The refractive index of ethyl alcohol for the line Hp is 1.3667 (Briihl).

Holmes1 has determined the indices of refraction (ND) at 15.5° for various mixtures of alcohol and water, and shows that a maximum value is given by a mixture containing 792 per cent. of alcohol by weight. An abridgment of his table of results is as follows: -

1 Trans. Chem. Soc, 1913, 103, 2165.

Molecular mixture.

Value of (ND at 15.5°.

C2H6O ........................................

1.36316

4C2H6O,H1O ......

1.36574

2C2H6O,H1O ......

1.36651

C2H6O,H1O .............................

1.36630

C2H6O,2H1O ......

1.36408

C2H6O,3H1O ......

1.36152

C2H6O,4H1O ......

1.35883

The maximum value, corresponding with the proportion of alcohol stated above, is 1.36661.

Browning and Symons1 found a maximum value of the refractive index, at 30°, with a mixture containing about 7825 per cent. of alcohol by weight.

L. W. Andrews2 gives the refractive index () of alcohol against air as 135941 ± 000001 at 25°, and the refractive constant (ND _ 1)/d as 045833, whilst (D . 1)/d == 0.45779. With the Zeiss immersion refractometer, the reading obtained was 85.30° ± 002°. The maximum value of the refractive index was given by a mixture of 207 per cent. of water and 79.3 per cent. of alcohol, corresponding with 3C2H6O,2H1O. This maximum value is 1363315 at 25°.

The indices of refraction for various mixtures of ethyl alcohol and water at temperatures between 15° and 55°, and for the sodium rays, have also been determined by Doroschewsky and Dvorschant. sehik.3 Some of the principal results are as follows: by weight.

Alcohol per cent.

N15oD.

N30oD.

N40oD.

N50oD.

N55oD.

0

1.33345

1.3318

1.3306

1.3290

1.3281

10

1.34020

1.3384

1.3368

1.3349

1.3339

20

1.34778

1.3450

1.3429

1.3406

1.3393

30

1.35470

1.3510

1.3481

1.3452

1.3435

40

1.35948

1.3550

1.3518

1.3484

1.3468

50

1.36290

1.3578

1.3543

1.3506

1.3488

60

1.36505

1.3597

1.3560

1.3522

1.3501

70

1.36645

1.3608

1.3570

1.3528

1.3505

80

1.36690

1.3611

1.3569

1.3525

1.3502

90

1.36626

1.3603

1.3561

1.3515

1.3491

100

1.36332

1.3573

1.3531

1.3487

1.3465

These authors found that the influence of temperature upon the index of refraction of the mixtures could be expressed by the equation Nt = N0l(1 + kt), where h is a constant and t°,0° denote the temperatures.

1 J. Soc, Chem. hid., 1914, 33, 819.21.

2 J. Amer. Chem. Soc, 1908, 30, 353.

3 J. Russ. Phys. Chem. Soc., 1908, 40, 908.931; Chem. Zentr., 1908, 2, 1569.71.

Dispersion of ultra.violet rays. . The refractive indices of methyl, ethyl, and propyl alcohols for rays of wave.length X = 4200 - 2150 have been measured by V. Henri.1 The molecular refractive power can be accurately represented by the formula: -

M

n2- l

=

a +βλ 20

d

n2 + 2

λ2 - λ20

The values of the constants a, β, and λ0, which hold good from λ = 6563 to .2150, are: -

a.

B..

λ0.

Methyl alcohol

8.0195

5.1132

1063

Ethyl

" ........................................

12.707

7.1734

1239

Propyl

" ........................................

17.112

10.148

1114

Electric conductivity. . The electric conductivity of ethyl alcohol, and of various mixtures of alcohol and water, has been determined by Doroschewsky and Roschdestvensky.2 They purified the alcohol by repeated distillation over quicklime, and the water by distillation from barium hydroxide, potassium permanganate, and phosphoric acid. The results obtained at 15° were as follows: by weight.

Alcohol.

Per cent.

Conductivity. (AX 106).

0.0

1.097

2.6

0.949

13.6

0.540

20.1

0.414

28.2

0.313

37.4

0.256

44.2

0.237

50.4

0.234

56.0

0.219

Alcohol.

Per cent.

by weight.

Conductivity. (A X 106).

60.4

0.223

71.4

0.235

74.6

0.238

80.6

0.248

86.3

0.235

91.1

0.215

94.9

0.196

98.5

0133

100.0

0.097

The relation between the specific conductivity, λ, and the concentration, C, of the alcohol in the mixtures can be represented by the equation λC= a constant, the value of the constant depending, however, upon the temperature, and upon the degree of purity of the alcohol and the water.

For mixtures containing 10 to 50 per cent. of alcohol, the relation between the viscosity N, the conductivity λ, and the dielectric constant D, can be represented by the equation Nλ/D = a constant.