Table 113. Fractionation of Fusel Oil Distillate with Lessing Contact Ring Still-head

Fraction No.

Temperature. ° C. corr.

Percentage by vol. Total.

Percentage by vol. Fraction.

Specific gravity.

Refractive index

I.

78.0-87.4

9.5

9.5

0.858

1.3714

II.

87.4-88.6

19.5

10.0

0.870

1.3745

III.

88.6-89.0

24.6

5.1

0.872

1.3750

IV.

89.0-89.5

46.9

top layer 20.1 water 2.2

0.861

1.3800

V.

89.5-107.2

50.6

3.7

0.814

1.3900

VI.

107.2-117.0

58.2

7.6

0.808

1.3921

VII.

117.0-130.0

62.3

41

0.814

1.4005

VIII.

130.0-131.0

69.8

7.5

0.815

1.4029

IX.

131.0-131.4

92.4

22.6

0.814

1.4034

X.

steam distillate

95.5

3.1

0.832

XI.

residue in flask

98.6

3.1

0.822

loss

(100.0)

1.4

With a rate of distillation of 5 c.c. per minute, the results shown in Table 113 were obtained by Dr. Lessing, who kindly supplied the curves. The volume distilled was observed for every rise of 0.2°. The fractions taken off were tested for specific gravity and refractive index and these results are also recorded.

The most striking feature of the curve is the right-angle formed after 46.9 per cent is distilled over. The much sharper separation of the azeotropic isobutyl alcohol-water mixture from the anhydrous isobutyl alcohol than that of the isobutyl alcohol from the amyl alcohol is also very marked. Chemical evidence shows that the residue remaining in the flask and still-head at this point is absolutely anhydrous.

The first three fractions are apparently aqueous mixtures of .propyl and isobutyl alcohol, with possibly traces of ethyl alcohol in the forerunnings. The appearance of undissolved water in the distillate was observed repeatedly at 89.0° with considerable sharpness. The fraction then coming over consists of saturated isobutyl alcohol forming a top layer over water. As soon as the last drop of water is removed, the remainder of the isobutyl alcohol distils over in anhydrous condition and leads rapidly to the isoamyl fraction.

FlG. 128.

FlG. 128.

The residue in the flask at the end of the distillation amounted to 3.1 per cent, and a similar quantity was recovered by steam distilling the still-head.

It should be noted that the results obtained with the 12 pear-bulb still-head are not directly comparable with those of the ring still-head, as the former was only 45 cm. high with a maximum diameter of the bulbs of 3.5 cm.