Correction Of Height Of Barometer For Temperature

The atmospheric pressure is usually expressed in millimetres of mercury read at, or corrected to, 0°. In practice the height, H, of the barometer is read at the temperature of the room, t, and the value at 0° calculated by means of one of the two following equations :1. H0=H - 0-000172 Ht if the scale is etched on the glass ; or

2. H0 =H - 0 000161 Ht if a brass scale is used.

In Table 86 the values of 0.000172 Ht are given for each degree from 10° to 30° and for pressures at intervals of 10 mm. from 720 to 780 mm. ; and in Table 87 the values of 0.000161 Ht for the same temperatures and pressures. If the readings are smaller than 720 mm., it is convenient to plot the corrections against the pressures from 0 to, say, 800 mm. for alternate degrees from 10° to 30° on curve paper. The correction for any pressure up to 800 mm., at any temperature between 10° and 30°, may then be easily ascertained from the diagram.

Table 86. Glass Scale. - Values of 0.000172 Ht

Height of column of mercury. t

720.

730.

740.

750.

760.

770.

780.

10

1.25

1.25

1.25

1.3

1.3

1.35

1.35

11

1.35

1.4

1.4

1.4

1.45

1.45

1.45

12

1.5

1.5

1.55

1.55

1.55

1.6

1.6

13

1.6

1.65

1.65

1.7

1.7

1.7

1.75

14

1.75

1.75

1.8

1.8

1.85

1.85

1.9

15

1.85

1.9

1.9

1.95

1.95

2 0

20

16

2.0

20

2 05

2 05

21

21

215

17

21

215

215

2.2

2.2

2.25

2.3

18

2.25

2.25

2.3

2.3

2.35

2.4

2.4

19

2.35

2.4

2.4

2.45

2.5

2.5

2.55

20

2.5

2.5

2.55

2.55

2.6

2.65

2.7

21

2.6

2.65

2.65

2.7

2.75

2.75

2.8

22

2.7

2.75

2.8

2.85

2.9

2.9

2.95

23

2.85

2.9

2.95

2.95

30

3 05

31

24

2.95

3.0

3.05

31

315

3.2

3.2

25

31

315

3.2

3.2

3.25

3.3

3.35

26

3.2

3.25

3.3

3.35

3.4

3.45

3.5

27

3.35

3.4

3.45

3.5

3.55

3.6

3.65

28

3.45

3.5

3.55

3.6

3.65

3.7

3.75

29

3.6

3.65

3.7

3.75

3.8

3.85

3.9

30

3.7

3.75

3.8

3.85

3.9

3.95

40

Table 87. Brass Scale. - Values of 0.000161 Ht

Height of column of mercury. t

720.

730.

740.

750.

760.

770.

780.

10

115

1.2

1.2

1.2

1.2

1.25

1.25

11

1.3

1.3

1.3

1.35

1.35

1.35

1.4

12

1.4

1.4

1.45

1.45

1.45

1.5

1.5

13

1.5

1.55

1.55

1.55

1.6

1.6

1.65

14

1.6

1.65

1.65

1.7

1.7

1.75

1.75

15

1.75

1.75

1.8

1.8

1.85

1.85

1.9

16

1.85

1.9

1.9

1.95

1.95

2.0

2.0

17

1.95

20

2 05

2 05

21

21

215

18

21

21

215

215

2.2

2.25

2.25

19

2.2

2.25

2.25

2.3

2.3

2.35

2.4

20

2.3

2.35

2.4

2.4

2.45

2.5

2.5

21

2.45

2.45

2.5

2.55

2.55

2.6

2.65

22

2.55

2.6

2.6

2.65

2.7

2.75

2.75

23

2.65

2.7

2.75

2.75

2.8

2.85

2.9

24

2.8

2.8

2.85

2.9

2.95

3 0

3 0

25

2.9

2.95

30

3.0

3 05

31

315

26

30

3.05

31

315

3.2

3.2

3.25

27

315

315

3.2

3.25

3.3

3.35

3.4

28

3.25

3.25

3.35

3.4

3.45

3.45

3.5

29

3.35

3.4

3.45

3.5

3.55

3.6

3.65

30

3.5

3.5

3.55

3.6

3.65

3.7

3.75

Distillation Of Acetone And n-Butyl Alcohol On The Manufacturing Scale

Joseph Reilly, M.A., D.Sc, F.R.C.Sc.L, F.I.C.

Chemist-In-Charge At The Royal Naval Cordite Factory, Holton Heath, Dorset

The Hon. F. R. Henley, M.A. F.I.C.