Planta has already tried to show that atropine is identical with the
daturine obtained by Geiger and Hesse, founding his opinion on facts
which we nowadays look upon as doubtful. This identity was generally
admitted by all chemists. The pharmacologists, headed by Soubeiran,
Erhardt, Schroff, and Poehl, were much more reserved in their judgment.
I thought it as well, therefore, to recommence the study of daturine,
the more so as I had already determined the incorrectness of the
long accepted point of fusion of atropine, and that my researches on
hyoscyamine convinced me that this base is an isomer of atropine,
although very analogous to it. I have also shown that Merck's daturine
differs from atropine, and is merely pure hyoscyamine. A short time
afterward there appeared a paper by Schmidt which again asserted the
identity of daturine and atropine. I therefore requested Mr. Merck, of
Darmstadt, to send me all the bases which he obtained from datura. This
eminent manufacturer was good enough to comply with my request, and sent
me two products, one of which was marked "light daturine," the other
"heavy daturine," the separation of which was effected in the following
manner: The solution of crude daturine in concentrated alcohol was mixed
with a little hot water; this treatment caused the deposition of the
"heavy daturine," while the "light daturine" remained in the mother
liquor. The "heavy daturine," of which only a small quantity is
obtainable, is far from being a body of definite composition, that is to
say, it is a mixture of atropine and hyoscyamine. If we convert the base
into a double gold salt we obtain by a single crystallization a dull
looking salt, melting at from 275° F. to 280° F., the appearance of
which is very different to that of atropine. I have succeeded
in splitting up "heavy daturine" by two different methods. By
recrystallizing the gold salt six times from boiling water, the salt of
hyoscyamine, which melts at from 316° F. to 323° F., crystallizes our
first, and by the successive evaporation of the mother liquor at last
obtain the pure gold salt of atropine, which melts at 275° F. to 280° F.
If we only want to isolate the atropine, it is better to crystallize the
free base two or three times from alcohol at 50 per cent., always taking
the earliest formed crystals.
These facts prove the presence of atropine in datura; but while Planta
and Schmidt assert that only this alkaloid is found in the plant, I have
proved that the proportion of atropine in it is but small, while its
richness in hyoscyamine is great. I think, therefore, that both Planta
and Schmidt must have worked with a mixture of atropine and hyoscyamine.
It is true that Schmidt had received pure atropine under the name
of daturine, for I have proved most conclusively that the so-called
daturine supplied by Trommsdorff, of Erfurt, is pure atropine and
nothing else. It has no action whatever on polarized light.