LEAD
Metallic lead is not poisonous; but it appears probable that when it is acted upon by the acids of the intestinal secretions, it may become so changed as to produce unpleasant symptoms. Any salt of lead is poisonous when in a condition to be absorbed into the system.
Sugar of lead and white lead are alone important, and will therefore be briefly considered.
Sugar of Lead
Acetate of Lead. Subacetate. Goulard‘s Extract
General Character.—The acetate of lead, better known as sugar of lead, is not unlike loaf-sugar in its general appearance. It is usually met with in the form of solid crystalline masses of a white or brownish-white colour. To the taste it is sweet, a metallic astringent taste being left in the mouth. Acetate of lead is soluble in water and in alcohol. The subacetate is a more active poison than the neutral acetate. Sugar of lead is popularly considered as an active poison, but this does not appear to be the case. Sir R. Christison gave eighteen grains daily in divided doses for eight or ten days with no other unpleasant symptoms than slight colicky pains in the abdomen. Lead is probably eliminated from the system by the urine, and also by the milk; but there is reason to believe that when once deposited in the body, some considerable time is required for its complete elimination. Dr. Wilson is of opinion that in chronic lead poisoning the lead is more largely deposited in the spleen than in any other organ of the body. This organ should therefore always be carefully examined in suspected cases of poisoning by this metal.
Goulard‘s Extract is a solution of the subacetate of lead. It may be of a reddish colour, from the employment of common vinegar in the place of pure acetic acid in the manufacture.
Goulard‘s Lotion is the extract diluted with water.
White Lead
White lead, carbonate of lead, ceruse, or kremser white, is used as a pigment. It is generally in the form of white, heavy chalky masses, insoluble in water, and, when taken in large doses, poisonous. It is this substance which, in the majority of cases, causes chronic lead poisoning, or painter‘s colic.
The chloride and nitrate, the oxides, litharge and red lead, are all poisonous; but the sulphate, due probably to its insolubility, appears to be inert.
Lead poisoning may result from—
1. Constant contact with lead and its salts in manufactories.
2. Its use in the arts and as a pigment. The injurious effects of this substance are strikingly seen among painters, the makers of glazed cards, and the workmen engaged in preparing Brussels lace—this material being whitened by beating white lead into it. All thus employed are liable to suffer more or less from chronic poisoning.
3. Its application to the surface of the body in the form of ointment, plasters, cosmetics, and hair-dyes.
4. Drinking water impregnated with lead, from being stored in leaden cisterns or conveyed in leaden pipes.
“The action of water upon lead is much modified by the presence of saline substances. It is increased by chlorides and nitrates, and diminished by carbonates, sulphates, and phosphates, and especially by carbonate of lime, which, held in solution by excess of carbonic acid, is a frequent ingredient of spring and river water. But water highly charged with carbonic acid may become dangerously impregnated with lead, in the absence of any protecting salt, in consequence of its solvent power over carbonate of lead. In general, water which is not discoloured by sulphuretted hydrogen may be considered as free from lead; but there are few waters which have passed through leaden pipes, or have been retained in leaden cisterns, in which a minute analysis will not detect a trace of the metal; and were it not for the great convenience of lead, iron pipes and slate cisterns would, from a sanitary point of view, be in all cases preferable.
“Another case of contamination by lead may arise from electric action, as where iron, copper, or tin is in contact with or soldered into lead; and in these cases, owing to the action of alkaline bases as well as of acids upon the lead, danger may occur when it is thrown into an electro-negative as well as into an electro-positive state.
“Cisterns are sometimes corroded and their bottoms are perforated by pieces of mortar having dropped into them, the lime of which has caused the oxidation of the metal and a solution of the oxide.”
5. Lead may also find its way into the system by means of the food. Farinaceous foods, chocolate, and tea may become contaminated if lead wrappers be used; and confectionery from the use of lead chromate as a colouring agent. The use of leaden vessels in the manufacture of cider is attended with danger, and also the keeping of pickles in glazed earthenware jars. The celebrated “Devonshire Colic” was the result of cider-making in leaden vats. Beer may be contaminated with lead if allowed to stand in leaden pipes overnight. Rum has been known to have been dangerously impregnated with lead, leaden worms having been used attached to the stills. Many tobacconists are in the habit of using lead foil to wrap up their tobacco and snuff; this practice has resulted in several cases of chronic lead poisoning. Soda and Seltzer waters may contain lead when kept in syphons with leaden caps or valves.
6. Acute and subacute cases of poisoning occur from the taking of lead in the form of diachylon pills to procure abortion.
Symptoms of Poisoning by Lead
Acute.—A metallic taste in the mouth, accompanied with dryness in the throat and intense thirst, is experienced by the patient soon after the poison is swallowed. In some cases, however, two or more hours may elapse before the effects of the poison begin to show themselves. Vomiting may or may not be present. Twisting colicky pains are felt in the abdomen, relieved in some cases by pressure. The paroxysms of pain may be separated by intervals of ease. The bowels are, as a rule, obstinately confined, and the fæces are of a dark colour, from the formation of the sulphuret of lead. The skin is cold, the pulse quick and weak, and there is considerable prostration of strength. In some cases the patient suffers from cramps of the calves of the legs, and sometimes, in protracted cases, paralysis of one or more of the extremities may supervene. The effect on the nervous system, headache, temporary blindness, is marked by giddiness, and stupor, in some cases delirium even resembling acute mania, terminating in coma, or convulsions and death. Albuminuria may occur.
Chronic.—This form of poisoning generally occurs among painters, manufacturers of white lead, pewterers, and others. The early symptoms are those of ordinary colic, only more severe. The patient generally complains, in the first instance, of feeling unwell, and of general debility. He then suffers from pain of a twisting, grinding nature, felt in the region of the navel, the abdomen being retracted and hard. The bowels are obstinately confined. The appetite becomes capricious, and may be entirely lost. The mouth is parched, the breath fœtid, the countenance sallow, the skin dry, and general emaciation sets in. A nasty sweetish metallic taste in the mouth is present in most cases. Not infrequently the subjects of lead poisoning experience a peculiar form of paralysis of the upper extremities, well known as “dropped hand.” It appears that this condition is the result of paralysis of the extensor muscles of the wrist, the long supinator escaping. In other cases the muscles of the shoulder girdle or pelvic girdle and legs may be affected. Acute general paralysis has occurred in workers with lead, and may prove fatal. Optic neuritis and optic atrophy occur in some cases. Persistent headache may be present in others. The muscles undergo a form of fatty degeneration. The lead appears to act primarily on the muscles, then on the nerves, and lastly on the nerve centres. The absorption of lead causes marked anæmia with degeneration of the red corpuscles, which show marked punctate basophilia. One other symptom of importance has yet to be noticed. The gums, at their margins where they join the teeth, present a well-marked blue line, absent where a tooth has been removed. This is not present in all cases, but it should be looked for. Chronic lead absorption produces cardiovascular changes with arterio-sclerosis, valvular degeneration, cardiac hypertrophy, and chronic renal changes with albuminuria. Closely associated with these conditions are saturnine arthritis and gout. The effects upon the vessels may predispose to cerebral hæmorrhage or lead encephalopathy. Cicconardi suggests as a method of diagnosis in lead poisoning, where the cause of the colic is uncertain, to paint the skin with a 6 per cent. solution of sodium sulphite. If lead be the cause the painted part will become darkened in colour.
N.B.—The symptoms produced by white lead—carbonate of lead—are those of colica pictonum, or painter‘s colic, described under the head of Chronic Lead Poisoning.
Post-mortem Appearances.—In acute poisoning the mucous membrane of the stomach and intestines is inflamed, and is in some cases covered by layers of white or whitish-yellow mucus, more or less impregnated with the salt of lead swallowed. Corrosion of the mucous membrane may occur if the dose be large, and this condition is more frequently present when the neutral salt is taken.
In chronic poisoning there are no constant post-mortem appearances. The muscles of the paralysed extremity are usually found flaccid, of a cream colour, and the subject of fatty degeneration.
Fatal Dose.—Sugar of lead is not an active poison, recovery having taken place after one ounce had been swallowed.
Fatal Period.—Uncertain.
Treatment.—The stomach should be emptied by means of the pump or syphon tube, followed by the free administration of the sulphates of soda and magnesia. The carbonates should not be given, the carbonate of lead being poisonous. Vomiting should be promoted, and a powerful cathartic administered. Albumen and milk should also be given, as these precipitate the oxide. In the chronic form of poisoning, the iodide of potash and aperients, notably the sulphate of magnesia, should be administered. Dixon Mann does not consider that iodide of potash is of any value as an eliminator of lead, as the latter forms a stable compound with the tissues. Sulphur baths are also useful in removing the lead from the system. Lately the galvanic bath has been tried with great success. By way of prophylaxis, it has been recommended that all those engaged in lead manufactories, or who are obliged to handle this metal frequently, should partake largely of lemonade made with sulphuric acid, should not take their meals in the factories, or without well washing the hands.
Chemical Analysis.—When the solid acetate is heated on platinum foil, it melts, then solidifies, becomes dark in colour, and gives off fumes of acetic acid.
The following are the liquid tests for lead in solution:
1. Dilute sulphuric acid gives a white precipitate of the sulphate, which is insoluble in nitric, but soluble in hydrochloric acid, in excess of caustic potash solution, and in ammonium acetate solution.
2. Solution of potassium iodide gives a yellow precipitate, soluble in boiling water and caustic potash solution.
3. Sulphuretted hydrogen, or ammonium sulphide, gives a black precipitate.
4. Potassium bichromate a yellow precipitate.
Detection of Lead in Organic Mixtures
The contents of the stomach or vomited matters must be diluted with water and filtered. The residue left on the filter, washed with distilled water, should be set aside for further examination; the filtrate and washings acidified with nitric acid. A current of sulphuretted hydrogen passed through the solution will then throw down the whole of the lead, should any of that metal be present, in the form of a brownish-black sulphide, which may be collected on a small filter and dried. The sulphide, boiled with dilute nitric acid, is partly converted into insoluble sulphate, and in part dissolved as nitrate. The carefully neutralised solution may be either tested at once or carefully concentrated. In either case, the production of a bright yellow precipitate, with a solution of bichromate of potash, and a similar one with a solution of iodide of potassium, may be taken as conclusive of the presence of lead. The portion of lead deposited as sulphate will be found to be soluble in a solution of pure potash, the resulting liquid giving a brown-black precipitate on the addition of sulphide of ammonium.
The insoluble residue left on the filter should be incinerated in a porcelain crucible, either with or without nitric acid, care being taken not to raise the temperature more than is necessary to produce the desired effect: the carbonised mass boiled with dilute nitric acid evaporated to dryness, extracted with distilled water, and then filtered, the filtrate tested as before mentioned. It is often useful, as a preliminary test for the presence of lead in a soluble form, to dip a piece of bibulous paper into the clear liquid obtained by submitting the contents of the stomach or vomited matters to filtration, and then exposing the paper to the action of a current of sulphuretted hydrogen. If lead be present, blackening of the paper will take place.
To detect the lead in the urine and fæces, Dixon Mann advised the urine to be evaporated to the consistency of gruel, and the fæces to be mixed with distilled water to a similar consistence; the organic matters are then to be destroyed with hydrochloric acid and chlorate of potash with the aid of heat, and the solution filtered. The filtrate is then placed in a cell with a parchment bottom, and this into another cell containing distilled water acidulated with sulphuric acid. Two pieces of platinum foil are now placed in the inner and outer cells, separated by the parchment; that in the inner cell is connected with the cathode, that in the outer with the anode of four Grove cells, and the current closed for several hours. The lead, if present, is deposited on the platinum connected with the cathode.
The magnesium method (Marsden & Abram) is useful. A strip of pure magnesium is placed in the urine, to which has previously been added ammonium oxalate, about 1 gramme to 150 c.c. Lead, if present, is deposited on the magnesium in about half an hour, but it may take some hours. The strip is washed in distilled water and dried—warmed with a crystal of iodine the yellow iodide will form; or the deposit may be dissolved in HNO₃ and tested in the usual way.
Goadby recommends inoculating the urine with bacillus coli, which during its growth produces H₂S; this precipitates any lead as sulphide. After filtering, the filtrate is dissolved in a small quantity of 10 per cent. nitric acid and tested by the usual methods.
Recapitulation of the Leading Facts with
regard to Poisoning by Lead