A Manual of the Chemistry of the Carbon Compounds

334 THJB CHEMISTRY OF
Phmyl Sulphide ^g 5 \ S is formed, together with tMophenol, by
the action of phosphorus pentasulphide on phenol, and is also produced
by the dry distillation of sodium benzenesulphonate. It is a
limpid liquid, boiling at 2 t ,l2°, and possessing a disagreeable alliaceous
smell. Nitric acid oxidizes it to sulphobenzida
Phenyl Disulpkide p«5 6 ]• Sa is obtained, 03 the first product, when
thiophenol is heated with dilute nitric acid, and forms shining white
needles. By the action of nascent hydrogen, it is again converted into
tMophenol; and by boiliug it for a long time with nitric acid, it is
oxidized to benzenesulpkonic acid.
( OH
Phmolsulplumic Acid CgHw gQ „.—Two isomerie acids having
this composition are known, both being formed by the action of concentrated
sulphuric acid on phenol. When a solution of phenol on
sulphuric acid is left for a few days, the chief product consists of
metajplierwlsd-plionic add, and only a small quantity of jpuraphenolsidphmric
add is formed; whilst, on heating the mixture gently, more of
the latter is obtained, and by exposing it to a temperature of 100°—
110°, the ineta-aoid is completely converted into the para-acid.
To obtain the free acids, the insoluble basic lead-salts are decomposed
by hydrogen sulphide, and the solution first concentrated on a
water-bath, and then evaporated in vacuo; they form needle-shaped
crystals. The meta-acid is not easily obtained perfectly pure, as on
heating its solution a part is always converted into the para-acid.
Both form crystalline salts; those of the para-acid are less soluble in
water than the meta-salts, and crystallize in different forms.
The side-chains in the ineta-acid have the position 1, 3, as on
fusion with potash it yields pyrocatechint whilst the para-acid
belongs to the series 1,4; as by fusing it with potash it is converted
into resoroia (see page 314).
(SO8H
Phnoldkulphonie Acid CM3< OH is obtained by heating phenol
(SO3H
with a large quantity of concentrated sulphuric acid for a long time.
On neutralizing the dilute solution with barium carbonate, aud evaporating
the filtrate, the barium salt CaHg.OHCSOa^Da + 4H.0 ia
obtained in large prismatic crystals. The free acid is very soluble
in water, and .crystallizes in small needles, Phenoldisulphouic acid
may also be produced by decomposing diazobenzene sulphate with
concentrated sulphuric acid. Ferric chloride colours the free acid, as
well as its salts, ruby-red.