SECT. II.] 
PROPERTIES OF STEAM. 
79 
with the least range of temperature above the one convenient for condensation : to 
a vapour of this kind, heat may be applied without requiring so extensive a surface 
for the fire to act on as when water is used. 
On the other part, a fluid which has a low elastic force at a high temperature 
may sometimes be conveniently and safely applied to afford a regular heat to the 
acting vapour ; hence, it becomes difficult to say to what objects it is improper to 
extend our inquiries. 
Mr. Dalton made some experiments on the vapour of ammonia. The ammonia 
he used boiled at 140° ; and its specific gravity was *9474. It had a force of 4’3 
inches at 60° ; but on increasing the temperature, the volatile parts separated first, 
and left the rest with a greater proportion of water, requiring a still higher tem 
perature to convert them into steam : this fluid is therefore inapplicable. 
113. The force of the vapours of petroleum, and of oil of turpentine, has been 
ascertained by Dr. Ure : the following tables contain his results :— 
Experiments on the Force of Vapour of Petroleum, 1 or Naphtha. 
Force in inches of mercury. 
Force in inches of mercury. 
Temperature. 
Ure’s experi 
ments. 
Formula. 
Temperature. 
Ure’s experi 
ments. 
Formula. 
316° 
3000 
30 00 
350° 
46-86 
48-1 
320 
31-70 
31-8 
355 
50-20 
325 
34-00 
34-1 
360 
53-30 
54-8 
330 
36-40 
36-6 
365 
56-90 
335 
38-90 
370 
60-70 
62-4 
340 
41-60 
42- 
372 
61-90 
345 
44-10 
375 
64-00 
66-5 
Experiments on the Force of the Vapour of Oil of Turpentine. 2 
Force in inches of mercury. 
Force in inches of mercury. 
Temperature. 
Ure’s experi 
ments. 
Formula. 
Temperature. 
Ure’s experi 
ments. 
Formula. 
304° 
30-00 
30-00 
340° 
47-30 
50-10 
307-6 
32-60 
31-6 
343 
49-40 
52-5 
310 
33-50 
32-7 
347 
51-70 
315 
35-20 
35-3 
350 
53-80 
57-3 
320 
37-06 
38-0 
354 
56 60 
322 
37-80 
39-0 
357 
58-70 
326 
40-20 
41-1 
360 
60-80 
65-4 
330 
42-10 
43-6 
362 
62-40 
336 
45-00 
. 
1 For tlie steam of petroleum, the boiling point being 316°, the rule in logarithms is 
log. / = 6 (log. (t + 100) - 2-37291). 
2 For the steam of oil of turpentine, which boils in a tube at 304°, the rule in logarithms is 
log./ = 6 (log. t + 100) — 2-36019 )•