A Manual of the Chemistry of the Carbon Compounds

442 TBB OHEMIHTBY Of
acids. It crystallizes from acetic aoid in yellow silky plates, melting
above 280°.
Plumanthrcne-hydroqirinone CUH8(OH)8 is readily obtained in
colourless crystals by heating the quinone with aqueous sulphurous
acid. It is very readily oxidized, being first converted into a darkbrown
quiohydrone, and then into the quinone. By heating it with
acetic anhydride it yields the compound 014H8(0C2Hj0)2, crystallizing
from benzene in colourless plates, melting at 202°.
f OH
Phmanffirene-qzdnme-sodium Sulphite CUH8 -J Q^Q JT + 2HgO.~
The quinone dissolves readily in a warm solution of acid sodium sulphite,
and, on cooling, this compound crystallizes out in colourless
plates; it is easily decomposed by alkalis and acids.
By means of this reaction, the crude quinone can be easily purified,
and it may also be used for detecting the presence of phenanthrene
in coal-tar. This is done by oxidizing the portion boiling
between 310° to 360° with glacial acetic acid and chromic trioxide,
and treating the product, first with soda to remove acids, and then
with a solution of acid sodium sulphite, which dissolves only phenanthrene-quinone;
on adding hydrochloric acid to the solution, the
quinone is re-precipitated,and can be recognized by its properties.
DipUnie Acid C12H3(CO2H)2 is formed by.boiling the quinone for
some time with dilute sulphuric acid and potassium dichromate. It
crystallizes from hot water in transparent compact prisms, melting at
226°, and subliming in long transparent needles. By heating it with
lime it is resolved into water, carbon dioxide, and diphenylene
ketone:—
C6H«.CO.OH CaH4
I = | >CO + CO2 + H2O
COHCO + HOK = I
C.H/ 69H6
Plwiiy&enaoic Acid is isomeric, with paraphenylbenzoic acid (page
425), and crystallizes from boiling water in small ramified needles,
resembling hoar-frost, and melting at 110°. On cooling the fused
acid quickly, it is obtained as a viscid, transparent mass, which
remains in that state for days, but becomes crystalline again by stirring
it up with a platinum-wire. By heating the acid with lime,
diphenylene ketone is regenerated, while, by distilling the calciumsalt,
diphenyl is formed.