Theoretical organic chemistry / by Julius B. Cohen.

  • Cohen, Julius B. (Julius Berend), 1859-1935.
Date:
1942
Catalogue details

Licence: In copyright

Credit: Theoretical organic chemistry / by Julius B. Cohen. Source: Wellcome Collection.

    32/636 (page 12)
    still narrower limits of temperature, until at length the mixture is separated into certain portions, the boiling-points of which are nearly constant, and these may be regarded as puie. Fig. S represents a series of simple and efficient fractionating columns or still-heads, a is that of Vigreux, in which the constrictions are formed by indenting the tube itself; b is Hempel’s column and consists of a long wide tube filled with glass beads; c, d, and e are columns devised by Young and Thomas, the last being useful when large quantities of liquid have to be distilled, c contains a series of glass discs fused on to a rod, which can be removed from the tube; d has a series of pear-shaped bulbs blown on the stem, and e is a wide tube with a series of constrictions in each of which a small bent glass dripping tube is suspended in a gauze cup. The following tables, I. and II., illustrate two series of fractional distillations of coal-tar naphtha containing a small quantity of paraffin boiling below 8o°; benzene, b.p. 8o°; toluene, b.p. no°; and xylene, b.p. 140°. In the first fractionation (Table I.) the distillate is collected between every 5 degrees.