A Manual of the Chemistry of the Carbon Compounds

THE GHEMI8TBY OF
( § ^ } fa formed ^ heating saligenin or
salicin with hydrochloric acid. It is a yellowish amorphous powder,
Salicylaldchyde O6H4 •! QQJJ exists in the flowers of the meadowsweet
and other species of Spiraea, and in the larvae of Ohrysmela
populi It is conveniently prepared by distilling salicin with dilute
sulphuric acid and potassium diehromaia It is a mobile, colourless
liquid, possessing a fragrant smell, and boiling at 196°, At -20° it
solidifies, and when exposed to the air it assumes a red tint; it is
sparingly soluble in water. Ferric chloride colours this solution
deep-violet.
Sattcylaldehyde forms crystalline compounds with the acid
sulphites of the alkali-metals, and as phenol it forms also metallic
f OK.
compounds. The potassium-compound C0H4 •! QQJJ crystallizes from
•water in colourless plates, which, when moist* rapidly absorb oxygen
from the air. By adding a solution of copper acetate to an alcoholic
solution of the aldehyde, the compound (CgH^COHJO^Cu separates
out in shining green crystals.
When equal molecules of the aldehyde and phosphorus pentachloride
are mixed, oxyhmykne dichhride CjH^OEtyCHCla is formed,
crystallizing from ether in large hard prisms, melting at 82°, By
distilling this compound with phosphorus pentachloride, it is converted
into ehlorolmzylme dichloride CJHJCLCHCIJ, a colourless and
very refractive liquid, boiling at 229°, and possessing a peculiar odour
and pungent taste. On heating it with water to 170°, it yields 1*2
chtorobmaldehyde CjH.Cl.COH, a liquid boiling at 210°, and possessing
a pungent taste and smelL
Methyl-Salicylaldchyde CeH4 j °, Q^ 8 is formed by acting with
methyl iodide on the potassium compound of the aldehyde. It is a
liquid possessing a fragraut smell, and boiling at 238°.
Salicylic Acid, or 1'2 Qxybcnzoic Add, occurs in the flowers of several
species of Spiraea, and its methyl-ether forms the chief constituent
of oil of wiutergreen. It has been produced artificially by passing
carbon dioxide into a mixture of sodium and phenol:—
It is also formed by fusing metacresol with an excess of caustic
potash:—
( nxi f CM
(lTj I \JH . QirnxT ri ti J