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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 deg. F. to 323 deg. 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 deg. F. to 280 deg.
I should fancy that the above particulars are sufficent to completely differentiate atropine from all the other mydriatic alkaloids. 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 "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 deg. F. to 280 deg. F., the appearance of which is very different to that of atropine.
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. Discovered by Geiger and Hesse in 1833. It was first obtained in the form of needles, which were much more soluble than atropine.
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.
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.
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.
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