Atropine is an alkaloid extracted from the root of the deadly nightshade (Atropa Belladonna). The following, according to Cooley, are the principal recognized methods of preparing the alkaloid: -

(1) Belladonna root, recently dried, and in coarse powder, 2 lb.; rectified spirit, 10 pints; slaked lime, 1 oz.; diluted sulphuric acid, carbonate of potash, of each a sufficiency; chloroform, 3 fl. oz.; purified animal charcoal, a sufficiency; distilled water, 10 fl. oz. Macerate the root in 4 pints of the spirit, for 24 hours, with frequent stir* ring. Transfer to a displacement apparatus, and exhaust the root with the remainder of the spirit by slow percolation. Add the lime to the tincture placed in a bottle, and shake them occasionally. Filter, add the diluted sulphuric acid in very feeble excess to the filtrate, and filter again. Distil off 3/4 of the spirit, add to the residue the distilled water, evaporate at a gentle heat, but as rapidly as possible, until the liquor is reduced to 1/3 of its volume and no longer smells of alcohol; then let it cool. Add very cautiously, with constant stirring, a solution of carbonate of potash, so as nearly to neutralize the acid, care, however, being taken that an excess is not used. Set to rest for 6 hours, then filter, and add carbonate of potash in such quantity that the liquid shall acquire a decided alkaline reaction.

Place in a bottle with the chloroform; mix well by frequently repeated brisk agitation, and pour the mixed liquids into a funnel furnished with a glass stop-cock. When the chloroform has subsided, draw it off by the stop-cock, and distil it on a water-bath from a retort connected with a condenser. Dissolve the residue in warm rectified spirit; digest the solution with a little animal charcoal; filter, evaporate, and cool until colourless crystals are obtained.

(2) Expressed juice of belladonna is evaporated over a water-bath to the consistence of an extract, and then triturated in a marble or porcelain mortar with a strong solution of caustic potash; the resulting mass is digested and well agitated for some time, at the temperature of 75° to 80° F. (24° to 27° C), with benzole, q. s.; and after repose, the benzole solution is carefully separated, and its volatile hydrocarbon is distilled off by the heat of a water-bath; the residuum in the retort is now exhausted with water acidulated with sulphuric ncid, and the resulting "acid solution," after filtration, precipitated with carbonate of soda; the precipitate is crude atropine, which is collected on a filter, pressed between folds of bibulous paper, and dried; after which it is purified by one or more re-solutions in alcohol, and crystallizations, which may or may not be modified in the manner noticed. The proportion of potash should be about 1 dz to every quart of the expressed juice. An excellent and economical process.

The product is 0.8 to 4 per cent, of the weight of the plant from which the juice has been obtained.

(3) Belladonna root (fresh-dried and coarsely powdered) is exhausted by alcohol (0.882 sp. gr.); slaked lime (1 part for every 24 of the dried root employed) is then added to the tincture, and the whole digested, with agitation, for 24 hours; sulphuric acid is next added, drop by drop, to slight excess, and, after filtration, rather more than 1/2 the spirit is removed by distillation; . a little water is now added to the residue and the remainder of the alcohol evaporated as quickly as possible by a gentle heat; after again filtering, the liquid is reduced by further evaporation to the 1/12 part of the weight of the root employed, and a concentrated solution of potash dropped into the cold-liquid (to throw down a dark greyish brown matter), carefully avoiding excess, or rendering the liquid in the slightest degree alkaline; in a few hours, the liquid is again filtered and carbonate of potash added as long as a precipitate (atropine) falls; after a further interval of 12 to 24 hours, this precipitate is collected and drained in a filter, and after pressure between folds of blotting-paper, dried by a very gentle heat-. It is purified by making it into a paste with water, again squeezing it between the folds of blotting-paper, drying it, re-dissolving it in 5 times its weight of alcohol, decolorizing it with pure animal charcoal, distilling off greater part of the alcohol, and evaporation and crystallization by a very gentle heat; or only about 1/2 the spirit is distilled off, and 3 or 4 times its volume of water gradually agitated with it, the resulting milky liquid being then heated to boiling, and allowed to cool very slowly, when nearly the whole of the atropine crystallizes out after a few hours.

The same may be effected by at once agitating 6 or 8 volumes of water with the alcoholic solution, and setting aside the mixture for 12 to 24 hours, by which time the crystallization will be completed. This process originated with Soubei'ran, was improved by Mein, and subsequently, with slight modifications, adopted by Liebig. The product is about 0.3 per cent, of the weight of the root operated on.

(4) The filtered tincture is precipitated with iodine dissolved in an aqueous solution of iodide of potassium; the resulting ioduretted hydriodate of atropine is decomposed by zinc-and-water; the metallic oxide is separated by means of carbonate of potash; and the alkaloid thus obtained is dissolved in alcohol, and crystallized. (Bouchardat and Cooper.)

(5) The dry leaves of belladonna are gently boiled for two hours in distilled water just sufficient to cover them, and the resulting decoction is strained through a coarse cloth into a large precipitating jar; this process is repeated with a second quantity of distilled water, and the two decoctions are mixed; concentrated sulphuric acid is now added in the proportion of 2 dr. to every lb. of leaves operated on, by which the vegetable albumen of;he decoction is precipitated, and the liquid becomes clear and sherry-coloured; the clear liquor is decanted or siphoned off, and if necessary filtered; the filtrate is decomposed by either passing a stream of gaseous ammonia through it, or by suspending in it a lump of carbonate of ammonia. The effect is that the liquid turns black, and crystals of atropine are slowly formed and deposited. At the expiration of a day or two, the supernatant mother-liquid is removed with a siphon, and the crystals are thrown on a filter to drain and dry. It may be purified by re-solution and crystallization. 1 lb. of leaves yields 40 gr., or at the rate of 0 • 57 per cent. (Luxton.)

(6) To 1 qt. of the crystallized juice of the plant (previously heated to coagulate its albumen, filtered, and allowed to cool) is added 1 dr. caustic potash and 1 oz. chloroform; the whole is then agitated well, and after 1/2 hour's repose, the supernatant liquor is poured from the discoloured chloroform, which, after being washed with distilled water as long as it gives any colour to it, is placed in a small retort, and the chloroform distilled off by a water-bath; the residue is dissolved in a little water acidulated with sulphuric acid, and precipitated by potash carbonate in slight excess; the precipitate is re-dissolved in alcohol, and the solution, by spontaneous evaporation, yields crystals of atropine. (Rabourdin.)

(7) The expressed juice of the fresh, or watery extract of the dry plant, is treated with caustic soda in slight excess, and agitated with 1 1/2 .times the volume of ether; the atropine taken up by the ether is re-deposited after repose for some time, and purified by repeating the treatment with fresh ether as often as necessary. (Ure.)

(8) Freshly precipitated hydrate of magnesia is added to the coagulated and filtered expressed juice, and the mixture evaporated to dryness as quickly as possible in a water-bath; the residue is pulverized and digested in strong alcohol, and the clear liquid allowed to evaporate spontaneously. The crystals may be purified by repeated re-solutions in alcohol.

(9) The following improved process is recommended by A. W. Gerrard, who notices several objections to preceding ones. Pack 1000 grm. of well powdered belladonna leaf or root in a percolator, and allow it to macerate 24 hours with 1000 cc. of 84 per cent, alcohol; now add in parts of 250 cc. at intervals of about 4 hours, another 1000 cc. .of alcohol; when percolation ceases, displace with water, recover the alcohol by distillation, and treat the extract with 5 times its volume of water; carefully separate the resin and fatty matter, and wash it twice, mixing all the washings; evaporate them to 300 cc. and add a good excess of ammonia; expose in a shallow dish for some hours that excess of ammonia may volatilize; now shake well with an equal volume of ether, separate the ether, and withdraw the atropine from it by shaking with a small volume of water and repeated additions of acetic acid. Working in this way, the ether may be used continuously to extract the motherliquor until it is exhausted. The acetic solution of atropine is now shaken with and filtered through a little animal charcoal,concentrated to a small volume, treated again with ammonia, and dissolved out a second time with ether.

Allowing the ether to spontaneously evaporate, the atropine will separate in exceedingly fine filamentous crystals of a satiny lustre and almost white. Two more crystallizations will render them quite white. In conducting this process, it is important to remove the whole of the alcohol from the tincture, also to employ ether free from alcohol. (Pharm. Jl.[3] xii. 346.)