A Manual of the Chemistry of the Carbon Compounds

160 THE CHEMISTRY OF
EROm-GROUP.
Primary Propyl Alcohol CaHj.OH occurs in small quantities in
the fusel-oil of beetroot spirit, corn spirit, and cognac. To isolate
it the fusel-oil is subjected to fractional distillation, and the portion
boiling between 80° and 105° collected separately. This is a
mixture of ethyl, propyl, and isobutyl alcohols, which cannot be
separated by fractional distillation, as their boiling-points are too
close together.
Boiling-point.
Ethyl Alcohol 78*4
Propyl Alcohol 97
Isobutyl Alcohol . . . . . . 108
The liquid is therefore acted upon by phosphorus and iodine or
bromine, to obtain the iodides or bromides, the boiling-points of which
differ much more, so that it is easy to obtain pure compounds by fractional
distillations. The boiling-points of these compounds are:—
Ethyl Iodide . . . 72" Ethyl Bromide . . . 39°
Propyl Iodide . . . 102 Propyl Bromide . . 71
Isobutyl Iodide . . 121 Isobutyl Bromide . . 92
The bromide or iodide of propyl is next heated in sealed tubes
with concentrated acetic acid and potassium acetate, and the propyl
acetate thus formed is converted into the alcohol by heating it with a
solution of potash. On distillation, aqueous propyl alcohol is obtained,
which may be rendered anhydrous by a similar method to that
by which absolute alcohol is obtained.
Propyl alcohol has also been obtained by synthesis from ethyl
alcohol. It is a light colourless liquid, resembling common alcohol;
on oxidation it yields propmMdehyie C3H00, a liquid boiling at 50°,
and propionic add,
Propionio Acid 8 6 JT f O is best prepared by boiling propionitrile
with an alcoholic solution of caustic potash as long as ammonia is
given off. The solution is then evaporated, and the residue distilled
with diluted sulphuric acid. Propionic acid is a colourless liquid
boiling at 140°, and having an add smell. It mixes with water in
all proportions, but by adding calcium chloride to the aqueous solution,
the acid separates as a light oily layer. From this property
its name has been derived, being the first member of the series
showing the properties of a fsX (irp&jov Trwv). Amongst the salts,
lead propionate Pb(C3H6O2)2 is most characteristic; it is very soluble