ITnstitut,’ vol. xxvi., p. 374. 
