62
THE NATURE AND
[sect. II.
94. The next point is to compare the formula with experiment; and we shall
commence with Mr. Watt’s experiments on salt water. The water was nearly
saturated with salt: it was more free from air than common water, but it parted
with difficulty from that which it contained. The results compared with the
formula for saturated salt are shown in the following table.
Watt’s Experiments on the Steam from Salt Water.
Temperature.
Force in inches of mercury.
Temperature.
Force in inches of mercury.
Watt’s observa
tions.
Formula for satu
rated solution. 1
Watt’s observa
tions.
Formula for satu
rated solution. 1
46°
001
0-24
195°-5
15-34
16-64
85
0-58
1-00
201-5
17-16
18-77
113
1-72
2-33
207
19-34
20-92
139
354
4-66
210
21-8
22-18
160
6-27
7-72
212
22-74
23-05
169
8-12
9-47
216
24-6
24-87
180
10-85
1204
218
25-52
25-84
187
12-67
13-01
220
26-5
26-84
In these, as in all the early experiments on the force of steam, the force is less
than it ought to be at low temperatures.
Mr. Watt’s experiments on pure water afford a like discrepancy, as will be found
by comparing the following table of results taken at random out of his series. 2
Watt’s Experiments on Pure Water.
Temperature.
Force in inches of mercury.
Watt’s observa
tions.
By our Rule,
page 59.
55°
0-15
0-45
118
2-68
3-59
18Ò
14-73
15-67
• 225
37
38-32
240
49
50-24
261
68
72-00
272*5
82
86-89
rated water from the bottom, or lower part of the boiler, by means of a pump, and subsequently by
means of their blow-off pipes and cocks, now generally followed : the operation of blowing off is
usually attended to every three or four hours.
1 The results in this column are calculated by the Rule i, by logarithms, given at page 59, with
this difference, that instead of subtracting 2-24797 as for common water, the number 2-26703, as
given in the preceding table, is used for saturated solution.
2 Robison’s Meehan. Phil. vol. ii. p. 32—34.