MERCURY
Metallic mercury possesses no toxicological interest, as it appears to be almost inert, even in very large doses. If applied to the skin in a finely-divided state, as in mercurial ointment, or internally, as blue pill, its toxic effects may be produced. The vapour given off from the metal is highly poisonous, producing salivation, emaciation, and death. A singular accident of poisoning by mercurial vapour occurred on board H.M.S. Triumph in 1810, owing to the bursting of bladders containing large quantities of the metal; in three weeks 200 men were affected with salivation, etc., nearly all the cattle on board died, as well as the mice, a dog, and a canary-bird.
Fig. 34.—Photo-micrograph of crystals of corrosive sublimate, × 50.
(R. J. M. Buchanan.)
Corrosive Sublimate
This is the most important of the preparations of mercury. It occurs either in crystalline masses of prismatic crystals or as a white powder. It is now known among chemists as the perchloride, though it is frequently spoken of as the bichloride, chloride, and oxymuriate of mercury. It has a powerful metallic and styptic taste, and is soluble in about sixteen parts of cold water and three of boiling water. Alcohol and ether readily dissolve it, the latter having the power of abstracting it from its solution in water. This property of ether is of importance as a means of separating corrosive sublimate from its solution in other liquids. It is important to remember that corrosive sublimate is soluble in alcohol (R. v. Walsh). The liquor hydrargyri perchloridi of the Pharmacopœia contains half a grain of the salt to a fluid ounce of water. Half a grain of the muriate of ammonia is added to increase the solubility of the mercurial salt. Applied externally to the unbroken skin, corrosive sublimate has caused death in several cases, the symptoms being almost identical with those which follow the entrance of the poison into the stomach. Toxic symptoms have followed intra-uterine or vaginal injections of solution of perchloride of mercury, also when it has been used to wash out abscess cavities. Acute poisoning, in some cases fatal, has resulted from the external application of corrosive sublimate to ulcers and tumours.
Symptoms of Poisoning by
Corrosive Sublimate
Acute.—The symptoms come on almost immediately the poison is swallowed. A strong metallic coppery taste in the mouth is experienced, and a choking sensation in the throat. Pain of a burning character is felt, extending from the mouth to the stomach, followed by nausea and vomiting of stringent mucus, more or less tinged with blood, and violent purging, the evacuations being also mixed with blood and mucus. The pulse is feeble, quick, and irregular; the countenance flushed or pale, and the tongue white and shrivelled. This appearance of the tongue is not present in all cases. Broncho pneumonia may occur. The skin is cold and clammy, and the functions of the kidneys are altered and albuminuria present, there being in many cases complete suppression of urine. As is the case with other irritant poisons, the symptoms and effects produced admit of considerable variation. Thus, there may be no pain in the stomach, and no purging. Salivation is present in some cases, but chiefly in those in whom the fatal termination is somewhat prolonged. This sign is not infrequently absent. Poisoning with corrosive sublimate differs from arsenical poisoning in the following particulars:—Corrosive sublimate has a distinct metallic taste, arsenic is almost tasteless; the symptoms in the former supervene immediately the poison is swallowed, in the latter there is a short delay. The discharges in corrosive sublimate are more frequently bloody than in arsenic poisoning.
Chronic.—The symptoms present in this form of poisoning are modified by the size of the dose, and the interval allowed to elapse between each dose. Nausea, followed by occasional vomiting, and pains in the stomach, are complained of by the patient. There is general constitutional disturbance, with anæmia and cachexia, and consequent mental depression. Salivation, as might be expected, is a more prominent symptom than in acute poisoning; but the salivation may be intermittent—that is, it may cease and then reappear, even after the lapse of months, without an additional dose of mercury having been given in the interval. Salivation may also come on in the course of certain diseases, attacking the salivary glands, and it may also be produced by other causes—pregnancy, etc. The glands of the mouth become swollen and painful, the gums tender, and the teeth loosened fall out of the mouth. Periostitis of the jaw may occur. The breath has a peculiar, offensive smell, the bowels are irritable, and diarrhœa is not infrequently present. It must be borne in mind that in certain diseases—granular disease of the kidney—the smallest dose of any mercurial preparation may produce profuse ptyalism. And the toxicologist must be careful not to mistake the affection known as cancrum oris, or “the canker,” most common in delicate, ill-fed children and adults, for the effects of mercury. The nervous system is more or less affected, neuralgic pains and mercurial tremors being present in many cases. The tremors commence in the tongue and face and spread to the arms and legs—they are similar to those of paralysis agitans; at first they are invoked by exertion, finally they become continuous; they cease during sleep. Paralysis may also occur, especially in those exposed to the vapour of mercury. Habit appears to exert some influence on the action of corrosive sublimate, if we may accept the story of the old man of Constantinople, who for thirty years took large doses till his daily allowance was a drachm, and then died at the respectable age of one hundred years.
Post-mortem Appearances.—The morbid appearances are chiefly confined, as is the case with arsenic, to the stomach and bowels; but the corrosive action of the mercurial sublimate is more marked. Inflammation more or less intense is always present in the stomach, the mucous membrane of which may be found of a slate-grey colour, corroded, and so soft as to scarcely admit of the removal of the organ without tearing it. The cæcum and rectum are also sometimes found inflamed, and the mucous membrane softened. Perforation of the stomach is very rare, only one case having been recorded in which this was present. The mouth, throat, and gullet may also present signs of the action of the poison similar to those just described as seen in the stomach. Patches of pneumonia are present in the lungs of some cases, and the kidneys show coagulative and desquamative nephritis.
Fatal Dose.—The smallest dose was two grains in the case of a child, but the exact amount to cause death in an adult has not been accurately determined. Recovery has taken place after one hundred grains has been taken.
Fatal Period.—From half an hour to five days. No exact time can be stated. In one case death took place on the twelfth day after swallowing seventy grains of the perchloride.
Treatment.—Vomiting, if present, must be encouraged; if absent, it must be produced by emetics—zinc sulphate or cupric sulphate, followed by copious draughts of warm water. The hypodermic injection of ¹/₂₀ to ⅒ grain of apomorphine may also be used to produce vomiting. Albumen, the white of egg, or vegetable gluten produced from flour by washing it in a muslin bag, should be given. The albuminate of mercury so formed should be quickly removed by an emetic or lavage by means of a soft tube and funnel in mild cases, as it is soluble in excess of albumen, and may be digested or absorbed. The rapid removal of the poison from the stomach, however, is the end to which all our exertions must tend. The forcible use of the stomach pump should not be employed if it can possibly be avoided, as it may greatly injure the softened mucous membrane of the gullet and stomach. Opium may be given to relieve pain, and opium enemata to relieve purging and tenesmus.
Calomel
Calomel, or the subchloride of mercury, is not used as a poison. In large doses it may act as an irritant poison, and death has not infrequently occurred even from comparatively small doses. Profuse salivation and gangrene of the mouth have resulted from its use, and cases are recorded of death resulting from these. In many cases idiosyncrasy appears to modify, more or less, the action of this preparation of mercury. The poisonous effect of calomel has been attributed to—(1) Adulteration with corrosive sublimate. (2) Conversion of the calomel into corrosive sublimate by the action of the hydrochloric acid of the gastric juice.
N.B.—The free acid of the gastric juice is probably in too small a quantity to materially alter the composition of the calomel.
Ammonio-Chloride of Mercury
White precipitate may, if taken in large doses, produce alarming effects, but it cannot be regarded as an active poison. Pavy‘s experiments on rabbits indicate that it is a more powerful poison than was formerly thought to be the case. Its action is that of an irritant, accompanied with, in some cases, severe salivation.
Red Precipitate
Red oxide of mercury possesses poisonous properties, but it is seldom employed as a poison. The symptoms most frequently present are vomiting, coldness of the surface of the body, stupor, pain in the abdomen, and cramps of the muscles of the lower extremities. The vomited matters are generally mixed with some of the red oxide.
Cinnabar. Vermilion
A compound of sulphur and mercury in the form of a dark red crystalline mass is known as cinnabar; and to the same substance reduced to a fine powder the name vermilion has been given. It is used as a red pigment. It can scarcely be considered as a poison, Orfila asserting that it is not poisonous. The vapour of this substance appears, however, to be capable of producing severe symptoms, and in one case, profuse salivation resulted from the application of the vapour to the body.
Cyanide of Mercury
This substance, though an active poison little inferior to corrosive sublimate, is seldom used as such, probably from its being better known to chemists than to the general public. It differs from corrosive sublimate in having no local corrosive action. It has been supposed, but proof is wanting, that its injurious effects are due to its decomposition by the acids of the stomach and the formation of prussic acid. Death has occurred in nine days from a dose of ten grains. It acts as an irritant. The sulphocyanide of mercury is used in the manufacture of the toy known as Pharaoh‘s serpents.
Turbith Mineral
A powerful irritant poison, but seldom used. A drachm has caused death in a boy sixteen years of age. Coldness of the surface, burning pain in the stomach and bowels, with other symptoms of irritant poisoning, were present. After death, the mucous membranes of the throat, stomach, and bowels were found considerably inflamed.
Nitrates of Mercury
These substances—the nitrate and sub-nitrate—are used in the arts for various purposes. They act as powerful irritant poisons, with symptoms and post-mortem appearances not unlike those before described when speaking of corrosive sublimate and other irritants.
Chemical Analysis:
Table showing the Reaction of Mercuric and
Mercurous Salts with Reagents
Detection of Mercury in the Tissues and
in the Contents of the Stomach.
Mercury is particularly liable to be absorbed by the tissues; it also readily combines with various organic substances, gelatine, albumin, &c.
Fig. 35.—Photo-micrograph of globules of
mercury obtained by Reinsch‘s process, × 50.
(R. J. M. Buchanan.)
A.—If the contents of the stomach are under examination, they should be diluted with distilled water, filtered, and the residue pressed and reserved for further examination.
The liquid thus obtained may be concentrated, and, while still warm, slightly acidified with hydrochloric acid. A slip of zinc foil, with a piece of gold foil twisted round it, is then introduced. If mercury be present, the gold will, sooner or later, lose its yellow colour, and its surface become white and silvery, while the zinc is wholly or partially dissolved. The gold being removed, separated from the zinc, washed first with water and then with ether, is divided into two equal parts. One half may be heated in a reduction tube, when it will yield a sublimate of metallic mercury, identified by the spherical form of the globules under a magnifying-glass, and their metallic reflection and complete opacity. The other half of the gold may be treated with nitric acid and heated, which will dissolve off the mercury. The resulting solution, after expelling the excess of acid by evaporation, will give a scarlet precipitate with iodide of potassium soluble in excess; and, with protochloride of tin, a black precipitate of metallic mercury.
B.—For the detection of mercury in the insoluble form, the residue from A is dried; or, if the tissues are under examination, they should be finely divided, and freed from superfluous moisture. In either case, the substance is boiled in moderately strong nitric or hydrochloric acid (about one part of acid to four of water). After digestion for some time, the liquid is filtered, concentrated, and tested as in A. When there is reason to infer the presence of corrosive sublimate in considerable quantity in an organic liquid, advantage may be taken of the solubility of the salt in ether, and the power possessed by this liquid of abstracting it from its aqueous solutions. The liquid is agitated with an equal volume of ether, the ethereal solution poured off and allowed to spontaneously evaporate, when the corrosive sublimate will be left in white silky prisms, yielding all the characteristic reactions of the salt. In obscure cases of salivation, the saliva should be examined as follows: Take about two drachms of the saliva, acidulate with pure hydrochloric acid, and immerse in the mixture a very small piece of copper gauze attached to a platinum wire, and set aside in a warm place for some hours. If mercury be present, the copper will be covered with a white coating; this should be washed and heated in a reduction tube, when globules of mercury will be formed, and examined with a lens.
C.—Mercury in solution may be detected by Reinsch‘s process. On boiling with pure copper foil after acidifying the solution with hydrochloric acid, the mercury is deposited on the copper in the metallic state, as a whitish silvery film, which can be polished to a silvery mirror surface. On washing the film in water, ether, and absolute alcohol and allowing it to dry, then subliming it in a reduction tube by the aid of heat, the mercury deposits on the cool part of the tube in the form of minute globules, which may be easily recognised through the microscope. If a small crystal of iodine be now placed in the tube and gently warmed so as to volatilise it, but not the mercury, and the tube be left to stand for a short time, the iodine combines with the mercury to form the scarlet iodide, the colour of which renders it easy of recognition.
According to Bonnewyn, the presence of an extremely small quantity of corrosive sublimate (¹/₅₀₀₀₀) in calomel may be detected by immersing a clean knife blade, moistened with alcohol or ether, in the suspected calomel. A black spot is formed on the steel very difficult of removal. No spot is formed when the calomel is pure.