5. It is united with alimentary substances which have effected its decomposition. It has been frequently stated during the course of the present inquiry, that corrosive sublimate is easily susceptible of decomposition, and that various alimentary substances, of animal as well as vegetable origin, have the power of converting it into calomel.[[289]] This important fact was first noticed by Chaussier[[290]] and has been more fully investigated and confirmed by Orfila.[[291]] Where the quantity of mercurial salt has been considerable, we may generally obtain, on washing the alimentary matter, a sufficient portion for experiment; but where the dose has been small, or where it has been ejected by frequent vomiting, the whole residue may be decomposed; in which case we must seek to establish the fact of poisoning, through the detection of metallic mercury, by the processes of calcination and sublimation.
6. It is decomposed, and a part exists in intimate combination with the membranes of the alimentary canal. If all the preceding experiments have failed in detecting the presence of corrosive sublimate, it becomes our duty to examine the textures with which it may be supposed to have come in contact; the coats of the canal should be cut into pieces, and calcined with potass, when, if they have been acted upon by sublimate, they will yield metallic mercury by sublimation. “The alimentary canal,” says M. Orfila, “acts upon the sublimate like all other animal substances; muriatic acid is disengaged, and muriate of mercury ad minimum (calomel) is formed, which combines with the substance of the viscus.
It may be objected,” continues this distinguished experimentalist, “that this chemical action does not take place in the living animal; that our texture, while endued with the vital principle, is not subservient to the same laws as inorganic substances: I am not ignorant of the extent to which this objection is well-founded; but admitting the justice of it, the conclusion is not less true, that if the stomach contains corrosive sublimate at the moment of death, this body will, from that moment, act on the texture of the viscus itself. If the stomach contain a large quantity of aliment, the effects of such an action may be scarcely perceptible; but on the contrary, they will be easily applicable, should the viscus be empty, and especially if the examination of the body takes place several days after death.”[[292]]
In conducting experiments upon this, and indeed all other mineral poisons, the chemist must be prepared to meet with anomalies depending upon the impurities or adulterations of the substance under examination.
Red Oxide of Mercury. Precipitate per se.
We are not aware of any instance of death having, from accident or design, taken place in consequence of the administration of this substance; indeed its red colour, insolubility in water, and comparative rarity, will protect mankind sufficiently against mistake, and at the same time render its secret administration extremely difficult. It is, moreover, mild in its effects, unless in large doses, or, under particular circumstances of constitution. It may be identified by its form, which is that of minute crystalline scales, of a deep red colour, and by exposing it to heat in a glass tube, by which it undergoes decomposition, giving out metallic mercury, adhering to the sides of the tube, and oxygen gas, which is disengaged.
Red Precipitate, or Nitric Oxide of Mercury.
This is, strictly speaking, a sub-nitrate of mercury, and is much more poisonous than the preceding substance. Plouquet[[293]] relates the case of a man, who swallowed by accident some red precipitate, when he immediately experienced violent colics, copious vomitings, a trembling of his limbs, and cold sweats. Its external characters will at once enable the chemist to identify it.
Other Preparations of Mercury.
The various saline compounds of this metal, as the acetate, sulphate, and nitrate, are all highly poisonous, but they do not appear to us to merit a separate consideration; and more especially as we have already explained the various processes by which every variety of preparation may be identified. We may just remark that the sulphuret, better known by the name of cinnabar, or vermilion, has been known to occasion deleterious effects. Dr. Gordon Smith[[294]] states, upon the authority of Mr. Accum,[[295]] that “Vermilion has been detected as a poisonous ingredient in cheese:” this may be very true, but he should have stated at the same time, that the deleterious effects produced by it, did not arise from the mercurial sulphuret, but from the red lead with which it happened to be adulterated; and it is necessary to acquaint the forensic chemist, that such a fraud[[296]] is by no means uncommon; it may be very easily detected by burning a small portion of the suspected sample on a piece of bread in the candle, when metallic globules will announce the presence of lead; for the oxide of mercury, although revived by the process, will at the same time be volatilized. The bread by combustion affords the carbon by which the metallic reduction is effected.