ON THE THERMAL PROPERTIES OF ALCOHOL. 
127 
recorded will be given when treating of the compressibility of the liquid. They 
remained constant within the limits of reading during a considerable reduction of 
volume. 
8. The vapour-pressure of alcohol has been measured by Regnault up to 150°. 
On examining his tabulated results by the method of differences, it was found that 
the third differences show irregularity at and above 110°; on taking the fourth 
differences minus quantities begin to appear. We find that our numbers to some 
extent confirm this peculiarity of Regnault’s results. In order to calculate the 
pressures corresponding to even temperatures, the difference for 20°, i.e., about 10° 
below and about 10° above the temperature requiring reduction was taken ; and by 
dividing by the interval of temperature, the mean change for f 0 was found. This was 
applied to reduce the pressure at the observed temperature to what it would be were 
the numbers representing temperature multiples of 10°. The error introduced by this 
somewhat crude method must necessarily be small, inasmuch as the required change 
of temperature seldom exceeds 1°. 
From measurements, described in a later part of this paper, the vapour-pressure 
at 0° was found to be 12’24 nuns. From this number, and from those at 60°, 120°, 
180°, and 240°, constants for a formula of the type suggested by Biot were calcu¬ 
lated. The formula is:—logy> = «,-j-^ a/ +c/T. The constants are:—a= 5-0720301 ; 
log 6=2-6406131 ; log c = 0‘6050854 ; log a = 0-003377538 ; log /3=1 '99682424 (c is 
negative). 
T. 
Numbers given by Regnault. 
Numbers found 
by R. and Y. 
A. 
Numbers from 
above formula. 
Difference of 
4th place. 
O 
0 
12-70* 
12-83f 
12-24 
0 
12-24 
10 
2423 
24-30 
23-77 
+ -05 
23-73 
20 
44'46 
44-48 
44-00 
+ -03 
43-97 
2132 
30 
78-52 
78-49 
78-06 
- -05 
78-11 
2-627 
40 
133-69 
133-64 
, , 
133-42 
2-994 
50 
219-90 
219-88 
219-82 
3-417 
60 
350-21 
350-26 
350-21 
3-570 
70 
541-15 
541-21 
, # 
# § 
540-91 
3-73 
80 
812-91 
812-76 
. , 
811-81 
3-61 
90 
1189-30 
1188-43 
1194-3 
+ 
■^r 
00 
1186-5 
3-46 
100 
1697-55 
1694-92 
1692-3 
3-26 
no 
2367-64 
2361-63 
2356 
- 3-9 
2359-8 
2-90 
120 
3231 73 
3219-68 
, t 
3223-0 
2-72 
130 
4323-00 
4301-04 
4320 
+ L3 
4318-7 
2-57 
140 
5674-59 
5637-00 
5666 
- 20-6 
5686-6 
2-75 
150 
7318-40 
7258-73 
7326 
- 42-7 
7368-7 
2-79 
160 
9366 
- 43-9 
9409-9 
3-44 
170 
11856 
- 2-0 
11858 
5-94 
180 
14763 
- 1-0 
14764 
3-94 
190 
18178 
- 7-0 
18185 
9-0 
200 
22164 
- 18-0 
22182 
12-0 
210 
26821 
— 4-0 
26825 
12-0 
220 
32097 
- 99-8 
32196 
21-0 
230 
38176 
-213 
38389 
240 
45504 
- 15 
45519 
* ‘Memoires de l’lnstitut,’ vol. xxvi., p. 374 
t ‘ Comptes Rendus,’ vol. 1., 1860, p. 1067. 
