72
THE NATURE AND
[sect. II.
In the absence therefore of proper experiments to ascertain the force of steam,
it is difficult to determine a rule that can be depended upon for high temperatures,
and we must now try to discover if the force of other vapours will afford any
further insight into the subject.
Of the elastic Force of the Vapour of Alcohol.
104. The elastic force of the vapour of alcohol, or spirit of wine, has been
tried by several philosophers. The greater part of the experiments were made in
Temperature of
the steam.
Elastic force of steam in inches of mercury.
Dr. Ure’s
experiments.
Mr. Ivory’s
formula.
Various experiments.
By our Rule
page 59.
32°
0-2
0-185
0-16
Creighton
0-172
50
0-36
0-36
0-37
70
0-726
0-721
0-78
90
1-360
1-378
1-53
110
2-456
2-634
2-79
130
4-336
4-408
4-81
150
7-530
7-424
7-94
170
12-05
12-05
12-60
190
19-00
18-93
19-35
210
28-88
28-81
28-86
230
43-10
42-63
41-51
Taylor
42-00
250
61-90
61-50
60-0
Southern
59-79
270
86-30
86-70
82-5
Taylor
83-45
290
120-15
119-9
114-5
Taylor
114-40
310
161-30
162-8
154-5
337
240
234
Christian 1
226-5
343-6
264
240
Southern
247-8
419
714
1050
Clement
635-0
432
1852
620
Arsberger
737-0
At a temperature of about 770° Mr. Ivory’s formula gives an elastic force equal to the
modulus of elasticity of water ; the steam would, if this were correct, be more dense than water ;
while La Tour found it required a space four times its volume to become steam at about the same
heat. Arsberger’s experiments had not been seen by Mr. Ivory, or he would have had reason
for doubting the accuracy of M. Clement’s observation ; but as it is quite unsupported either by
a description of the process, or any observations at other temperatures, its deviation in
excess both from formulae founded on a considerable range of experiments, and also from other
results, is to be regarded as a motive for doubt rather than for altering our formula. Mr. Ivory
most justly remarks, that this furnishes “ another instance of the great difficulty of detecting
general properties or laws by means of a comparison of particular results and it is a difficulty
which ought to induce mathematicians possessed of such great powers as Mr. Ivory certainly is,
to endeavour to develope the first principles, rather than investigate a formula from experiments
alone.
1 Mécanique Industrielle, vol. ii. p. 232.