Benzoic acid, as it exists in the resin, is the natural production of the plant from which the resin is derived.  It may also be produced artificially.  Abel found that when cumole (C_{18}H_{12}) was treated with nitric acid, so dilute that no red vapors were evolved for several days, this hydro-carbon was converted into benzoic acid.  Guckelberger has, by the oxidation of casein with peroxide of manganese and sulphuric acid, obtained as one of the products benzoic acid.  Albumen, fibrin, and gelatin yielded similar results when treated as above.  Woehler has detected benzoic acid in Canadian castor, along with salicin.  It is also formed by the oxidation of the volatile oil of bitter almonds.  Benzoate of potash results when chloride of benzoyle is treated with caustic potash.  Benzoic acid in the animal economy is converted into hippuric acid, which may by the action of acids, be reconverted into benzoic acid.

Benzoic acid should be completely volatile, without leaving any ash or being carbonized when heated.  When dissolved in warm water, to which a little nitric acid has been added, nitrate of silver and chloride of barium should produce no precipitates.  Oxalate of potash should give no turbidity to an ammoniacal solution of this acid.  When heated with an excess of caustic potash it should evolve no smell of ammonia, otherwise, it has been adulterated with sal ammoniac.  In spirit, benzoic acid is easily soluble, and requires 200 parts of cold and 20 parts of boiling water to dissolve one part of it.

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ON THE COLORING-MATTERS OF FLOWERS.

BY FREMY AND CLOEZ.

Chemists possess only a very incomplete knowledge of the coloring matters of flowers.  Their investigation involves difficulties which cannot be mistaken.  The matters which color flowers are uncrystallized; they frequently change by the action of the reagents employed for their preparation; and, also, very brilliantly-colored flowers owe their color to very small quantities of coloring matter.

On the nature of the coloring matters of flowers several opinions have been expressed.  Some observers have assumed that flowers owe their color to only two coloring matters, one of which is termed anthocyan, and the other anthoxanthine.  Others will find a relation between the green coloring of leaves, the chlorophylle, and the coloring matters of flowers.  They support their opinion generally on the results of the elementary analysis of those different bodies; but all chemists know that chlorophylle has not yet been prepared in a pure condition.  Probably, it retains various quantities of fatty and albuminous bodies.  Further, the coloring matters of flowers are scarcely known, so that it is impossible to establish relations supported by the necessarily uncertain composition of impure bodies.

Some time since the blue color of flowers was ascribed to the presence of indigo; but Chevreul has shown, in a certain way, that the blue substance of flowers is always reddened by acids; and that with indigo it is quite different, which, as is known, retains its blue color even when the strongest acids are allowed to act on it.