The temperature at which water boils varies with the pressure. In a vacuum of 13.69 pounds below atmospheric pressure water boils at a temperature of 102.018 degrees Fahr. At atmospheric pressure, which is generally taken as 14.7 pounds per square inch, water boils at 212 degrees Fahr. At 15.31 pounds pressure above atmospheric pressure water boils at a temperature of 250.293 degrees Fahr. The relation between the boiling temperature of water and the pressure is absolute; pressure cannot be increased without also increasing the temperature of the boiling point of the water, nor can the temperature of the boiling point of the water be increased without increasing the pressure. The temperature and pressure of boiling water and the temperature and pressure of the steam in contact with it are always equal.

The relative pressure and temperature of boiling water and steam, also the volume of steam at that pressure compared to the volume of water of which it is composed can be found in Table XLIX.

Table XLIX - Boiling Point Of Water

Absolute Pressure in pounds per square inch

Boiling point of water, degrees Fahrenheit

Ratio of volume of steam to volume of equal weight of distilled water at temperature of maximum density

Pressure above vacuum in pounds per square inch

Boiling point of water, degrees Fahrenheit

Ratio of volume of steam to volume of equal weight of distilled water at temperature of maximum density

1

2

3

1

2

3

1

102.018

20623

46

275.704

563.0

2

126.302

10730

48

278.348

540.9

3

141.654

7325

50

280.904

520.5

4

153.122

5588

52

283.381

501.7

5

162.370

4530

54

285.781

484.2

6

170.173

3816

56

288.111

467.9

7

176.945

3302

58

290.374

452.7

8

182.952

2912

60

292.575

438.5

9

188.357

2607

62

294.717

425.2

10

193.284

2361

64

296.805

412.6

11

197.814

2159

66

298.842

400.8

12

202.012

1990

68

300.831

389.8

13

205.929

1845

70

302.774

379.3

14

205.604

1721

72

304.669

369.4

14.69

212.000

1646

74

306.526

360.0

15

213.067

1614

76

308.344

351.1

16

216.347

1519

78

310.123

342.6

17

219.452

1434

80

311.866

334.5

18

222.424

1359

82

313.576

326.8

19

225.255

1292-

84

315.250

319.5

20

227.964

1231

86

316.893

312.5

22

233.069

1126

88

318.510

305.8

24

237.803

1038

90

320.094

299.4

26

242.225

962.3

92

321.653

293.2

28

246.376

897.6

94

323.183

287.3

30

250.293

841.3

96

324.688

281.7

32

254.002

791.8

98

326.169

276.3

34

257523

748.0

100

327.625

271.1

36

260.883

708.8

105

331.169

258.9

38

264.093

673.7

110

334.582

247.8

40

267.168

642.0

115

337.874

, 237.6

42

270.122

613.3

120

341.058

228.3

44

272.965

587.0