A Manual of the Chemistry of the Carbon Compounds

340 THE 0BBMI8TRY OF
Hydroquinone is prepared by heating ortho-iodophenol with potash
to 180°. This body was first obtained by suspending quinone C6H.O2
(see below) in water, and passing sulphur dioxide into it until a
colourless solution is formed:—
C A { o> + 2H *° + S0 * = C « H * { OH + S0 * H *
Hydroquinone crystallizes in rhombic prisms, melting at 172°, and
subliming with partial decomposition at a higher temperature. It
exists as glucoside, called arhdm, in the leaves of the bearberry
(Arbutus Urn uni) and other Ericaceae; when arbutin is boiled with
dilute sulphuric acid, it is resolved into hydroquinone and dextrose
;—
o C6HUO5 + 2 } ° - C « H * {OH + W ^
Hydroquinone does not yield substitution-products with bromine
and chlorine, because these elements oxidize it first to quinone. But
substituted hydroquinones are readily formed by the action of sulphur
dioxide and water on chloro- and bromo-quinones,
DinUrohydroquinone C6H2 j /jig ? •—^ v tne a^ion of concentrated
nitric acid on arbutin, dinitroarbutin is formed, which, on boiling with
very dilute sulphuric acid, is resolved into dextrose, and dinitrohydroquinone.
It crystallizes in golden-yellow plates, dissolving with a
blue colour in alkalis,
Quinone C6H44 Q>.—This compound was first obtained by oxidizing
quinic acid C6H7(OH)4COgH with manganese dioxide and
sulphuric acid; and it is also formed by the oxidation of hydroquinone
and several other derivatives of benzene.
Quinone is a very volatile body, subliming readily in brilliant
golden-yellow needles, possessing a suffocating smell, like iodine, It
is but slightly soluble in cold water, more freely in boiling water and
alcohol and ether; the solution has a yellow colour, and produces
brown stains on the skin,
( O OP IT OTT
Quinkydrone, or green, Hydroquinone C0H4 •! o OcV OH' * s f° rme( *
by the incomplete reduction of quinone with sulphurous acid, and by
the direct combination of quinone and hydroquinone. It is also produced
by adding chlorine-water gradually to a solution of hydroquinone
:—
f OH HO.C0H,.0H 2rl _ r H ( O.OC0H4.OH „ ,
4 { OE + HO.cX-OH + J01 * t(lH + 4HC1
« 10.OCX-OH
Quinhydrone crystallizes in smooth, long needles, possessing a
splendid beetle green lustre, and a faint smell of quinone, and dis-