synthesis is
nitrobenzoic aldehyde, so that here again we begin with toluene as a raw
material. A mixture of vanillin and benzoic aldehyde when attenuated to a
state of extreme dilution in a spirituous solvent, gives the perfume known
as "heliotrope."

Not the least romantic chapter of coal-tar chemistry is this production of
fragrant perfumes from the evil-smelling tar. Be it remembered that these
products--which Nature elaborates by obscure physiological processes in
the living plant--are no more contained in the tar than are the hundreds
of colouring-matters which have been prepared from this same source. It is
by chemical skill that these compounds have been built up from their
elemental groups; and the artificial products, as in the case of indigo
and alizarin, are chemically identical with those obtained from the plant.
Among the late achievements in the synthesis of vegetable products from
coal-tar compounds is that of juglone, a crystalline substance found in
walnut-shell. It was shown by Bernthsen in 1884 that this compound was
hydroxy-naphthaquinone, and in 1887 its synthesis from naphthalene was
accomplished by this same chemist in conjunction with Dr. Semper.

Another recent development in the present branch of chemistry brings a
coal-tar product into competition with sugar. In 1879 Dr. Fahlberg
discovered a certain derivative of toluene which possessed an intensely
sweet taste. By 1884 the manufacture of this product had been improved to
a sufficient extent to enable it to be introduced into commerce as a
flavouring material in cases where sweetness is wanted without the use of
sugar, such as in the food of diabetic patients. Under the name of
"saccharin," Fahlberg thus gave to commerce a substance having more than
three hundred times the sweetening power of cane-sugar--a substance not
only possessed of an intense taste, but not acted upon by ferments, and
possessing distinctly antiseptic properties. The future of coal-tar
saccharin has yet to be developed; but its advantages are so numerous that
it cannot fail to become sooner or later one of the most important of
coal-tar products. In cases where sweetening is required without the
possibility of the subsequent formation of alcohol by fermentation,
saccharin has been used with great success, especially in the manufacture
of aerated waters. Its value in medicine has been recognized by its recent
admission into the Pharmacopoeia.

The remarkable achievemen