Coniine forms with carbon disulphide a thiosulphate and a sulphite. If carbon disulphide, therefore, be shaken with an aqueous solution of coniine, the watery solution gives a brown precipitate with copper sulphate, colours ferric chloride solution dark brown red, and gives a milky opalescence with dilute acids. If coniine itself is added to carbon disulphide, there is evolution of heat, separation of sulphur, and formation of thiosulphate. Nicotine does not respond to this reaction.
§ 320. Other Coniine Bases.—Methyl- and ethyl-coniine have been prepared synthetically, and are both similar in action to coniine, but somewhat more like curarine. By the reduction of coniine with zinc dust conyrine (C8H11N) is formed; between coniine and conyrine stands coniceine (C8H15NO). De Coninck has made synthetically by the addition of 6 atoms of hydrogen to β collidine, a new fluid alkaloid (C8H11N + 6H = C8H17N), which he has called isocicutine: it has the same formula as coniine. Paraconiine Schiff prepared synthetically from ammonia and normal butyl aldehyde; it has the formula C8H15N, and therefore differs from coniine in containing two atoms less of hydrogen. All the above have a similar physiological action to coniine. α-stillbazoline (C11H19N), prepared by Baurath from benzaldehyde and picoline, is analogous to coniine, and according to Falck has similar action, but is more powerful.
§ 321. Pharmaceutical Preparations.—The percentage of coniine in the plant itself, and in pharmaceutical preparations, can be approximately determined by distilling the coniine over, in a partial vacuum,[344] and titrating the distillate with Mayer’s reagent, each c.c. = about ·00416 grm. of coniine. It appears to be necessary to add powdered potassic chloride and a small quantity of diluted sulphuric acid before titrating, or the precipitate does not separate. In any case, the end of the reaction is difficult to observe.[345]
[344] This is easily effected by uniting a flask containing the alkaloidal fluid, air-tight, with a Liebig’s condenser and a receiver, the latter being connected with Bunsen’s water-pump, or one of the numerous exhausting apparatuses now in use in every laboratory.
[345] Dragendorff, Die Chemische Werthbestimmung einiger starkwirkender Droguen, St. Petersb., 1874.
The fresh plant is said to contain from about ·04 to ·09 per cent., and the fruit about 0·7 per cent. of coniine.
The officinal preparations are—the leaves, the fruit, a tincture of the fruit, an extract of the leaves, the juice of the leaves (Succus conii), a compound hemlock pill (composed of extract of hemlock, ipecacuanha, and treacle), an inhalation of coniine (Vapor conii), and a poultice (Cataplasma conii) made with the leaves.