PART IX.—INORGANIC POISONS. (continued 3)

There is also recorded[842] an outbreak of lead-poisoning among 150 men of the 7th Infantry at Tione, in the Southern Tyrol. One case proved fatal, forty-five required treatment in hospital. The symptoms were pallor, a blue line in the gums, metallic taste in the mouth, a peculiar odour of the breath, a loaded tongue with a bluish tint, obstinate constipation with loss of appetite whilst all complained, in addition, of dragging of the limbs and of the muscles of the chest, and difficulty of breathing. In the severer cases there were tetanic spasms, muscular tremors, and anæsthesia of the fingers and toes. The pulse and temperature were normal, save in a few cases in which there were fever and sweats at night. In none was there colic, but the constipation was obstinate. In two of the worst cases there was strangury. Acute cases occur occasionally from poisoning by the carbonate of lead. Dr. Snow recorded an instance (in 1844) of a child who had eaten a piece as big as a marble, ground up with oil. For three days the child suffered from pain in the abdomen and vomiting, and died ninety hours after taking the poison. In another case, in which a young man took from 19 to 20 grms. of lead carbonate in mistake for chalk as a remedy for heartburn, the symptoms of vomiting, pain in the stomach, &c., commenced after a few hours; but, under treatment with magnesic sulphate, he recovered.

The chromate of lead is still more poisonous (see Art. “Chromium”).

§ 782. Chronic Poisoning by Lead.—Chronic poisoning by lead—often caused by strange and unsuspected channels, more frequently an incident, nay, almost a necessity, of certain trades, and occasionally induced by a cunning criminal for the purpose of simulating natural disease—is of great toxicological and hygienic importance. In the white-lead trade it is, as might be expected, most frequently witnessed; but also in all occupations which involve the daily use of lead in almost any shape. The chief signs of chronic poisoning are those of general ill-health; the digestion is disturbed, the appetite lessened, the bowels obstinately confined, the skin assumes a peculiar yellowish hue, and sometimes the sufferer is jaundiced. The gums show a black line from two to three lines in breadth, which microscopical examination and chemical tests alike show to be composed of sulphide of lead; occasionally the teeth turn black.[843] The pulse is slow, and all secretions are diminished. Pregnant women have a tendency to abort. There are also special symptoms, one of the most prominent of which is often lead colic.

In 142 cases of lead-poisoning, treated between 1852 and 1862 at the Jacob’s Hospital, Leipzig, forty-four patients (or about 31 per cent.) suffered from colic. Arthralgia—that is, pains in the joints—is also very common; it seldom occurs alone, but in combination with other symptoms. Thus, in seventy-five cases of lead-arthralgia treated at Jacob’s Hospital, in only seven were pain in the joints without other complications, fifty-six being accompanied by colic, five by paralysis, and seven by other affections of the nervous system. The total percentage of cases of lead-poisoning, in which arthralgia occurs, varies from 32 to 57 per cent.

Paralysis, in some form or other, Tanqueril[844] found in 5 to 8 per cent. of the cases, and noticed that it occurred as early as the third day after working in lead. The muscles affected are usually those of the upper extremity, then the legs, and still more rarely the muscles of the trunk. It is only exceptionally that the paralysis extends over an entire limb; it more usually affects a muscular group, or even a single muscle. Its common seat is the extensors of the hand and fingers; hence the expression “dropped-wrist,” for the hands droop, and occasionally the triceps and the deltoid are affected. The paralysis is usually symmetrical on both sides. Although the extensors are affected most, the flexors nearly always participate, and a careful investigation will show that they are weakened. If the paralysis continues, there is a wasting and degeneration of the muscle, but this is seen in paralysis from any cause. The muscular affection may cause deformities in the hands, shoulders, &c. Anæsthesia of portions of the skin is generally present in a greater or less degree. A complete analgesia affecting the whole body has been noticed to such an extent that there was absolute insensibility to burns or punctures; but it is usually confined to the right half of the body, and is especially intense in the right hand and wrist.

§ 783. The older writers recognised the toxic effect of lead on the nervous system. Thus Dioscorides speaks of delirium produced by lead, Aretaeus of epilepsy, and Paul of Ægina refers to it as a factor of epilepsy and convulsions. But in 1830, Tanqueril first definitely described the production of a mental disease, which he called “lead encephalopathy.” This he divided into four forms—(1) a delirious form; (2) a comatose; (3) a convulsive; and (4) a combined form, comprising the delirious, convulsive, and comatose. Dr. Henry Rayner,[845] and a few other English alienists, have directed their attention to this question; and, according to Dr. Rayner’s researches, the number of male patients admitted into Hanwell Asylum, engaged in trades such as plumbing, painting, and the like, is larger in proportion to the number admitted from other trades than it should be, compared with the proportion of the various trades in the county of Middlesex, as ascertained from the census. Putting aside coarse lead-poisoning, which may occasionally produce acute mania, the insanity produced by prolonged minute lead intoxications possesses some peculiar features. It develops slowly, and in nearly all cases there are illusions of the senses, of hearing, taste, or smell, and especially of sight. Thus, in one of Dr. Rayner’s cases the patient saw round him “wind-bags blown out to look like men,” apparitions which made remarks to him, and generally worried him. Besides this form, there is also another which closely resembles general paralysis, and, in the absence of the history, might be mistaken for it.

§ 784. The degenerative influence on the organ of sight is shown in six of Dr. Robertson’s patients, whose insanity was ascribed to lead—four of the six were either totally or partially blind.

The amaurosis has been known to come on suddenly, and after a very brief exposure to lead, e.g., a man, thirty-four years of age, after working for three days in a white-lead factory, was seized with intense ciliary neuralgia, had pains in his limbs and symptoms of lead-poisoning, and the right eye became amaurotic.[846] This form of impairment or loss of vision is different from the Retinitis albuminurica,[847] which may also be produced as a secondary effect of the poison; the kidneys in such cases being profoundly affected. The kind of diseased kidney produced by lead is the granular contracted kidney.

Eulenberg speaks of the sexual functions being weakened, leading to more or less impotence.

Lewy,[848] in 1186 patients suffering from lead-poisoning, has found caries or necrosis in twenty-two cases, or about 1·8 per cent.; fifteen were carious affections of the upper jaw, four of the fore-arm, two of the thigh, and one of the rib and sternum. Epilepsy and epileptiform convulsions occur in a few cases; it is very possible that the epilepsy may be a result of the uræmic poisoning induced by diseased kidneys.

Five cases of fatal poisoning occurred between 1884-6 among the employés of a certain white-lead factory in the east of London. The cases presented the following common characters. They were all adult women, aged from 18 to 33, and they had worked at the factory for short periods, from three to twelve months. They all exhibited mild symptoms of plumbism, such as a blue line round the gums, and more or less ill-defined indisposition; paralyses were absent. They were all in their usual state of health within a few hours or days preceding death. Death was unexpected, mostly sudden. In four cases it was preceded by epileptic fits and coma; but in the fifth case no convulsions were noted, although they may have occurred in the night.

The author[849] had an opportunity of investigating by chemical means the distribution of lead in the fourth and fifth cases in the liver, kidney, and brain.

In the fourth case, from 402 grms. of liver 24·26 mgrms. of lead sulphate were separated. The right kidney (weighing 81 grms.) yielded 5·42 mgrms. of lead sulphate. The brain was dehydrated with alcohol, and then treated with ether, hot alcohol, and chloroform until an albuminoid residue remained; lead was extracted from each of these portions, viz., the alcohol used for dehydration, the ethereal and chloroform extracts, and the albuminoid residue, as follows:—

Mgrms. of Lead Sulphate.

Soluble in cold alcohol, 1·11

Soluble in ether and chloroform and hot alcohol, 25·47

Albuminoid residue, 7·76

34·34

In the fifth case, the brain was examined more in detail, and the lead present estimated in the following solutions and substances:—

1. Alcohol used for dehydration. This may be called “the watery extract,” for, after the brain has remained in strong alcohol for some weeks, the result is that the alcohol contains much water and substances extracted with water.

2. White matter—(a) from cerebrum; (b) from cerebellum.

3. Kephalin—(a) from cerebrum; (b) from cerebellum.

4. Ether extract, kephalin-free—(a) from cerebrum; (b) from cerebellum.

5. Substances soluble in cold alcohol—(a) from cerebrum; (b) from cerebellum.

6. The albuminoid residue—(a) from cerebrum; (b) from cerebellum.

The general results were as follows:—

Cerebrum, 460·8 grms. Mgrms. of PbSO₄. Cerebellum, 156·2 grms. Mgrms. of PbSO₄

White matter freed from kephalin by ether, 0·0 5·0

Kephalin, 1·5 6·0

Ether extract, kephalin-free, 0·0 0·0

Substances soluble in cold alcohol, 0·0 0·0

Albuminoid residue, 40·0 6·0

41·5 17·0

The aqueous extract contained 1·5 mgrm. of lead sulphate. In neither of the cases did the pathologist ascertain the total weight of the brain, but, presuming that the weight was an average weight, and that the lead in the remainder of the brain was similarly distributed, the amount of lead calculated as sulphate would amount to 117 mgrms. From these results it appears to the author probable that lead forms a substitution compound with some of the organic brain matters. This view would explain the absence of changes apparent to the eye found in so many of the fatal cases of lead encephalopathy.

§ 785. Lead taken for a long time causes the blood to be impregnated with uric acid. In 136 cases of undoubted gout, 18 per cent. of the patients were found to follow lead occupations, and presented signs of lead impregnation.[850]

Ellenberger and Hofmeister[851] found that, with chronic poisoning of sheep with lead, excretion of hippuric acid ceased, and the output of uric acid was diminished. This may be explained by the formation of glycocol being arrested.

§ 786. There are some facts on record which would seem to countenance the belief that disease, primarily caused by an inorganic body like lead, may be transmitted. M. Paul (e.g.) has related the history of the offspring (thirty-two in number) of seven men, who were suffering from lead-poisoning—eleven were prematurely born and one still-born; of the remaining twenty, eight died in the first year, four in the second, and five in the third year, so that of the whole thirty-two, only three survived three years.

The influence of the poison on pregnant women is, indeed, very deleterious. M. Paul noted that in four women who were habitually exposed to the influence of lead, and had fifteen pregnancies, ten terminated by abortion, two by premature confinement, three went the full term, but one of the three children was born dead, a second only lived twenty-four hours; so that, out of the whole fifteen, one only lived fully. In another observation of M. Paul’s, five women had two natural confinements before being exposed to lead. After exposure, the history of the thirty-six pregnancies of these women is as follows:—there were twenty-six abortions (from two to five months), one premature confinement, two infants born dead, and five born alive, four of whom died in the first year.

Chronic poisoning may be nearly always accounted for by the inhaling of lead dust, or by the actual swallowing of some form of lead; but, if we are to accept the fact narrated by the late Dr. Taylor, viz., that he himself had an attack of lead colic from sitting in a room for a few hours daily, in which there was a large canvas covered with white lead and drying oil, and one or two other similar cases,[852] we must allow that there is some subtle volatile organic compound of lead evolved. In the present state of our knowledge, it seems more reasonable to account for such cases by the suggestion that lead has entered the system by an unsuspected channel.

In 1882, a very interesting case occurred at Keighley, in which a mechanic, aged 42, died from the supposed effects of lead-poisoning, induced from drinking the town water, which was proved by Mr. Allen to contain about ³⁄₅ of a grain of lead per gallon. For six months he had been out of health, and a week before his death he suffered from colic, vomiting, constipation, and a blue line round the gums, and occasional epileptiform seizures. After death the kidneys were found granular, and the heart somewhat enlarged. The viscera were submitted to Mr. Allen for analysis; no lead was found in the heart or brain, a slight, non-estimable trace in the kidneys, and about a grain was separated from the liver and spleen. Dr. Tidy, who was called in as an expert, gave a very guarded opinion, rather against the theory of direct lead-poisoning; and the verdict returned by the jury was to the effect that the deceased died from granular kidney, accelerated by lead-poisoning. Murder by the administration of doses of sugar of lead is rare, but such a case has occurred.

At the Central Criminal Court, in December 1882, Louisa Jane Taylor was indicted for poisoning Mary Ann Tregillis at Plumstead, and convicted. From the evidence it appeared that the prisoner, who was thirty-six years of age, came to reside with Mr. and Mrs. Tregillis, an aged couple of eighty-five and eighty-one years respectively. The prisoner was proved to have purchased at different times an ounce and half an ounce of sugar of lead, and to have added a white powder to the medicine of Mrs. Tregillis. The illness of the latter extended from about August 23 to October 23—a period of two months. It is difficult to say when the first dose could have been given, but it was probably some time between August 13 and 23, while the administration, without doubt, ceased on or before October 6, for on that date different nursing arrangements were made. The symptoms observed were nausea, vomiting, pain in the pit of the stomach, burning in the throat, very dark teeth, a blue line round the gums, and slight jaundice. There was great muscular weakness, with trembling of the hands, and a week before death there was paralysis of the right side.

Lead was discovered in most of the viscera, which were in great part normal, but the kidneys were wasted, and the mucous membrane blackened. The actual quantity of lead recovered by analysis was small, viz., 16·2 mgrms. (¹⁄₄ grain) from the liver; from 8 ounces of brain, 3·2 mgrms. (¹⁄₂₀ grain); from half of the stomach, 16·2 mgrms. (¹⁄₄ grain); and from the spleen, the kidneys, and the lungs, small quantities. It is, therefore, probable that, if the whole body had been operated upon, the yield would have been more than ·15 grm. (a little over 2 grains); but then, it must be remembered that the deceased lived, at least, seventeen days after the last dose.

§ 787. Post-mortem Appearances.—In acute cases of poisoning by the acetate, there may sometimes be found a slight inflammatory appearance of the mucous membrane of the stomach and intestines. Orfila considered that streaks of white points adherent to the mucous membrane were pathognomonic; but there have been several cases in which only negative or doubtful signs of inflammatory or other action have presented themselves. A general contraction of the intestines has often been noticed, and is of considerable significance when present; so also is a grey-black mucous membrane caused by deposited lead sulphide. Loen found in dogs and guinea-pigs, poisoned by lead, local inflammation areas in the lungs, liver, and kidneys; but in no case fatty degeneration of the epithelial cells of the liver, kidneys, or intestines. As a rule, no unabsorbed poison will be found in the stomach; the case related by Christison, in which a person died on the third day after taking at a single dose some large quantity of acetate of lead; and at the autopsy a fluid was obtained from the stomach, which had a sweet metallic taste, on evaporation smelt of acetic acid, and from which metallic lead was obtained—is so very extraordinary in every respect, that its entire accuracy is to be questioned. In death from chronic lead-poisoning, there is but little that can be called diagnostic; a granular condition of the kidneys, and all the pathological changes dependent on such a condition, are most frequently seen. If the patient has suffered from colic, a constriction of portions of the intestine has been noticed; also, in cases in which there has been long-standing paralysis of groups of muscles, these muscles are wasted, and possibly degenerated. In instances, again, in which lead has induced gout, the pathological changes dependent upon gout will be prominent. The blue line around the gums, and sometimes a coloration by sulphide of lead of portions of the intestines, may help a proper interpretation of the appearances seen after death; but all who have given any attention to the subject will agree that, simply from pathological evidence, it is impossible to diagnose chronic lead-poisoning.

§ 788. Physiological Action of Lead.—The action of lead is still obscure, but it is considered to have an effect mainly on the nervous centres. The paralysed muscles respond to the direct current, but not to the induced, leading to the suspicion that the intramuscular terminations of the nerves are paralysed, but that the muscular substance itself is unattacked. On the other hand, the restriction of the action to groups of muscles supports the theory of central action.

The lead colic is due to a true spasmodic constriction of the bowel, the exciting cause of which lies in the walls of the bowel itself; the relief given by pressure is explained by the pressure causing an anæmia of the intestinal walls, and thus lessening their sensibility. The slowing of the pulse produced by small doses is explained as due to a stimulation of the inhibitory nerves; and, lastly, many nervous phenomena, such as epilepsy, &c., are in part due to imperfect elimination of the urinary excreta, causing similar conditions to those observed in uræmia.

§ 789. Elimination of Lead.—When a large dose of acetate or carbonate is taken, part is transformed into more or less insoluble compounds—some organic, others inorganic; so that a great portion is not absorbed into the body at all, but passes into the intestines, where, meeting with hydric sulphide, part is changed into sulphide, colouring the alvine evacuations black. Some of the lead which is absorbed is excreted by the kidneys, but the search often yields only traces. Thudichum[853] states that in fourteen cases of lead-poisoning, in two only was obtained a weighable quantity from a day’s urine; in the remaining twelve lead was detected, but only by the brownish colour produced in an acid solution of the ash by hydric sulphide.

The elimination of lead by the kidneys is favoured by certain medicines, such, for example, as potassic iodide. Annuschat found in dogs poisoned by lead from 3·8 to 4·1 mgrms. in 100 c.c. of urine; but, after doses of potassic iodide, the content of lead rose to 6·9 and even to 14 mgrms. Lead appears to be eliminated by the skin, being taken up by the epithelial cells, and minute, insoluble particles coming away with these cells. If a person who has taken small doses of lead for a time be placed in a sulphur water-bath, or have his skin moistened with a 5 per cent. solution of sodium sulphide, the upper layer of the epidermis is coloured dark; but the perspiration excited by pilocarpin or other agency contains no lead.

§ 790. Fatal Dose—(a.) Sugar of Lead.—It may almost be said that it is impossible to destroy human life with any single dose likely to be taken or administered. In three cases an ounce (28·3 grms.) has been taken without fatal result. Although it must be allowed that repeated moderate doses, extending over some time, are more dangerous to health and life than a single large dose, yet there seems to be in some individuals a great tolerance of lead. Christison has given ·18 grm. in divided doses daily for a long time without any bad effect, save the production of a slight colic. Swieten has also given daily 3·9 grms. (60 grains) in ten days without observing toxic effects. That, in other cases, less than a grain per gallon of some lead compound dissolved in drinking-water, or in some way introduced into the economy, causes serious illness, is most inexplicable.

(b.) The Basic Acetate in solution is more poisonous apparently than the acetate—60 c.c. (1¹⁄₂ drms.) have caused serious symptoms.

(c.) The Carbonate of Lead.—Doses of anything like 28 grms. (an ounce) would probably be very dangerous to an adult; the only case of death on record is that of a child who took some unknown quantity, probably, from the description of the size of the lump, about 10 grms. (2¹⁄₂ drms.).

§ 791. Antidotes and Treatment.—Soluble sulphates (especially magnesic sulphate) have been given largely in both acute and chronic cases; in the acute, it stands to reason that it is well to ensure the presence of plenty of sulphates in the stomach and intestines, in order to form the sparingly soluble lead sulphate, should any residue remain; but to expect this double decomposition to go on in the blood and tissues is not based upon sound observation. The chronic lead-poisoning is best treated by removal from the source of mischief, the administration of large quantities of distilled water, and medicinal doses of potassic iodide.

§ 792. Localisation of Lead.—In a dog, which was killed by chronic lead-poisoning, Heubel found in the bones 0·18 to 0·27 per 1000 of lead; in the kidneys, 0·17 to 0·20; liver, 0·10 to 0·33; spinal cord, 0·06 to 0·11; brain, 0·04 to 0·05; muscles, 0·02 to 0·04; in the intestines traces, 0·01 to 0·02; in the spleen, the blood, and the bile, he also only found traces. Ellenberger and Hofmeister found in the kidneys of the sheep, 0·44 to 0·47; liver, 0·36 to 0·65; pancreas, 0·54; salivary glands, 0·42; bile, 0·11 to 0·40; bones, 0·32; fæces, 0·22; spleen, 0·14; central nervous system, 0·07 to 0·18; blood, 0·05 to 0·12; flesh, 0·05 to 0·08; urine, 0·06 to 0·08; and in the unstriped muscles and the lungs, 0·03 per 1000 of lead.

Without going so far as to say that lead is a natural constituent of the body, it is certain that it may be frequently met with in persons who have been apparently perfectly healthy, and quite free from all symptoms of lead-poisoning. Legrip found in the liver and spleen of a healthy person, 5·4 mgrms. of lead oxide in every kilogram; Oidtmann, in the liver of a man fifty-six years of age, 1 mgrm. of lead oxide per kilogram, and in the spleen 3 mgrms. per kilogram. Hence, the analyst, in searching for poison, must be very careful in his conclusions. Grave and serious errors may also arise from complications; suppose, e.g., that a deceased person previous to death had partaken of game, and inadvertently swallowed a shot—if the analyst had not carefully searched the contents of the stomach for solid bodies, but merely treated them at once with acid solvents, he would naturally get very decided lead reactions, and would possibly conclude, and give evidence to the effect, that a poisonous soluble salt of lead had been administered shortly before death.

§ 793. Detection and Estimation of Lead.—A great number of fluids (such as beer, wines, vinegar, water, &c.), if they contain anything like the amount of one-tenth of a milligramme in 100 c.c., will give a very marked dark colour with SH₂. It is, however, usually safest in the first place to concentrate the liquid, to add an acid, and deposit the lead on platinum, in the way to be shortly described. Nearly all the lead from oils and fatty matter may be dissolved out by shaking up the fat with dilute nitric acid; if necessary, the fat should previously be melted.

If (in the usual course of routine research) a hydrochloric acid solution is obtained from the treatment or destruction of organic substances by that agent, and lead sulphide (mixed possibly with other sulphides) is filtered off, any arsenical sulphide may first be extracted from the filter by ammonia, and any antimonious sulphide by sodic sulphide; then the sulphide may be extracted by warm hydrochloric acid, which will leave undissolved such sulphides as those of copper and mercury. On diluting the liquid, and filtration at a boiling temperature, crystals of lead chloride will be deposited on cooling.

If, however, organic matters are specially searched for lead, hydrochloric acid is not the best solvent, but nitric should always be preferred; and, if there is reason to think that the lead exists in the form of sulphate, then the proper solvent is either the acetate or the tartrate of ammonia; but, in either case, the solution should contain an excess of ammonia. It must, however, be remembered that organic matters retain lead with great tenacity, and that in all cases where it can with any convenience be effected, the substances should be not only carbonised, but burnt to an ash; for Boucher has shown[854] that carbon retains lead, and that the lead in carbon resists to a considerable extent the action of solvents.

In the case of sulphate of lead, which may be always produced in an ash from organic substances by previous treatment with sufficient sulphuric acid, a very excellent method of identification is to convert it into sugar of lead. To do this, it is merely necessary to boil it with carbonate of ammonia, which changes it into carbonate of lead; treatment with acetic acid will now give the acetate; the solution may (if the lead is in very small quantity) be concentrated in a watch-glass, a drop evaporated to dryness on a circle of thin microscopic glass, and the crystals examined by the microscope; the same film next exposed to the fumes of SH₂, which will blacken it; and lastly, the solution (which should be sweet) tasted. A crystalline substance, possessing a sweet taste, and blackening when exposed to SH₂, can, under the circumstances, be no other substance than acetate of lead.

If the analyst does not care for this method, there is room for choice. Lead in solution can be converted into sulphide; in this case it is, however, absolutely necessary that there should be no great excess of acid, since as little as 2·5 per cent. of free hydrochloric acid will prevent all the lead going down. On obtaining the sulphide, the latter, as already described, can be converted into chloride by hydrochloric acid, and the crystalline chloride is extremely characteristic.

From the solution of the chloride the metal may be obtained in a solid state by inserting a piece of zinc in the solution contained in a crucible; the lead will be deposited gradually, and can be then collected, washed, and finally fused into a little globule on charcoal. A lead bead flattens easily when hit with a hammer, and makes a mark on paper. Solutions of the chloride also give a heavy precipitate of lead sulphate, when treated with a solution of sodic sulphate.

When lead is in very minute quantity, an electrolytic method is generally preferable; the lead is precipitated on platinum by using exactly the same apparatus as in Bloxam’s test, described at p. 566; the liquid to be tested being placed in the inner cell, the lead film may now be identified, dissolved in nitric acid, and estimated by a colorimetric process. For the estimation of the minute fractions of a grain by a colour method, it is merely necessary to have a very dilute solution of acetate of lead, to add a known volume of SH₂ water to the liquid to be tested in a Nessler cylinder, noting the colour, and add to another a known quantity of the standard lead solution and the same quantity of SH₂ as was added to the first.

The process has an advantage which is great, viz., that it either detects copper, or proves its absence at the same time; and there are few cases in which the analyst does not look for copper as well as for lead. Lead, if in sufficient quantity, may be most conveniently estimated as oxide, sulphate, or chloride; the chief properties of these substances have been already described.

§ 794. The Detection of Lead in Tartaric Acid, in Lemonade, and Aërated Waters.—To detect lead in tartaric acid a convenient method is to burn it to an ash, digest in a little strong sulphuric acid, and then add either sodic chloride or a drop of HCl; lead, if present, is precipitated as chloride, giving a pearly opalescence. Lemonades often contain minute quantities of iron and copper as well as lead. Neither copper nor iron are precipitated by ammonium sulphide in presence of potassic cyanide. On the other hand, the sulphide of lead is not soluble in the alkaline cyanides. Hence a liquid which, on the addition of potassium cyanide and then ammonium sulphide, becomes dark coloured, or from which a precipitate separates, contains lead.[855]

2. COPPER.

§ 795. Copper, Cu = 63·5; specific gravity, from 8·921 to 8·952; fusing-point, 1091° (1996° F.). Copper in analysis occurs either as a film or coating on such metals as platinum, iron, &c., or in a state of fine division; or, finally, as a bead. In thin films, copper has a yellowish or a yellowish-red colour; it dissolves readily in nitric, slowly in hydrochloric acid. If air be excluded, hydrochloric acid fails to dissolve copper, and the same remark applies to ammonia; but, if there be free access of air, ammonia also acts as a slow solvent. Metallic copper in a fine state of division can be fused at a white heat to a bright bluish-green globule, which, on cooling, is covered with black oxide.

§ 796. Cupric Oxide (CuO = 79·5; specific gravity, 6·5, composition in 100 parts, Cu 79·85, O 20·15) is a brownish-black powder, which remains in the absence of reducing gases unaltered at a red heat. It is nearly insoluble in water, but soluble in ClH, NO₃H, &c.; it is hygroscopic, and, as every one who has made a combustion knows, is readily reduced by ignition with charcoal in the presence of reducing gases.

§ 797. Cupric Sulphide, CuS = 95·5, produced in the wet way, is a brownish powder so insoluble in water that, according to Fresenius, 950,000 parts of water are required to dissolve one part. It is not quite insoluble in ClH, and dissolves readily in nitric acid with separation of sulphur. By ignition in a stream of H it may be converted into the subsulphide of copper. It must always be washed by SH₂ water.

§ 798. Solubility of Copper in Water and Various Fluids.—The solubility of copper in water and saline solutions has been very carefully studied by Carnelley.[856] Distilled water exerts some solvent action, the amount varying, as might be expected, according to the time of exposure, the amount of surface exposed, the quantity of water acting upon the copper, &c. It would appear that, under favourable circumstances, 100 c.c. of distilled water may dissolve ·3 mgrm. of copper (·2 grain per gallon).

With regard to salts, those of ammonium exert a solvent action on copper more decided than that of any others known. With the others, however, the nature of the base exerts little influence, the action of the salt depending chiefly on the nature of its acid radical. Thus, beginning with the least effective, the following is the order of dissolving strength:—Nitrates, sulphates, carbonates, and chlorides. It will then at once be evident that a water, contaminated by sewage, and therefore containing plenty of ammonia and chlorides, might exert a very considerable solvent action on copper.

Almost all the oils and fats, as well as syrups, dissolve small quantities of copper; hence its frequent presence in articles of food cooked or prepared in copper vessels. In the very elaborate and careful experiments of Mr. W. Thompson,[857] the only oils which took up no copper, when digested on copper foil, were English neats’-foot oil, tallow oil, one sample of olive oil, palm-nut oil, common tallow oil, and white oil, which was protected from the air by a thick coating of oxidised oil on its surface.

The formation of copper compounds with the fatty acids takes place so readily that Jeannel[858] has proposed the green colouring of fats by copper as a test for the presence of copper; and Bottger[859] recommends a copper holding brandy to be shaken up with olive oil to free it from copper.

Lehmann has made some useful researches on the amount of copper taken up by fats under different conditions. 100 c.c. of strongly rancid fat dissolved in fourteen days 8·7 mgrms. of copper; but when heated to 160° for one hour, and then allowed to stand, a similar amount was found. Some rancid butter was rubbed into a brass bowl of 90 c.c. capacity, and then allowed to stand for twenty-four hours; the butter became of a blue-green colour. Into this dish, thus partially attacked by fatty acids, 50 c.c. of rancid butter was poured in a melted condition, and allowed to stand for twenty-four hours. The amount taken up was found to be equal to 10 mgrms. of copper for every 100 c.c. of fluid butter.

Hilger found a fatty soup, which had stood twelve hours in a clean copper vessel, to contain 0·163 per cent. copper. According to Tschirch, the easiest fatty salt to form is the oleate, hydrated copper oxide dissolving in oleic acid with great ease, and even copper oxide dissolving to some extent; the palmitate and the stearate are not so readily produced; hence the amount of copper dissolved is greater in the case of olive oil and butter (both rich in oleic acids) than in the case of the firmer animal fats. Acid solutions, such as clarets, acetic acid, vinegars, and so forth, as might be expected, dissolve more or less copper. The amount likely to be dissolved in practice has been investigated by Lehmann. He steeped 600 square metres of copper sheeting or brass sheeting in vessels holding 2 litres of acid claret; the sheets were in some of the experiments wholly immersed, in others partly so. More copper was dissolved by the wine when the copper was partly immersed than when it was wholly immersed; and more copper was dissolved from brass sheeting than from pure copper sheeting. With a sheet of copper, partly immersed, claret may contain as much as 56 mgrms. per litre. Lehmann also investigated the amount of copper, as acetate, which could be dissolved in wine before the taste betrayed its presence: with 50 mgrms. per litre no copper taste; with 100 mgrms. there was a weak after taste; with 150 mgrms. it was scarcely drinkable, and there was a strong after taste; with 200 mgrms. per litre it was quite undrinkable, and the colour was changed to bluish-green. Vinegar, acting under the most favourable circumstances on sheet brass or copper, dissolved, in seven days, 195 mgrms. of copper per litre from the copper sheet, 195 from the brass sheet.

Lehmann discusses the amount of copper which may be taken at a meal under the circumstance that everything eaten or drank has been artificially coppered, but none “coppered” to the extent by which the presence of the metal could be betrayed by the taste; and the following is, he thinks, possible:—

300 c.c. of soup boiled in a copper vessel, 20 mgrms. Cu.

1 litre of wine which has been standing in a copper vessel, 50 „

50 c.c. vinegar which has been kept in a copper vessel, 10 „

50 grms. of fat which has been used for frying in a copper vessel, 5 „

200 grms. of strongly coppered peas, 50 „

500 grms. of strongly coppered bread, 60 „

The total only amounts to 195 mgrms. of copper, which only slightly exceeds a high medicinal dose. The metal is tasted more easily in liquids, such as wine, than in bread; bread may be coppered so that at a meal a person might eat 200 mgrms. of a copper compound without tasting it.

It is pretty well accepted that cooking in clean bright copper vessels will not contaminate any ordinary food sufficiently to be injurious to health.

§ 799. Copper in the Vegetable and Animal Kingdom and in Foods.—Copper is widely distributed in the vegetable kingdom, and is a constant constituent of the chief foods we consume; the following quantities, for example, have been separated from the chief cereals:—

Wheat, 5 ·2 to 10·8 mgrms. per kilo.

Rye, 5 mgrms. „

Oats, 8 ·5 mg„ „

Barley, 11 ·8 mg„ „

Rice, 1 ·6 mg„ „

Bread, 1 ·5 to 4·4 mgrms. „

It has also been found in vermicelli (2-10 mgrms. per kilo.), groats (1·6-3 mgrms. per kilo.), potatoes (1·8 mgrm. per kilo.), beans (2-11 mgrms. per kilo.). In similar small quantities it has also been found in carrots, chicory, spinach, hazel-nuts, blackberries, peaches, pears, figs, plums, tamarinds, black pepper, and many other fruits and spices. The most common food which has a high copper content is cocoa, which contains from 12 mgrms. to 29 mgrms. per kilo., the highest amount of copper being in the outer husk; copper has also been found in many supplies of drinking water, in aërated waters, in brandies, wines, and many drugs.

It has been calculated that the ordinary daily food of an average man contains the following:—

Copper.

900 grms. bread, 0·45 mgrm.

260 grms. meat, 0·25 „

200 grms. fruit and vegetables, 0·25 „

0·95 mgrm.

That is to say, that, neglecting altogether foods artificially contaminated with copper, each of us eats daily about 1 mgrm. of copper (0·015 grain).

In the animal kingdom it is a constant and natural constituent of the blood of the cephalopods, crustacea, and gasteropods, and is nearly always present in the liver and kidneys of domestic animals, as well as in men. Dr. Dupré[860] found ·035 to ·029 grain (1·8 to 2 mgrms.) in human livers, or about 1 part in 500,000. Bergeron and L. L’Hôte’s researches on fourteen bodies, specially examined for copper, fully substantiate those of Dr. Dupré; in twelve the copper was found in quantities of from ·7 to 1·5 mgrm.; in the remaining two the amount of copper was very minute, and was not estimated.[861] Copper is also found normally in the kidneys, and Dupré [862] detected in human kidneys about 1 in 100,000 parts; it is also found in the bile, and in minute traces in the blood.[863]

In the kidneys and livers of the ruminants copper may always be found, a sheep’s liver containing about 1 part in 20,000.[864] Church found copper in the feathers of the wings of the turaco; melopsitt in the feathers of a parroquet (Melopsittacus undulatus).[865] In these cases the copper enters into the composition of the colouring matter to which the name of “turacin” has been given. Turacin contains 7 per cent. of copper, and gives to analysis numbers which agree with the formula of C₈₂H₈₁Cu₂N₉O₃₂.

Copper has been discovered in aërated waters, its presence being due to the use of copper cylinders, the tin lining of which had been rendered defective by corrosion.[866]

Accidents may also occur from the use of copper boilers. Mr. W. Thompson found in one case[867] no less than 3·575 grains in a gallon (51 mgrms. per litre) in water drawn from a kitchen boiler.

At Roubaix, in France, sulphide of copper had been deposited on the roof, as a consequence of the use of copper flues; the sulphide was changed into sulphate by the action of the air, and washed by the rain into the water-tank.[868]

That preserved vegetables are made of a bright and attractive green colour by impregnation with copper, from the deliberate use of copper vessels for this purpose, is a fact long known. Green peas especially have been coloured in this way, and a number of convictions for this offence have taken place in England.

§ 800. The “Coppering” of Vegetables.—The fact that green vegetables, such as peas, beans, cucumbers, and so forth, preserve their green colour, if boiled in copper vessels, has long been known. In this “coppering” the French have been more active than the English traders; the French operate in two different ways. One method is, to dip from 60 to 70 litres of the green vegetables in 100 litres of 0·3 to 0·7 per cent. of copper sulphate, to leave them there for from five to fifteen minutes, then to remove them, wash and sterilise in an autoclave. A second method is to put the vegetables into a copper vessel, the wall of which is connected with the negative pole of an electric current, the positive pole dips in a solution of salt in the same vessel, the current is allowed to pass for three minutes, and the vegetables are afterwards sterilised. Fruits are simply allowed to stand with water in copper vessels, the natural acidity of the juice dissolving sufficient copper.

The amount of copper taken up in this way is appreciable, but yet not so much as might be expected; the prosecutions for selling “coppered” peas in England have been based upon quantities varying from 1 to 3 grains per lb.; the highest published amount of copper found in peas artificially coloured is 0·27 per kilo., or 18·9 grains per lb.

The reason why vegetables preserve their green colour longer when treated with a copper salt has been proved by Tschirch[869] to be owing to the formation of a phyllocyanate of copper.

Phyllocyanic acid is a derivative of chlorophyll, and allied to it in composition; the formula of C₂₄H₂₈N₂O₄ has been ascribed to it. Under the action of acids generally, mineral or organic, chlorophyll splits up into this acid and other compounds. Copper phyllocyanate, (C₂₄H₂₇N₂O₄)₂Cu, contains 8·55 per cent. of copper; it forms black lamellæ, dissolving easily in strong alcohol and chloroform, but insoluble in water; it is a little soluble in ether, insoluble in petroleum ether, and dissolved neither by dilute acetic acid, nor by dilute nor concentrated hydrochloric acid. The compound dissolves in caustic alkali on warming. In alcohol it forms a beautiful non-fluorescent solution. A solution of 1 : 100,000 is still coloured strongly green.

This solution, in a stratum of 25 mm. thick, gives four absorption bands when submitted to spectroscopic observation, and Tschirch has worked out a process of estimation of the amount of copper phyllocyanate based upon the disappearance of these bands on dilution.

Green substances, so carefully treated that they only contain phyllocyanate of copper, would yield but small quantities of copper, and probably they would not be injurious to health; but the coppering is usually more extensive, and copper leguminate and other compounds are formed; for the vegetables, when exhausted by alcohol, give a residue which, successively exhausted by water, by soda-lye, and lastly by hydrochloric acid, parts with copper into the three solvents mentioned.

It might be argued that, from the insoluble character of the phyllocyanate of copper, and especially seeing that it does not dissolve in strong hydrochloric acid, that it would be perfectly innocuous; but Tschirch has proved that, whether the tartrate of copper (dissolving easily in water), or copper oxide (not dissolving at all in water, but soluble in hydrochloric acid), or phyllocyanate of copper (insoluble both in water and in hydrochloric acid) be used, the physiological effect is the same.

Copper may be found in spirits, owing to the use of copper condensers, a remark which applies also to the essential oils, such as oleum cajepute, menthæ, &c.[870] In France, it has been added fraudulently to absinthe, to improve its colour.[871] Green sweetmeats, green toys, green papers, have all been found to contain definite compounds of copper to a dangerous extent.

§ 801. Preparations of Copper used in Medicine and the Arts.

(1) Medicinal Preparations:—

Sulphate of Copper, Cupri Sulphas, CuSO₄5H₂O.—This well-known salt is soluble in water at ordinary temperature, 3 parts of water dissolving 1 of the sulphate; but boiling water dissolves double its weight; 1 part of copper sulphate dissolves in 2¹⁄₂ of glycerin; it reddens litmus, and is slightly efflorescent; its solution responds to all the usual tests for copper and sulphuric acid. A watery solution of the salt to which twice its volume of a solution of chlorine has been added, gives, when treated with ammonia in excess, a clear sapphire-blue solution, leaving nothing undissolved, and thus showing the absence of iron. Besides iron, sulphate of copper has been found to contain zincic sulphate.

Nitrate of Copper, Cu(NO₃)₂3H₂O, is officinal; it is very soluble.

Cuprum Aluminatum.—A preparation, called cuprum aluminatum (Pierre divine), is in use in France and Germany, chiefly as an external wash. It is composed of 16 parts cupric sulphate, 16 potassic nitrate, 16 alum, fused in a crucible, a little camphor being afterwards added.

Regular and irregular medical practitioners, veterinary surgeons, farriers, and grooms, all use sulphate of copper (bluestone) as an application to wounds. Copper as an internal remedy is not in favour either with quacks or vendors of patent medicines. The writer has not yet found any patent pill or liquid containing it.

(2) Copper in the Arts.—Copper is used very extensively in the arts; it enters into the composition of a number of alloys, is one of the chief constituents of the common bronzing powders, is contained in many of the lilac and purple fires of the pyrotechnist, and in a great variety of pigments. The last-mentioned, being of special importance, will be briefly described:—

Pigments:—

Schweinfurt and Scheele’s Green[872] are respectively the aceto-arsenite and the arsenite of copper (see article “Arsenic”).

Brighton Green is a mixture of impure acetate of copper and chalk.

Brunswick Green, originally a crude chloride of copper, is now generally a mixture of carbonate of copper and chalk or alumina.

Mountain Green, or Mineral Green, is the native green carbonate of copper, either with or without a little orpiment.

Neuwieder Green is either the same as mountain green, or Schweinfurt green mixed with gypsum or sulphate of baryta.

Green Verditer is a mixture of oxide and carbonate of copper with chalk.

Verdigris is an acetate of copper, or a mixture of acetates. Its formula is usually represented as (C₂H₃O₂)CuO. It is much used in the arts, and to some extent as an external application in medicine. Its most frequent impurities or adulterations are chalk and sulphate of copper.

§ 802. Dose—Medicinal Dose of Copper.—Since sulphate of copper is practically the only salt administered internally, the dose is generally expressed as so many grains of sulphate. This salt is given in quantities of from ·016 to ·129 grm. (¹⁄₄ to 2 grains) as an astringent or tonic; as an emetic, from ·324 to ·648 grm. (5 to 10 grains).

The sulphate of copper is given to horses and cattle in such large doses as from 30 up to 120 grains (1·9 to 7·7 grms.); to sheep, from 1·3 to 2·6 grms. (20 to 40 grains); rabbits, ·0648 to ·1296 grm. (1 to 2 grains).

§ 803. Effects of Soluble Copper Salts on Animals.—Harnack has made some experiments on animals with an alkaline tartrate of copper, which has no local action, nor does it precipitate albumin. ¹⁄₂ to ³⁄₄ mgrm. of copper oxide in this form, administered subcutaneously, was fatal to frogs, ·05 grm. to rabbits, ·4 grm. to dogs. The direct excitability of the voluntary muscles was gradually extinguished, and death took place from heart paralysis. Vomiting was only noticed when the poison was administered by the stomach.[873] The temperature of animals poisoned by copper, sinks, according to the researches of F. A. Falck, many degrees. These observations are in agreement with the effects of copper salts on man, and with the experiments of Orfila, Blake, C. Ph. Falck, and others.

Roger[874] experimented on the effect of copper leguminate which was administered subcutaneously; he found gradual increasing paralysis of the motor spinal tracts, which finally destroyed life by paralysis of the breathing centre. The heart beat after the breathing had stopped. The irritability and contractility of the muscles of frogs were lost, while sensibility remained. He also found that, if the copper was injected into the intestinal vessels, the dose had to be doubled in order to destroy life; this is, doubtless, because the liver, as it were, strained the copper off and excreted it through the bile. Roger was unable to destroy life by large doses of copper given by the mouth, for then vomiting supervened and the poison in great part was removed.

Bernatzic[875] considers that the poisonous properties of copper are similar to those of zinc and silver. He says: “Silver, copper, and zinc are, in their medicinal application, so much allied that, with regard to their action, they graduate one into the other and show only minor differences; copper, which is a little the more poisonous of the three so far as its remote action is concerned, stands between the other two. If taken, in not too small a quantity, for a long time, the functional activity of the muscular and nervous systems is influenced injuriously, the development of the animal cells is inhibited, the number of the red blood corpuscles decreased, and therefore the oxidising process and metabolism are likewise diminished, leading ultimately to a condition of marked cachexia. . . . From a toxic point of view, the three metals named also stand near each other, and their compounds differ from other metals injurious to the organism in this, that they do not produce notable changes of the tissues or coarse functional disturbances leading to death as other poisonous metals, and therefore are not to be considered poisons in the same sense as lead, mercury, arsenic, antimony, phosphorus are considered poisons; for, on stopping the entry of the poison, any injurious effect is completely recovered from and the functions again become normal.”

Lehmann[876] has also experimented on the effects of copper; his experiments were made on both animals and men. He found that small quantities were more thoroughly absorbed than medium or large doses; the method of separation appeared to be different in different animals—thus, the chief copper-excreting organ in dogs is the liver; in rabbits, the intestine; and in man, the kidneys. Of 3 mgrms. of copper taken by a man in three days, 1 mgrm., or a third, was recovered from the urine. Lehmann experimented on 6 rabbits, 4 cats, and 1 dog. During the first few days the animals were given 10 to 30 mgrms. of copper, in the form of a salt, in their food; then the dose was raised to 50 mgrms. or even to 100 mgrms., and the experiment continued for from two to four months; in one case, six months. The sulphate, acetate, chloride, oleate, butyrate, and lactate were all tried, but no essential difference in action discovered. Apart from slight vomiting, and in a few cases, as shown by post-mortem, a slight catarrh of the stomach, the animals remained well. A few increased in weight. Nervous symptoms, cramps, convulsions, diarrhœa, or the reverse, were not observed. The analysis of the organs showed considerable copper absorption; the liver of the cats gave a mean amount of 12 mgrms. of copper, and in the other organs there was more copper than is found in cases of acute poisoning.

Lehmann has also made experiments upon himself and his pupils on the effect of the sulphate and the acetate when taken for a long time:—

One of the experimenters took for 50 days 10 mgrms. daily Cu as sulphate.

One„of the expe„menters t„ then for 30 „ 20 „ „

Another took for 3 days 5 mgrms. as acetate. sulphate

„ then for 10 days 10 „ „

„ „ 1 day 15 „ „

„ „ 19 days 20 „ „

„ „ 18 days 30 „ „

None of these daily doses had the least effect.

Five farther experiments showed that 75 to 127 mgrms. of copper in peas and beans, divided in two meals, could be taken daily without effect; but if 127 mgrms. were taken at one meal in 200 grms. of peas, then, after a few hours, there might be vomiting; and Lehmann concludes that doses of copper in food of about 100 mgrms. may produce some transient derangement in health, such as sickness, a nasty taste in the mouth, and a general feeling of discomfort, but nothing more; some slight colicky pains and one or two loose motions are also possible, but were not observed in Lehmann’s experiments.

§ 804. Toxic Dose of Copper Salts.—This is a difficult question, because copper salts generally act as an emetic, and therefore very large doses have been taken without any great injury. In fact, it may be laid down that a medium dose taken daily for a considerable time is far more likely to injure health, or to destroy life, than a big dose taken at once. In Tschirch’s[877] careful experiments on animals, he found 10 mgrm. doses of CuO given daily to rabbits, the weight of which varied from 1200 to 1650 grms., caused injury to health, that is, about 3·5 mgrms. per kilo. If man is susceptible in the same proportion, then daily doses of 227·5 mgrms. (or about 3¹⁄₂ grains) would cause serious poisonous symptoms; although double or treble that quantity might in a single dose be swallowed and, if thrown up speedily, no great harm result. 120 grms. of sulphate of copper have been swallowed, and yet the patient recovered after an illness of two weeks.[878] Lewin[879] mentions the case of an adult who recovered after ten days’ illness, although the dose was 15 grms.; there is also on record the case of a child, four and a half years old, who recovered after a dose of 16·5 grms. (a little over half an ounce). On the other hand, 7·7 grms. have been with difficulty recovered from.[880] A woman died in seventy-two hours after taking 27 grms. (7 drms.) of copper sulphate mixed with 11·6 grms. (3 drms.) of iron sulphide; 56·6 grms. (2 ozs.) of copper acetate have caused death in three days; 14·2 grms. (0·5 oz.) in sixty hours.[881]

§ 805. Cases of Acute Poisoning.—Acute poisoning by salts of copper is rare; in the ten years ending 1892, there were registered in England 8 deaths from this cause—3 suicidal (2 males, 1 female) and 5 accidental (4 males, 1 female). The symptoms produced by the sulphate of copper are those of a powerful irritant poison: there is immediate and violent vomiting; the vomited matters are of a greenish colour—a green distinguished from bile by the colour changing to blue on the addition of ammonia. There is pain in the stomach, and in a little time affections of the nervous system, as shown by spasms, cramps, paralysis, and even tetanus. Jaundice is a frequent symptom, if life is prolonged sufficiently to admit of its occurrence.

One of the best examples of acute poisoning by copper sulphate is recorded by Maschka.[882] A youth, sixteen years old, took an unknown large dose of powdered copper sulphate, mixed with water. Half an hour afterwards there was violent vomiting, and he was taken to the hospital. There was thirst, retching, constriction in the throat, a coppery taste in the mouth, and pain in the epigastrium, which was painful on pressure. The vomit was of a blue colour, and small undissolved crystals of copper sulphate were obtained from it. The patient was pale, the edges of the lips and the angles of the mouth were coloured blue, the surface of the tongue had also a blue tint, the temperature was depressed, the extremities cold, nails cyanotic, and the pulse small and quick. Several loose greenish-yellow evacuations were passed; there was no blood. The urine was scanty, but contained neither blood nor albumen. During the night the patient was very restless; the next morning he had violent headache, pain in the epigastrium, burning in the mouth and gullet, but no vomiting. The urine was scanty, contained blood, albumen, and colouring matter from the bile. On the fourth day there was marked jaundice. The mucous membrane was very pale, the temperature low, pulse frequent, and great weakness, cardiac oppression, and restlessness were experienced. There were diarrhœa and tenesmus, the motions being streaked with blood; the urine also contained much blood. The liver was enlarged. The patient died in a state of collapse on the seventh day.

In 1836 a girl, sixteen months old, was given bluestone to play with, and ate an unknown quantity; a quarter of an hour afterwards the child was violently sick, vomiting a bluish-green liquid containing some pieces of sulphate of copper. Death took place in four hours, without convulsions, and without diarrhœa.

§ 806. Subacetate of Copper, Subchloride, and Carbonate, all act very similarly to the sulphate when given in large doses.

§ 807. Post-mortem Appearances.—In Maschka’s case, the chief changes noted were in the liver, kidneys, and stomach. The substance of the liver was friable and fatty; in the gall-bladder there were but a few drops of dark tenacious bile. The kidneys were swollen, the cortical substance coloured yellow, the pyramids compressed and pale brown. In the mucous membrane of the stomach there was an excoriation the size of a shilling, in which the epithelium was changed into a dirty brown mass, easily detached, laying bare the muscular substance beneath, but otherwise normal.

In a case of poisoning by verdigris (subacetate of copper) recorded by Orfila,[883] the stomach was so much inflamed and thickened that towards the pyloric end the opening into the intestine was almost obliterated. The small intestines throughout were inflamed, and perforation had taken place, so that part of the green liquid had escaped into the abdomen. The large intestines were distended in some parts, contracted in others, and there was ulceration of the rectum. In other cases a striking discoloration of the mucous membrane, being changed by the contact of the salt to a dirty bluish-green, has been noticed, and, when present, will afford valuable indications.

§ 808. Chronic Poisoning by Copper.—Symptoms have arisen among workers in copper or its salts, and also from the use of food accidentally contaminated by copper, which lend support to the existence of chronic poisoning. In the symptoms there is a very great resemblance to those produced by lead. There is a green line on the margin of the gums. Dr. Clapton[884] found the line very distinct in a sailor and two working coppersmiths, and the two men were also seen by Dr. Taylor. Cases of chronic poisoning among coppersmiths have also been treated by Dr. Cameron,[885] but this symptom was not noticed. Corrigan speaks of the line round the gums, but describes it as purple-red. Among workers in copper, Lancereaux[886] has seen a black coloration of the mucous membrane of the digestive canal; its chemical characters appear to agree with those of carbon.

Metallic copper itself is not poisonous. A Mr. Charles Reed has published a letter in the Chemical News of Jan. 12, 1894, stating that he was, when a boy, wounded in the shin by a copper percussion-cap, and the cap remained in the tissues; it was removed from the shin after a sojourn thereof some twelve years; about the year 1873 he noticed that whenever a piece of clean iron or steel came in contact with his perspiration it was at once covered with a bright coating of copper, and this continued until the percussion-cap was removed. Presuming the truth of this, it shows conclusively that metallic copper deposited in the tissues is in itself not poisonous, and farther, that one method of elimination is by the skin. The experiments already cited throw doubt as to whether repeated small doses of copper taken for a long time produce in a scientific sense chronic poisoning; those which apparently support the view that there is such a thing as chronic poisoning by copper, have been produced by copper mixed with other metals; and there is the possibility that these cases are really due to lead or arsenic, and not to copper. The great use of late years of solutions of copper sulphate as a dressing to plants, for the purpose of preventing the ravages of various parasites, has provided, so far as animals are concerned, much material for the judgment of this question. Sheep have been fed with vines which have been treated with copper sulphate, oxen and pigs have consumed for a long time grass treated with a 3 per cent. of copper sulphate, without the least health disturbance. Mach[887] has fed cows with green food coppered up to 200 mgrms. of copper sulphate, without observing the slightest bad effect, for long periods of time; and Tschirch[888] summarises the evidence as to chronic poisoning as follows:—“So it appears the contention that there is no chronic poisoning in men or animals is at present uncontradicted; it is farther to be considered proved that the small amounts of copper naturally in food, or carefully introduced into food, are not injurious to the health of those that take such food, because the liver, kidneys, and other organs excrete the copper through the urine and bile, and prevent a pernicious accumulation.” At the same time, Tschirch does not consider the question is definitely settled; the experiments should, he thinks, have been continued not for months, but for years, to obtain a trustworthy judgment.

It may also be remarked that, if we are to rely upon the separation of copper by the kidneys and the liver, those organs are presumed to be in a healthy state, which is not the case with a percentage of the population; to persons whose liver or kidneys are unsound, even the small amounts of copper found in “coppered” peas may act as a poison, and the experiments previously detailed throw no light upon the action of copper under such circumstances.

§ 809. Detection and Estimation of Copper.—Copper may occur either in the routine process of precipitating by SH₂, or it may, as is generally the case, be searched for specially. If copper is looked for in a precipitate produced by SH₂, it is taken for granted that the precipitate has first been treated successively by carbonate of ammonia, sulphide of sodium, and hydrochloric acid; in other words, arsenic, antimony, and lead have been removed. The moist precipitate is now treated with warm nitric acid, which dissolves out copper sulphide with separation of sulphur; if there is sufficient copper, the fluid shows a blue colour, which of itself is an indication of copper being present. The further tests are—(1) Ammonia gives a deeper blue; (2) ferrocyanide of potash a brown-red colour or precipitate; (3) a few drops mixed with a solution of tartrate of soda, alkalised with sodic hydrate, and boiled with a crystal or two of grape-sugar, gives quickly a red precipitate of oxide of copper; (4) a needle or a clean iron wire, or any simple galvanic combination, immersed in, or acting on, the liquid, soon becomes coated with the very characteristic reddish metallic film. Various other tests might be mentioned, but the above are ample.

Special Examinations for Copper.

(1) In Water and Liquids generally.—The liquid may be concentrated, and the copper separated by electrolysis. A simple method is to place the liquid in a large platinum dish, and insert a piece of zinc, adding a sufficient quantity of ClH to dissolve the zinc entirely; the copper is found as an adherent film on the inner surface of the dish. It is neater, however, and more accurate, to connect the platinum dish with the negative plate of a battery, suspending in the liquid the positive electrode. The modifications of this method are numerous; some chemists use (especially for small quantities of copper) two small platinum electrodes, either of foil or of wire, and on obtaining the film, weigh the electrode, then dissolve the copper off by nitric acid, and re-weigh. Such solid substances as peas are conveniently mashed up into a paste with water and ClH; an aliquot part is carefully weighed and put in a platinum dish, connected, as before described, with a battery; at the end of from twelve to twenty-four hours all the copper is deposited, and the dish with its film dried and weighed. The weight of the clean dish, minus the coppered dish, of course equals the copper. Fat and oils are best thoroughly washed with hot acid water, which will, if properly performed, extract all the copper. By the use of separating funnels and wet filters, the fat or oil can be separated from the watery liquid.

A galvanic test has been proposed, which is certainly very delicate, ¹⁄₁₀₀ of a mgrm. in solution being recognised with facility. A zinc platinum couple is made with two wires; on leaving this in an acid liquid containing a mere trace of copper, after several hours the platinum will be found discoloured. If the discoloration is from copper, on exposing the wire to hydrobromic acid fumes (easily produced from the action of potassic bromide and sulphuric acid) and bromine, the wire will become of a violet colour. This colour is easily recognised by rubbing the wire on a piece of porcelain.[889]

(2) Animal Matters, such as the liver, brain, spinal cord, &c., are best entirely burnt to an ash, and the copper looked for in the latter.[890] The same remark applies to bread and substances consisting almost entirely of starchy matters. Any injurious quantity of copper can, however, be extracted with hydrochloric acid and water; and, although this method of extraction is not quite so accurate, it is quicker.

§ 810. Volumetric Processes for the Estimation of Copper.—A number of volumetric processes have been devised for the estimation of copper, but for the purposes of this work it is unnecessary to detail them. When copper is in too small a quantity to be weighed, it may then be estimated by a colorimetric process.

One of the best of these is based upon the brown colour which ferrocyanide of potash produces in very dilute solutions of copper. A standard copper solution is obtained by dissolving sulphate of copper in a litre of water, so that each c.c. contains 0·1 mgrm. Cu, and a solution of ferrocyanide of potash in water is prepared, strength 4 per cent. It is also convenient to have a solution of nitrate of ammonia, which is found to render the reaction much more delicate.

The further details are on the well-known lines of colorimetric estimations.

3. BISMUTH.

§ 811. Bismuth, Bi = 210; sp. gr., 9·799; fusing-point, 264° (507·2° F.).—Bismuth, as obtained in the course of analysis, is either a black metallic powder or an extremely brittle bead of a reddish-white colour. The compounds which it will be necessary to briefly notice are the peroxide and tersulphide.

§ 812. The peroxide of bismuth, Bi₂O₃ = 468; sp. gr., 8·211; Bi, 89·64 per cent., O, 10·36 per cent., as prepared by igniting the carbonate or nitrate, is a pale lemon coloured powder, which can be fused without loss of weight, but is reduced on charcoal, or in a stream of carbon dioxide, to the metallic state. It is also reduced by fusion with potassic cyanide or by ignition with ammonium chloride.

§ 813. The Sulphide of Bismuth, Bi₂S₃ = 516; Bi, 81·25 per cent., S, 18·75 per cent., occurs, in the course of analysis, as a brownish-black or quite black precipitate, insoluble in water, dilute acids, alkalies, alkaline sulphides, sulphate of soda, and cyanide of potassium, but dissolving in moderately concentrated nitric acid with separation of sulphur. It continually increases in weight when dried in the ordinary way, and is completely reduced when fused with cyanide of potassium.

§ 814. Preparations of Bismuth used in Medicine and the Arts.

(1) Pharmaceutical Preparations:—

Bismuthi Subnitras, BiONO₃.H₂O.—A heavy white powder, insoluble in water, and responding to the usual tests for bismuth and nitric acid. The formula should yield 77 per cent. of bismuth oxide. Commercial preparations, however, vary from 79 to 82 per cent.

Bismuth Lozenges (Trochisci bismuthi) are composed of subnitrate of bismuth, magnesia carbonate, precipitated lime carbonate, sugar, and gum, mixed with rose water. Each lozenge should contain 0·13 grm. (2 grains) of subnitrate of bismuth.

Solution of Citrate of Bismuth and Ammonia (Liquor Bismuthi et Ammoniæ citratis), a colourless neutral or slightly alkaline fluid, sp. gr. 1·07, responding to the tests for bismuth and ammonia. As an impurity lead may be present, citric acid being so frequently contaminated with lead. Carbonate of bismuth (Bismuthi carbonas), (Bi₂O₂CO₃)₂H₂O is a fine white powder answering to the tests for carbon dioxide and bismuth; it should yield 89·1 per cent. of bismuth oxide.

A Nitrate of Bismuth, Bi(NO₃)₃, an oleate of bismuth, an oxide of bismuth, a subgallate of bismuth (dermatol), and a subiodide of bismuth are also used in medicine.

(2) Bismuth in the Arts.[891]

The chief use of bismuth is in alloys and solders. The Chromate is employed in calico-printing, and the subnitrate as a paint under the name of pearl-white.

The salts of bismuth also occur in washes for the hair, and pearl-white is used as a cosmetic, but only to a small extent.

§ 815. Medicinal Doses of Bismuth.—The subnitrate and carbonate are prescribed in doses from ·0648 to 1·296 grm. (1 to 20 grains); the valerianate, from ·1296 to ·648 grm. (2 to 10 grains); and the solution, from 1·7 c.c. to 5·2 c.c. (¹⁄₂ drachm to 1¹⁄₂ drachm).

§ 816. Toxic Effects of Bismuth.—From the researches of Meyer and Steinfeld[892] on animals, it appears that if birds or mammals are poisoned with bismuth salts introduced subcutaneously, or by direct injection, into the veins, death follows in from twenty-four to forty-eight hours, the fatal issue being preceded by convulsions; after death, the colon is intensely blackened, and it may be ulcerated, while the small intestines and the stomach are healthy. If, however, sulphur preparations are given by the mouth, there is then blackening of the stomach, and there may also be ulcers. Meyer is of the opinion that SH₂ precipitates bismuth in the parenchyma, and the particles occluding the capillaries thus cause small local necroses; that which escapes precipitation is mainly excreted by the kidneys. Poisonous symptoms in man have been known to occur from the treatment of wounds with bismuth preparations;[893] the symptoms have been somewhat similar to mercurial poisoning; there have been noticed stomatitis with salivation, loosening of the teeth, a black colour of the mucous membrane of the mouth and ulceration, also catarrh of the intestines, and the inflammatory condition of the kidneys usual when that organ has to excrete metallic substances not natural to the body, the “metallniere,” or metal kidney, of the German writers. One case is recorded of death in nine days of an adult after taking 7·7 grms. (2 drms.) of bismuth subnitrate. The recorded symptoms were a metallic taste in the mouth, pain in the throat, vomiting, purging, coldness of the surface, and spasms of the arms and legs. A post-mortem examination showed inflammatory changes in the gullet, windpipe, and throughout the intestinal canal. Recovery has, however, taken place from a single dose three times the amount mentioned. It is possible that the fatal case was due to impure bismuth.

§ 817. Extraction and Detection of Bismuth in Animal Matters.—Bismuth appears to be excreted principally by the bowels as sulphide of bismuth; but it has also been detected in the urine, spleen, and liver; and Lubinsky has found it in the saliva and in the epithelium of the mouth of persons taking one of its preparations. Without denying the possibility of its existing in a soluble state in the saliva, its presence in the mouth may, under such circumstances, be ascribed to the lodgment of particles of subnitrate or subcarbonate of bismuth in the interstices of the teeth, &c. It will then be evident that, if a person is supposed to have been poisoned by a large dose of bismuth, and the analyst fail to find it in the stomach, the contents of the bowels should be next examined.

The extraction of bismuth must be undertaken by nitric acid, and boiling for at least two hours may be necessary to dissolve it out from the tissues. Such organs as the liver and spleen are boiled in a finely divided state with a litre of dilute nitric acid (strength, 5 per cent.), for the time mentioned, filtered, and the filtrate evaporated to dryness; the remainder is then carbonised by strong nitric acid; and, finally, the charcoal is boiled with equal parts of nitric acid and water, and the whole evaporated to dryness. By this method every trace of bismuth is extracted. The dry residue may now be brought into solution, and tested for bismuth. The best solvent for the nitrate of bismuth is dilute nitric acid 50 per cent.; the dry residue is therefore dissolved in 100 or 200 c.c. of the acid, and fractional parts taken for examination:—

(1) The solution, poured into a large volume of warm distilled water, gives a crystalline precipitate of subnitrate of bismuth. The only metal giving a similar reaction is antimony, and this is excluded by the method employed.

(2) The filtered fluid gives on addition of sodic chloride a precipitate of oxychloride. This, again, is distinguished from oxychloride of antimony by its insolubility in tartaric acid.

(3) Any bismuth precipitate, fused with soda on charcoal, gives a brittle bead of bismuth; the coal is coated whilst warm a dark orange-yellow, on cooling citron-yellow.

(4) The bead may be identified by powdering it, placing it in a short subliming tube, and passing over it dry chlorine. The powder first turns black, then melts to an amber-yellow fluid, and finally, by prolonged heating, sublimes as terchloride of bismuth.

(5) A very delicate test proposed by Abel and Field, in 1862,[894] specially for the detection of bismuth in copper (but by no means confined to mineral analysis), utilises the fact that, if iodide of lead be precipitated from a fluid containing the least trace of bismuth, instead of the yellow iodide the scales assume a dark orange to a crimson tint. A solution of nitrate of lead is used; to the nitric acid solution ammonia and carbonate of ammonia added; the precipitate washed, and dissolved in acetic acid; and, finally, excess of iodide of potassium added. It is said that thus so small a quantity as ·00025 grm. may be detected in copper with the greatest ease, the iodide of lead becoming dark orange; ·001 grain imparts a reddish-brown tinge, and ·01 grain a crimson.

(6) A solution of a bismuth salt, which must contain no free HCl, when treated with 10 parts of water, 2 of potassium iodide, and 1 part of cinchonine, gives a red orange precipitate of cinchonine iod.-bismuth.[895]

(7) Van Kobell’s test, as modified by Hutchings,[896] and proposed more especially for the detection of bismuth in minerals, is capable of being applied to any solid compound suspected of containing the metal:—A mixture of precipitated and purified cuprous iodide, with an equal volume of flowers of sulphur, is prepared, and 2 parts of this mixture are made into a paste with 1 part of the substance, and heated on a slip of charcoal on an aluminium support by the blowpipe flame. If bismuth be present, the red bismuth iodide will sublime, and on clean aluminium is easily distinguishable.

There are many other tests, but the above are sufficient.

§ 818. Estimation of Bismuth.—The estimation of bismuth, when in any quantity easily weighed, is, perhaps, best accomplished by fusing the sulphide, oxide, or other compound of bismuth, in a porcelain crucible with cyanide of potassium; the bismuth is reduced to the metallic state, the cyanide can be dissolved out, and the metallic powder washed (first with water, lastly with spirit), dried, and weighed.

Mr. Pattison Muir has shown[897] that bismuth may be separated from iron, aluminium, chromium, and manganese, by adding ammonia to the acid solutions of these metals.

This observation admits of many applications, and may be usefully taken advantage of in the separation of bismuth from the nitric acid solution of such animal matters as liver, &c. The acid liquid is partially neutralised by ammonia, and, on diluting with warm water containing a little sodium or ammonium chloride, the whole of the bismuth is precipitated as oxychloride, which may be collected, and fused with cyanide of potassium, as above.

If the bismuth precipitate is in small quantity, or if a number of estimations of bismuth are to be made, it is most convenient to use a volumetric process. In the case first mentioned, the oxychloride could be dissolved in nitric acid, sodium acetate added in excess, and sufficient acetic acid to dissolve any precipitate which has been produced, and then titrated by the following method, which we also owe to Mr. Pattison Muir:—

Estimation of Bismuth by Potassium Dichromate.[898]—A solution of recrystallised potassium dichromate (strength, 1 per cent.) is prepared. A known weight of pure bismuthous oxide (Bi₂O₃) is dissolved in excess of nitric acid, and a solution of sodium acetate is added to this liquid until a copious white precipitate is thrown down; acetic acid is then added in quantity sufficient to dissolve the precipitate completely, and to insure that, when the liquid is made up with water to a fixed volume, no precipitate shall be formed. A certain volume of this liquid is withdrawn by means of a pipette, placed in a beaker, and heated to boiling; the potassium dichromate is then gradually run in from a burette, the liquid being boiled between each addition of the solution, until a drop of the supernatant liquid gives a faint reddish-brown coloration when spotted with silver nitrate on a white slab.

Another very generally applicable volumetric method for bismuth has been proposed by Mr. Muir.[899] This depends on the fact (observed by Sonchay and Leussen),[900] that normal bismuth oxalate splits up on boiling into a basic oxalate of the composition Bi₂O₃2C₂O₃ + OH₂, but slightly soluble in nitric acid. The process is performed by precipitating the bismuth by excess of oxalic acid, dissolving the precipitate (first purified from free oxalic acid) in dilute hydrochloric acid, and lastly, titrating by permanganate. The absence of free hydrochloric acid before precipitating must be insured.

4. SILVER.

§ 819. Silver = 108; specific gravity, 10·5; fusing-point, 1023° (1873° F.).—Silver, as separated in analysis, is either a very white, glittering, metallic bead, or a dull grey powder. It does not lose weight on ignition, and is soluble in dilute nitric acid.

§ 820. Chloride of Silver, AgCl = 143·5; specific gravity, 5·552; Ag, 75·27 per cent., Cl, 24·73 per cent., is a dense, white, curdy precipitate, when produced in the wet way. It is very insoluble in water, dilute nitric acid, and dilute sulphuric acid; in many warm solutions (especially aqueous solutions of the chlorides generally), the alkaline and alkaline-earthy nitrates, and tartaric acid solutions, the silver is dissolved to an appreciable extent, but deposited again on diluting and cooling. The complete solvents of chloride of silver are—ammonia, cyanide of potassium, and hyposulphite of soda. Chloride of silver cannot be fused at a high heat without some slight loss by volatilisation; on coal in the R.F., it fuses very easily to a globule. It can with soda be reduced to metal, and can also readily be reduced by ignition in a current of hydrogen, carbon oxide, or carburetted hydrogen gas.

§ 821. Sulphide of Silver, Ag₂S = 248; specific gravity, 7·2; Ag, 87·1 per cent., S, 12·9 per cent., when prepared in the wet way, is a black precipitate, insoluble in water, dilute acids, and alkaline sulphides. If ignited in hydrogen it may be reduced to the metallic state; it is soluble in nitric acid, with separation of sulphur.

§ 822. Preparations of Silver used in Medicine and the Arts.

(1) Medicinal Preparations:—

Nitrate of Silver, AgNO₃; Ag, 63·51 per cent., N₂O₅, 36·49 per cent. This salt is either sold crystallised in colourless rhombic prisms, or in the form of small white pencils or sticks. It gives the reactions for silver and nitric acid, and stains the skin black. 100 parts, dissolved in distilled water, should give, with hydrochloric acid, a precipitate which, when washed and dried, weighs 83·4 parts. The silver is, however, far more quickly estimated by the blowpipe than in the wet way. One grm. fused in a cavity on charcoal should give a little globule of metallic silver, weighing about ·6351 grm. The chief adulterations of this substance are copper, lead, and nitrate of potash. If all the silver is precipitated by hydrochloric acid, carefully filtered off, and the filtrate evaporated to dryness, any residue will denote adulteration or impurity.

Argenti Oxidum, Oxide of Silver, Ag₂O = 232; Ag, 93·19 per cent.—A dark olive-brown powder, soluble in ammonia and nitric acid. By ignition it readily yields metallic silver. The P.B. directs that 29 grains of the oxide should yield 27 of metallic silver.

Nitrate of Silver and Potash (Argentum nitricum cum kali nitrico), AgNO₃ + KNO₃.—This preparation is in most of the pharmacopœias, Austrian, German, Danish, Swedish, Russian, Swiss, and the British; it is directed by the B.P. to be composed of 1 part of silver nitrate and 1 part of potassic nitrate fused together. A “toughened silver nitrate” is made by fusing together potassic nitrate 5, silver nitrate 95. Mild caustic points are used by oculists by fusing 1 of silver nitrate with 2, 3, 3¹⁄₂, and 4 parts of potassic nitrate.

(2) Silver in the Arts.—The uses of the metal in coinage, articles for domestic purposes, for ornament, &c., are too well known to require enumeration. The only forms in which silver is likely to give rise to accident are the salts used in medicine, photography, in the dyeing of hair, and in the manufacture of marking inks.

Hair-dyes.—About one-half of the hair-dyes in use are made with nitrate of silver. The following are only a few of the recipes:—

Aqua Orientalis.—Grain silver 2 drms., nitric acid 1 oz., steel filings 4 drms., distilled water 1¹⁄₂ oz.—the whole finally made up to 3¹⁄₂ fluid ozs., and filtered.

Argentan Tincture.—Nitrate of silver 1 drachm, rose water 1 fluid oz., sufficient nitrate of copper to impart a greenish tint.

Eau d’Afrique.—Two solutions—one of nitrate of silver, the other of potash, containing ammonium sulphide.

The photographer uses various salts of silver, the chief of which are—the nitrate, iodide, bromide, cyanide, and chloride of silver.

Marking Inks.—Some of the more important recipes for marking ink are as follows:—

Nitrate of silver 1·0 part, hot distilled water 3·6 parts, mucilage, previously rubbed with sap-green, 1·0 part. With this is sold a “pounce,” or preparation consisting of a coloured solution of sodic carbonate. Another preparation is very similar, but with the addition of ammonia and some colouring matter, such as indigo, syrup of buckthorn, or sap-green. A third is made with tartaric acid and nitrate of silver, dissolved in ammonia solution, and coloured.

Redwood’s Ink consists of equal parts of nitrate of silver and potassic bitartrate, dissolved in ammonia, with the addition of archil green and sugar; according to the formula, 100 parts should equal 16·6 of silver nitrate.

Soubeiran’s Ink is composed of cupric nitrate 3, argentic nitrate 8, sodic carbonate 4, and the whole made up to 100 parts, in solution of ammonia. In one of Mr. Reade’s inks, besides silver, an ammoniacal solution of a salt of gold is used.

§ 823. Medicinal Dose of Silver Compounds.—The nitrate and the oxide of silver are given in doses from ·0162 to ·1296 grm. (¹⁄₄ grain to 2 grains). Anything like ·1944 to ·2592 grm. (3 or 4 grains) would be considered a large, if not a dangerous dose; but nothing definite is known as to what would be a poisonous dose.

§ 824. Effects of Nitrate of Silver on Animals.—Nitrate of silver is changed into chloride by the animal fluids, and also forms a compound with albumen. Silver chloride and silver albumenate are both somewhat soluble in solutions containing chlorides of the alkalies, which explains how a metallic salt, so very insoluble in water, can be absorbed by the blood.

The action of soluble salts of silver on animals has been several times investigated. There appears to be some difference between its effects on warm and cold-blooded animals. In frogs there is quickly an exaltation of the functions of the spinal cord, tetanic convulsions appear, similar to those induced by strychnine; later, there is disturbance of the respiration and cessation of voluntary motion.

The first symptoms with dogs and cats are vomiting and diarrhœa; muscular weakness, paralysis, disturbance of the respiration, and weak clonic convulsions follow. Rouget, as well as Curci, considers that the action of silver is directed to the central nervous system; there is first excitement, and then follows paralysis of the centres of respiration and movement. Death occurs through central asphyxia. According to the researches of F. A. Falck, subcutaneous injections of silver nitrate into rabbits cause a fall of temperature of 6·7° to 17·6°, the last being the greatest fall which, in his numerous researches on the effect of poisons on temperature, he has seen.

Chronic poisoning, according to the experiments of Bogoslowsky on animals, produces emaciation, fatty degeneration of the liver, kidneys, and also of the muscles—a statement confirmed by others.

§ 825. Toxic Effects of Silver Nitrate in Man—(1) Acute Poisoning.—This is very rare. Orfila relates an attempt at suicide; but most of the cases have been accidental, and of these, in recent times, about five are recorded, mostly children. The accident is usually due to the application of the solid nitrate to the throat, as an escharotic, the stick breaking or becoming detached, and being immediately swallowed; such an accident is related by Scattergood.[901] A piece of silver nitrate ³⁄₄ inch long, slipped down the throat of a child, aged fifteen months—vomiting immediately occurred, followed by convulsions and diarrhœa; chloride of sodium was administered, but the child died in six hours. In other cases paralysis and an unconscious state has been observed.

(2) Chronic Poisoning.—Salts of silver taken for a long period cause a peculiar and indelible colour of the skin, the body becomes of a greyish-blue to black colour, it begins first around the nails and fingers, then patches of a similar hue appear in different parts of the body, and gradually coalesce, being most marked in those parts exposed to the light. The colour is not confined to the outer skin, but is also seen in the mucous membranes. There is also a slight inflammation of the gums, and a violet line around their edge. Ginpon observed this line after two months’ treatment of a patient by silver nitrate; the whole quantity taken being 3·9 grms. (about 60 grains). The peculiar colour of the skin is only seen after large dose; after 8 grms. taken in divided doses Chaillon could not observe any change, but after 15 grms. had been taken it was evident. So also Riemer has recorded a case, in which, after a year’s use of silver nitrate (total quantity 17·4 grms.) a greyish-black colour of the face was produced, and, when nearly double the quantity had been taken, the colour had invaded the whole body.

§ 826. Post-mortem Appearances.—In the acute case recorded by Scattergood, the mucous membranes of the gullet, of the great curvature of the stomach, and parts of the duodenum and jejunum were eroded, and particles of curd-like silver chloride adhered to the mucous membrane.

In the case recorded by Riemer of the long-continued use of silver nitrate, the serous and mucous membranes were coloured dark; the choroid plexus was of a blue-black; the endocardium, the valves of the heart, and the aorta pale to dark grey, as well as the rest of the vessels; the colouring was confined to the intima. The liver and kidney also showed similar pigmentation. The pigment (probably metallic silver) was in the form of very fine grains, and, as regards the skin, was situate under the rete Malpighia in the upper layer of the corium, and also in the deeper connective tissue and in the sweat glands. Liouville has also found the kidneys of a woman similarly pigmented, who took silver nitrate daily for 270 days, in all about 7 grms., five years before her death.

§ 827. Detection and Estimation of Silver.—The examination of the solid salts of silver usually met with (viz., the nitrate, bromide, iodide, cyanide, and chloride) is most speedy by the dry method on charcoal; in this way in less than 120 seconds any practical chemist could identify each compound. The nitrate, bromide, iodide, and cyanide, all, if ignited on charcoal, yield buttons of metallic silver—deflagration, bromine vapours, iodine vapours, and cyanogen vapours being the respective phenomena observed. Chloride of silver fuses to a pearl-grey, brown, or black globule on charcoal, according to its purity; but is only in the R.F. gradually reduced to metal. With soda, or fused in hydrogen or coal gas, the reduction is rapid enough.

Nitrate of Silver in solution might be identified by a very large number of tests, since it forms so many insoluble salts. In practice one is, however, satisfied with three tests, viz.: (1) A curdy precipitate of chloride, on the addition of hydrochloric acid or alkaline chlorides, soluble only in ammonia, cyanide of potassium, or hyposulphite of soda; (2) a yellow precipitate, but little soluble in ammonia, on the addition of iodide of potassium; and (3) a blood-red precipitate on the addition of chromate of potash.

The separation of silver from the contents of the stomach is best ensured by treating it with cyanide of potassium; for, unless a very large quantity of silver nitrate has been taken, it is tolerably certain that the whole of it has passed into chloride, and will, therefore, not be attacked easily by acids. The contents of the stomach, then, or the tissues themselves, are placed in a flask and warmed for some time with cyanide of potassium, first, if necessary, adding ammonia. The fluid is separated from the solid matters by subsidence (for an alkaline fluid of this kind will scarcely filter), and then decomposed by hydrochloric acid in excess. The flask containing this fluid is put on one side in a warm place, and the clear fluid decanted from the insoluble chloride. The latter is now collected on a filter, well washed with hot water, and then dried and reduced on charcoal; or it may be put in a little porcelain crucible with a rod of zinc and a few drops of hydrochloric acid. The silver is soon deposited, and must be washed with water, then with sulphuric acid. By the aid of a wash-bottle the particles of silver are now collected on a small filter, again washed, and on the moist mass a crystal of nitrate of potash and a little carbonate of soda laid. The whole is then dried, and all the filter cut away, save the small portion containing the silver. This small portion is now heated on charcoal until a little button of pure silver is obtained, which may first be weighed, then dissolved in nitric acid, and tested by the methods detailed.

In a similar way hair, suspected of being dyed with silver, can be treated with chlorine gas, and the chloride dissolved in potassic cyanide.

Spots on linen, and, generally, very small quantities of silver, may be detected by a simple galvanic process:—The substance is treated with solution of cyanide of potassium, and submitted to a weak galvanic current, using for the negative plate a slip of copper, for the positive, platinum; the silver is deposited on the former.

5. MERCURY.

§ 828. Mercury, Hg = 200; specific gravity, 13·596; boiling-point, 350° (662° F.); it becomes solid at -39·4 (-39 F.). This well known and familiar fluid metal evaporates and sublimes to a minute extent at all temperatures above 5°.

When precipitated or deposited in a finely divided state, the metal can be united into a single globule only if it is fairly pure; very slight fatty impurities especially will prevent the union. It is insoluble in hydrochloric acid, soluble to a slight extent in dilute cold sulphuric acid, and completely soluble in concentrated sulphuric and in nitric acids. It combines directly with chlorine, bromine, and iodine, which, in presence of free alkali, readily dissolve it. It is unalterable at 100°, and, when exposed to a high temperature, sublimes unchanged.

Mercurous Chloride (Calomel, HgCl = 235·5; specific gravity, 7·178; subliming temperature, 111·6°; Hg, 84·94 per cent., Cl, 15·06 per cent.), when prepared in the wet way is a heavy white powder, absolutely insoluble in cold, but decomposed by boiling water. It may be converted into the mercuric chloride by chlorine water and aqua regia. Chloride of ammonium, potassium, and sodium, all decompose calomel into metallic mercury and mercuric chloride. It is easily reduced to metal in a tube with soda, potash, or burnt magnesia.

§ 829. Sulphide of Mercury (HgS, Hg, 86·21 per cent., S, 13·79 per cent.) is a black powder, dissolving in nitromuriatic acid, but very insoluble in other acids or in water. It is also insoluble in alkaline sulphides, with the exception of potassic sulphide.

§ 830. Medicinal Preparations of Mercury.—Mercury in the liquid state has been occasionally administered in constipation; its internal use is now (or ought to be) obsolete. Gmelin has found samples contaminated with metallic bismuth—a metal which only slightly diminishes the fluidity of mercury; the impurity may be detected by shaking the mercury in air, and thus oxidising the bismuth. Mercury may also contain various mechanical impurities, which are detected by forcing the metal by means of a vacuum pump through any dense filtering substance. Tin and zinc may be dissolved out by hydrochloric acid, and all fixed impurities (such as lead and bismuth) are at once discovered on subliming the metal.

Mercury and Chalk (Hydrargyrum cum creta).—Mercury, 33·33 per cent.; chalk, 66·67.

Blue Pill (Pilula hydrargyri).—Mercury in a finely divided state, mixed with confection of roses and liquorice root; the mercury should be in the proportion of 33·33 per cent.[902]

Mercury Plaster (Emplastrum hydrargyri).—Made with mercury, olive oil, sulphur, and lead plaster; it should contain Hg, 33 per cent.; sulphur, 18 per cent.

Ammoniac and Mercury Plaster (Emplastrum ammoniaci cum hydrargyro).—Gum, ammonia, mercury, olive oil, and sulphur; it should contain 20 per cent. of Hg, and ·1 per cent. of sulphur.

Mercurial Ointment (Unguentum hydrargyri).—Mercury mixed with lard and suet, the strength should be nearly 50 per cent. mercury; commercial samples often contain as little as 38 per cent.