There are two nitrates, the protonitrate and pernitrate. 1. The protonitrate is in transparent colourless crystals, entirely soluble in water with the aid of a slight excess of nitric acid; and the solution is precipitated black by the alkalis, black by sulphuretted-hydrogen, white by muriatic acid, and yellow by hydriodate of potass. The crystals when heated discharge fumes of nitrous acid, and when the whole acid is driven off the red oxide is left, which by farther heat is converted into metallic mercury. 2. The pernitrate is similarly affected by heat. Its crystals form white or yellowish needles. Water decomposes them, separating an insoluble yellowish subnitrate, and dissolving a supernitrate, which is precipitated yellow by the alkalis, black by sulphuretted-hydrogen, carmine-red by the hydriodate of potass. Copper separates mercury from both nitrates; and so does gold or platinum when aided by a galvanic current.
Section II.—Of the mode of Action of Mercury and the Symptoms it excites in Man.
The effects of mercury on the animal body are more diversified than those of any other poison. It acts on a great number of important organs, and in consequence the phenomena of its action are proportionately various. It is not surprising, therefore, that some ambiguity still prevails as to its mode of action and the circumstances by which the action is regulated.
The attention of toxicologists in their physiological researches has been chiefly turned to the more active preparations of mercury, and especially to corrosive sublimate, when given in such quantity as to prove fatal in a few days at farthest. The more immediate and prominent properties of corrosive sublimate have consequently received some elucidation. But its qualities as a slow poison, as well as the analogous operation of the less active compounds of mercury, have not been experimentally examined with the same care: indeed it is questionable whether the phenomena of the latter description as they occur in man can be studied with much advantage by means of experiments on animals.—In treating of the mode in which the compounds of mercury act, the most convenient method will be to consider at present its action in the form of corrosive sublimate in large doses as ascertained by late experiments, and to reserve the consideration of the general action of mercurial poisons at large till their effects on man have been fully described.
The mode of action of corrosive sublimate has been examined particularly by Sir B. Brodie in 1812;[[853]] by Dr. Campbell in 1813,[[854]] by M. Smith in 1815,[[855]] by M. Gaspard in 1821,[[856]] and more lately by Professor Orfila.[[857]] The following is a short analysis of their experiments and results.
The leading phenomena remarked by Sir B. Brodie, on large doses being introduced into the stomach, were very rapid death, corrosion of the stomach, and paralysis of the heart. In rabbits and cats, from six to twenty grains, injected in a state of solution into the stomach, produced in a few minutes insensibility and laborious breathing, then convulsions, and death immediately afterwards,—the whole duration of the poisoning varying from five to twenty-five minutes. After death the inner membrane of the stomach was gray, brittle, and here and there pulpy,—changes precisely the same with those produced by corrosive sublimate on the dead stomach. When the chest was opened immediately after death, the heart was found either motionless or contracting feebly; and in both circumstances the blood in its left cavities was arterial.
These experiments make it evident that the brain was acted on as well as the heart, and that the immediate cause of death was stoppage of the heart’s action. But they do not show whether the action takes place through absorption, or by a primary nervous impression transmitted along the nerves.
I am not acquainted with any other experiments of consequence on the operation of corrosive sublimate when introduced into the alimentary canal. But some interesting observations have been made by Campbell, Smith, Gaspard, and Orfila severally as to its effects when applied to the cellular tissue or injected at once into the blood of a vein. It follows from their researches, taken along with those of Sir B. Brodie, that, like arsenic, corrosive sublimate is an active poison, to whatever part or tissue in the body it is applied.
Campbell, Smith, and Orfila all agree in assigning to it dangerous properties, when it is applied to a wound or the cellular tissue of animals. Even in the solid state, and in the dose of three, four, or five grains only, it causes death in the course of the second, third, fourth, or fifth day. The symptoms antecedent to death are generally those of dysentery; and corresponding appearances are found after death, namely, redness, blackness, or even ulceration of the villous coat of the stomach and rectum, the intermediate part of the alimentary canal being sound. This poison, therefore, has, like arsenic, the singular power of inflaming the stomach and intestines, even when it is introduced into the system through a wound.
But this is not its only property in such circumstances. According to Smith and Orfila, it also possesses the power of inflaming both the lungs and the heart. Orfila found the lungs unusually compact and œdematous in some parts; and Smith observed on their anterior surface black spots, elevated in the centre, evidently the consequence of effusion of blood. As to the heart, in one of Smith’s experiments black spots were found in its substance, immediately beneath the lining membrane of the ventricles; and Orfila invariably found in one part or another of the lining membrane, most commonly on the valves, little spots of a cherry-red or almost black colour; nay, on one occasion he observed these spots so soft that slight friction made little cavities. The production of pneumonia by corrosive sublimate when applied to a wound appears well established; but the appearances assumed as indications of carditis are equivocal, since they may have arisen simply from dyeing of the membrane of the heart in the fluid part of the blood after death.