Picrotoxin crystallises out of water, and also out of alcohol, in colourless, flexible, four-sided prisms, often arborescent, and possessing a silky lustre. They are unalterable in the air, soluble in 150 parts of cold, and 25 parts of boiling water, dissolving easily in acidified water, in spirit, in ether, in amyl alcohol, and chloroform. They are without smell, but have an extremely bitter taste. Caustic ammonia is also a solvent.
The crystals are neutral in reaction. They melt at 192°-200° C. to a yellow mass; at higher temperatures giving off an acid vapour, with a caramel-like odour, and lastly carbonising. Picrotoxin in cold concentrated sulphuric acid dissolves with the production of a beautiful gold-yellow to saffron-yellow colour, which becomes on the addition of a trace of potassic bichromate, violet passing into brown. An alcoholic solution turns a ray of polarised light to the left [α]D = -28·1°.
Picrotoxin behaves towards strong bases like a weak acid. Its compounds with the alkalies and alkaline earths are gummy and not easily obtained pure. Compounds with quinine, cinchonine, morphine, strychnine, and brucine can be obtained in the crystalline condition. Dilute sulphuric acid transforms it, with assimilation of water, into a weak gummy-like acid, which corresponds to the formula C12H16O6. Nitric acid oxidises it to oxalic acid. Nitropicrotoxin and bromopicrotoxin, C30H33(NO2)O13, and C30H32Br2O13, can by appropriate treatment be obtained.
Concentrated aqueous solutions of alkalies and ammonia decompose picrotoxin fully on warming. It reduces alkaline copper solution, and colours bichromate of potash a beautiful green. The best test for its presence is, however, as follows:—The supposed picrotoxin is carefully dried, and mixed with thrice its bulk of saltpetre, the mixture moistened with sulphuric acid, and then decomposed with soda-lye in excess, when there is produced a transitory brick-red colour. For the reaction to succeed, the picrotoxin should be tolerably pure.
Solutions of picrotoxin are not precipitated by the chlorides of platinum, mercury, and gold, iodide of potassium, ferro- and ferri-cyanides of potassium, nor by picric nor tannic acids.
§ 590. Fatal Dose.—Vossler killed a cat in two hours with a dose of ·12 grm. (1·8 grain); and another cat, with the same dose, died in 45 minutes. Falck destroyed a young hound with ·06 grm. (·92 grain) in 24 to 26 minutes. Given by subcutaneous or intravenous injection, it is, as might be expected, still more lethal and rapid in its effects. In an experiment of Falck’s, ·03 grm. (·46 grain), injected into a vein, destroyed a strong hound within 20 minutes; ·016 grm. (·24 grain) injected under the skin, killed a guinea-pig in 22 minutes; and ·012 grm. (·18 grain) a hare in 40 minutes. Hence it may be inferred that from 2 to 3 grains (12·9 to 19·4 centigrms.) would in all probability, be a dangerous dose for an adult person.
§ 591. Effects on Animals.—The toxic action of picrotoxin on fish and frogs has been proposed as a test. The symptoms observed in fish are mainly as follows:—The fish, according to the dose, show uncertain motions of the body, lose their balance, and finally float to the surface, lying on one side, with frequent opening of the mouth and gill-covers. These symptoms are, however, in no way distinguishable from those induced by any poisonous substance in the water, or by many diseases to which fish are liable. Nevertheless, it may be conceded that in certain cases the test may be valuable—if, e.g., beer be the matter of research, none of the methods used for the extraction of picrotoxin will be likely to extract any other substance having the poisonous action described on fish, so that, as a confirmatory test, this may be of use.
Frogs, under the influence of picrotoxin, become first uneasy and restless, and then somewhat somnolent; but after a short time tetanic convulsions set in, which might lead the inexperienced to imagine that the animal was poisoned by strychnine. There is, however, one marked distinction between the two—viz., that in picrotoxin poisoning an extraordinary swelling of the abdomen has been observed, a symptom which, so far as known, is due to picrotoxin alone. The frog is, therefore, in this instance, the most suitable object for physiological tests.
Beer extract containing picrotoxin is fatal to flies; but no definite conclusion can be drawn from this, since many bitter principles (notably quassia) are in a similar manner fatal to insect life.