138 
PROFESSOR W. RAMSAY AND DR, S. YOUNG 
Densities of Saturated Vapour ([1 = 1 ). 
T. 
(1.) 
(2.) 
(3.) 
GO 
O 
110-0 
36-0 
36-7 
[29-1 
L 32-8 
< 
f 29-5 
[32-8 
130-05 
29-6 
29-9 
\ 
r30-4 
31-5 
\ 
r 29-5 
[ 31 5 
140-25 
31-6 
30-9 
\ 
f 30-7 
30-9 
< 
r29-5 
L 30-7 
150-65 
30-3 
30-3 
29-6 
29- 45 
30- 0 
160-25 
32-85 
32-55 
30-15 
\ 
29-45 
29-6 
161-6 
27-2 
28-2 
29-5 
\ 
29-35 
29-5 
171-75 
29-3 
29-3 
29-4 
29-4 
181-4 
30-0 
29-1 
29-7 
29-8 
189-8 
30-8 
30-8 
30-65 
30-7 
200-0 
32-6 
32-6 
32-9 
33-1 
210-05 
36-7 
36-9 
36-55 
36-4 
220-45 
40-75 
41-05 
40-85 
40-85 
225-05 
43-1 
43-2 
43-3 
43-4 
230-35 
46-7 
46-7 
46-7 
46-85 
232-6 
48-8 
48-8 
48-9 
48-9 
234-7 
51-2 
51-2 
50-8 
50-9 
235-85 
52-15 
52-25 
52-35 
52-35 
236-8 
54-0 
53-8 
53-7 
53-8 
237-95 
55-4 
55-55 
55-75 
55-55 
239-0 
/ 57-9 
157-5 
f 57-6 
l 57-4 
57-7 
57-7 
240-1 
60-55 
60-55 
60-55 
60-55 
241-25 
64-3 
64"6 
64 5 
64-5 
242-25 
69-1 
69-1 
69-8 
69-8 
242-6 
76-45 
76-75 
76-65 
76-65 
23. It is evident, on inspection of this and the preceding table, that the results at 
lower temperatures are not nearly so accurate as those at higher. The cause of this is 
that an error in the specific gravity of the liquid, which would have almost no effect 
on the vapour-densities at higher temperatures exercises a serious influence, for it will 
be remembered that the weight of the vapour is deduced from the total weight of 
substance and the weight of the liquid, while the weight of the liquid is deduced from 
its specific gravity and its volume. As the difference between the total weight and 
the weight of the liquid is very small, the ratio of the error in the weight of the 
liquid, and therefore of the vapour, to the total weight of vapour is a large one. 
24. The preceding table also shows that the vapour-density decreases very rapidly 
at first, and afterwards more and more slowly with fall of temperature, from the 
highest temperature to about 180°. Below that temperature the results were not 
certain enough to enable us to decide positively whether the density of the saturated 
vapour remains constant during a considerable fall of temperature or whether it begins 
to increase slowly. Determinations shall be described further on which elucidate 
this point. It is one of extreme importance, for an increase of vapour-density 
