Ethyl alcohol and its aqueous, solutions form useful standard liquids for testing viscometers, within the range of viscosities obtainable. A mixture of 45 per cent. by volume of ethyl alcohol and water has a viscosity which is almost exactly four times that of water at 0°. Since the viscosity of alcohol-water mixtures passes through a maximum at this concentration, the viscosity does not change rapidly with the concentration, which is a marked advantage.

The following table is abridged from one compiled by Bingham

1 Trans. Chem. Soc, 1902, 81, 179.

2 J. Amer. Chem. Soc, 1916, 38, 2316.

3 The value 505 is given by the authors, but this appears to be an arithmetical error.

Viscosity, in centipoises, of alcohol, and of alcohol.water mixtures.

Percentage of alcohol by weight.

Temp.

0.

10.

20.

30.

40.

50.

60.

70.

80.

90.

100.

0°

1.792

3.311

5.319

6.94

7.14

6.58

5.75

4.762

3.690

2.732

1.773

10

1.308

2.179

3.165

4.05

4.39

4.18

3.77

3.268

2.710

2.101

1.466

20

1.005

1.538

2.183

2.71

2.91

2.87

2.67

2.370

2.008

1.610

1.200

30

0.801

1.160

1.553

1.87

2.02

2.02

1.93

1.767

1.531

1.279

1.003

40

0.656

0.907

1.160

1.368

1.482

1.499

1.447

1.344

1.203

1.035

0.834

50

0.549

0.734

0.907

1.050

1.132

1.155

1.127

1.062

0.968

0.848

0.702

60

0.469

0.609

0.736

0.834

0.893

0.913

0.902

0.856

0.789

0.704

0.592

70

0.406

0.514

0.608

0.683

0.727

0.740

0.729

0.695

0.650

0.589

0.504

80

0.356

0.430

0.505

0.567

0.601

0.612

0.604

-

-

-

and Jackson from the most trustworthy data available.1 The unit is the "centipoise," one-hundredth of the absolute C.G.S. unit of viscosity (" poise," from Poiseuille).

For some purposes, it is convenient to use the "fluidity"instead of the viscosity; this is the reciprocal of the viscosity expressed in poises. Thus the fluidity of 100 per cent, alcohol at 0° is 1/001773 = 564, and at 40°, 1/000834 = 1199.

Freezing points of aqueous alcohol mixtures.*

Freezing point.

Grams EtOH to 100 grams of water.

- 10°

2.65

- 2

5.5

- 3

7.95

- 4

10.6

- 5

13.0

- 6

15.3

- 7

17.8

- 8

19.8

- 9

21.9

- 10

23.6

Freezing point.

Grams EtOH to 100 grams of water.

- 120°

27.6

- 14

31.3

- 16

35.1

- 18

39.0

- 20

42.8

- 22

46.6

- 24

50.6

- 26

54.8

- 28

59.2

- 30

64.6

- 320

70.0

* Raoult, Ann. Chim. Phys. [v], 1880, 20, 221.

In a series of experiments made with a view to ascertain how far the depression of the freezing point could be used as a method of determining alcohol in dilute solutions, R. Gaunt obtained the following results.2 Beckmann's apparatus was used, and the freezing mixture of ice-water and salt kept at about - 8°.

Alcohol in 100 grams of solution Grams.

Lowering of freezing point, compared with that of water.

Calculated decrease for each 1 per cent.

of alcohol.

1.0

0.424°

0.424°

2.0

0.849

0.424

3.0

1.269

0.423

4.0

1.691

0.423

5.0

2.128

0.425

6.0

2.562

0.427

7.0

3.015

0.430

8.0

3.515

0.440

10.0

4.528

0.453

12.0

5.595

0.467

Thus with the lower percentages the lowering of the freezing point is proportional to the quantity of alcohol, but at about 7 per cent. and beyond it becomes sensibly greater.

1 " Standard Substances for the Calibration of Viscometers," Scientific Paper No. 298, U.S. Bureau of Standards, p. 77.

2 Zeitsch. anal. Chem., 1905, 45, 106.

Boiling points of aqueous alcohol mixtures.*

Alcohol per cent. by weight.

(i) At 700 mm.

(ii) At 760 mm.

(iii) At 800 mm.

0

97.72°

100°

101.44°

10

89.28

91.47

92.86

20

84.89

87.05

88.43

30

82.42

84.58

85.94

40

81.00

83.13

84.49

50

79.78

81.91

83.26

60

78.92

81.04

82.38

70

78.03

80.14

81.47

80

77.22

79.32

80.64

90

76.46

78.54

79.86

100

76.26

78.35

79.68

95.57

76.16

78.23

79.54

* Doroschewsky and Poliansky, J. Russ. Rhys. Chem. Soc, 1910, 42, 109.134.

Noyes and Warfel1 found that alcohol containing 8 to 9 per cent, of water boils at 7826° to 78.27°.