Discovered by Mein in 1831 in the roots of belladonna. More thoroughly studied some time after by Geiger and Hesse, who confirmed Mein's results. Liebig next published an analysis of the alkaloid, which was afterward shown to be incorrect. He consequently modified his formula, and gave the following as the composition of atropine; CHNO. Liebig's amended analysis was afterward confirmed by Planta, who further showed that the alkaloid itself melted at 194° F., and its double gold salt at 275° F. It is worthy of remark that the first figure was considered correct until my researches proved the contrary. The physiological action of atropine, especially in relation to the eye, has been most carefully studied by several celebrated ophthalmologists, such as Graef, Donders, Bezold, and Bloebaum. Its chemical properties have also been the object of very extensive researches by Pfeiffer, Kraut, and Lassen. Pfeiffer first discovered that benzoic acid was one of the products of decomposition of atropine, and Kraut split atropine by means of baryta water into atropic acid, CHO, and tropine, CONO. Lassen, who used hydrochloric acid, discovered the true products of the splitting up of atropine, viz., tropic acid, CHO, and tropine, CHN, and proved at the same time that atropic acid is easily formed by the action of boiling baryta water on tropic acid, while hydrochloric acid at all temperatures forms isatropic acid, an isomer of atropic acid. Kraut confirmed these results, and showed that atropic acid as well as cinnamic acid gives benzoic acid by oxidation, and hydratropic acid (the isomer of phenylpropionic acid) by reduction with sodium amalgam. These results are sufficient to show that tropic acid may have one of the following two formulae.

 I II 
CH_{2}OH CH_{3} / / C_{4}H_{5}CH or C_{8}H_{5}--C--OH \ \ OOHO COOH

Fittig and Wurster, who discovered atrolactic acid, CHO, an isomer of tropic acid, gives tropic acid the second formula, while Burgheimar and myself have shown that it is the true formula of atrolactic acid. Lately we have succeeded in performing the complete synthesis of atropic acid, and the artificial preparation of atropine has been greatly facilitated since I have shown that we can easily reconstruct atropine by starting from its products of decomposition, tropic acid, and tropine.

Before my researches nothing was known of the constitution of tropine. New unpublished researches into this problem have shown that it closely resembles neurine,[1] a body which I hope will speedily lead us to the complete synthesis of atropine.

[Footnote 1: As we shall probably hear a great deal about this alkaloid, it may be as well to state that, although found in the brain and liver, it may be prepared synthetically by the action of ethylene oxide, (CH)O, water, HO, and trimethyiamine, N(CH). Its constitution is that of trimethyl-ethylene-hydrate-ammonic-hydrate, and has the following constitutional formula:

 { (CH_{2})_{2}OH

{ CH_{3}

N { CH_{3}

{ CH_{3}

{ OH 

or in other words, it is the hydrate of trimethyl-hydrethylene-ammonium.]

The fusing point of atropine is not 194° F., as stated by Planta, but 237° F. Crystallized from not too dilute alcohol it forms crystals which are aggregations of prisms. Toluene, alcohol, and chloroform all dissolve atropine readily. Its double gold salt is very characteristic. It is generally precipitated in the form of an oil which solidifies rapidly and may be crystallized from hot water after the addition of a little hydrochloric acid. This clouds in cooling, and after a certain time it separates in small crystals of indeterminate form which unite in warty concretions. After drying the salt forms a dull powder, melting between 275° F. and 280° F. It also melts in boiling water, and its aqueous solution exposed to the light is partially reduced, 100 grammes of water acidulated with 10 cubic centimeters of 1.190° solution of hydrochloric acid dissolves 0.137 gramme of the gold salt at 136° F. to 140° F.

I should fancy that the above particulars are sufficent to completely differentiate atropine from all the other mydriatic alkaloids.