Of the preparations of mercury, corrosive sublimate is the most important to the toxicologist; for although they all possess in a greater or less degree poisonous properties, yet the instances in which the other compounds have been used to destroy life are extremely rare. The treatment in all cases must be the same. It is worthy of remark that mercury, whilst in the metallic state, is destitute of injurious properties, but if oxidized or otherwise rendered fit for absorption, it may give rise to dangerous symptoms. Thus, workers in mercurial mines suffer much, as did those who were employed in silvering looking-glasses by the old process. Large doses (from half a pound to two pounds) have been given in obstinate cases of constipation, intussusception, &c., without any remarkable effect.

Corrosive Sublimate (Oxymuriate of Mercury, Chloride of Mercury, Bichloride of Mercury).—This preparation of Mercury, which, more strictly speaking, belongs, like the chlorides of zinc and antimony, to the class Corrosives, is usually met with in the form of imperfect crystalline masses, or as a white powder. It has an acrid, coppery taste, so powerful that but little could be swallowed without the individual becoming aware of it. It is very soluble in water. Three grains is the smallest quantity that has been known to prove fatal; and from this to five grains may probably be stated as the average dose necessary to destroy life. Recovery has taken place after as much as eighty grains had been swallowed. Death has occurred in less than half an hour; while, in some instances, life has been maintained until the sixth day, and in one instance (where between three and four scruples had been swallowed) until the twelfth day. It is probable that the average duration of fatal cases is from twenty-four to thirty-six hours.

Symptoms.—In the majority of cases the symptoms commence immediately, with an acrid metallic taste, often described as coppery, and a sense of constriction and burning heat in the throat and stomach. The burning pain gradually extends over the abdomen, and is much increased by pressure. There is nausea, with vomiting of the contents of the stomach. These matters are sometimes mixed with blood and stringy masses of mucus. The sickness is accompanied by diarrhoea or dysentery, swelling of the abdomen, and increased pain. The countenance becomes flushed and often swollen, though it is occasionally pallid and anxious; the lips and tongue get white and shrivelled; there is frequently some dyspnoea, while the pulse is small, or wiry and frequent; and death is preceded by faintness, cramps, insensibility, or convulsions.

Should these effects not prove rapidly fatal, the pain will gradually become lessened, though attacks of colic and nausea may come on at intervals for several days. Often the secretion of urine is almost, or even quite, suppressed. After a time there are symptoms of hectic fever, with much depression. The gums and salivary glands also become swollen, there is a coppery taste in the mouth, the breath is very foetid, and there is severe ptyalism or salivation. This latter effect is the most prominent feature in the chronic form of poisoning, where small and frequently-repeated doses have been given: it often proceeds to such an extent as to cause death, when the patient would otherwise probably recover.

It must not be forgotten that salivation sometimes arises where no mercurial of any kind has been given. Thus arsenic, bismuth, lead, iodide of potassium, opium, &c., may induce it in some very peculiar constitutions. Small medicinal doses (as a few grains of calomel) may also excite it in certain susceptible individuals; and especially in persons suffering from renal disease. It may also occur spontaneously, as in stomatitis or inflammation of the mouth; and very troublesome examples of it may occur in pregnant women.

It is strange that neither in acute nor chronic mercurial poisoning do we observe any marked loss of muscular power. Yet workers in quicksilver (owing to the absorption of the fumes of mercury during respiration) are very apt to suffer from a peculiar kind of paralysis; which commences with inability to direct the hands and arms, and goes on to a shaking or trembling of all parts of the body.

Post-mortem Appearances.—The appearances produced by corrosive sublimate are confined chiefly to the digestive canal. The mucous membrane of the mouth, fauces, and oesophagus is softened and of a whitish or bluish-grey color. The stomach also presents marks of violent inflammation; beneath the mucous membrane numerous patches of extravasated blood are seen, and frequently corrosion or ulceration has been found. The large and small intestines, the peritoneum, and especially the urinary organs, often appear inflamed. In many instances the bladder has been much contracted.

Treatment.—This must consist in the removal of the poison and the administration of antidotes. Vomiting is best promoted by administering copious draughts of fluids containing albumen: but if necessary ipecacuan may be given. The white and the yolk of raw eggs with milk should be abundantly administered. Gluten has been much recommended, and may readily be prepared by washing flour in a muslin bag under a stream of water; but on an emergency it will be best to exhibit the flour at once, made into a paste with milk or water. The free use of demulcent drinks, milk, and ice will be very grateful to the patient’s feelings. Gargles of alum or borax do some good. Opiates may be given in small doses, if there be much pain, and we should allow only a milk or farinaceous diet. Sucking chlorate of potash has been recommended to check the salivation. The most useful remedy, however, is the iodide of potassium; for this salt destroys the compounds formed by the union of mercury with certain of the tissues, and eliminates the poison through the kidneys.

Tests.—Corrosive sublimate is completely volatilized by heat.

1. Liquor potassÆ added to its solution gives a yellow precipitate. This precipitate, if washed, dried, and heated in a test tube, gives a ring of metallic mercury in the form of globules in the cool part of the tube. In like fashion corrosive sublimate itself may be reduced and volatilized if heated with black flux.

2. On adding a solution of iodide of potassium to a small quantity of the solution, a bright scarlet precipitate, soluble in excess of iodide of potassium, is produced.

3. If a drop or two of a solution of corrosive sublimate, slightly acidulated with hydrochloric acid, be placed on a sovereign, and the solution and the gold be touched with a piece of zinc or an iron key, the mercury will be deposited as a bright silvery stain on the gold.

Calomel (Subchloride or Chloride of Mercury) is a heavy white powder, which is usually regarded as a safe medicine. Yet, in some peculiar constitutions, it has caused excessive salivation and death, even though only a few grains have been given. In large doses it may be regarded as an irritant poison. It is distinguished from corrosive sublimate by forming a black precipitate with caustic potash and by its insolubility in water.

Ammonio Chloride of Mercury (White Precipitate).—This substance is a chalky looking powder, containing about eighty per cent. of mercury. It produces vomiting, purging, great pain in the stomach, cramps, and convulsions. Out of fourteen cases, collected by Dr. Taylor, in which from a few to forty grains were taken, only two proved fatal.

The remaining preparations of mercury, which in rare instances have been used as poisons, are the Red Oxide of Mercury (red precipitate); the Red Sulphuret of Mercury (cinnabar or vermilion); the Cyanide of Mercury; the Nitrates of Mercury; and Turpeth Mineral.

Mercury may be separated from organic admixture by Reinsch’s method.