ARSENIC
Arsenic is found as metallic arsenic, as arsenious acid, in the form of two sulphides—realgar and orpiment, and as a constituent of several ores—iron, copper, &c.
Metallic arsenic is of a steel-grey colour, brittle, and sublimes at a temperature a little below 400° F., without, however, previously fusing. The vapour of the metal has a peculiar garlic-like odour, which is not possessed by any of its compounds.
Arsenious Acid
Arsenious anhydride—white arsenic—the most important of all the compounds of arsenic, is colourless, odourless, and almost devoid of taste. As found in commerce, it occurs under two forms—as a white powder, and as a solid cake, which is at first nearly transparent, but soon becomes opaque, and then resembles white enamel. At a temperature of about 380° F. it sublimes, but is again deposited on cool surfaces in the form of octahedral crystals. It is but slightly soluble in cold water, only about half a grain to a grain being taken up by an ounce of water. Stirred in boiling water, and then allowed to cool, from a grain to a grain and a quarter is dissolved in the same quantity of water; but when it is boiled for an hour, about twelve grains are dissolved in the ounce of water. This solubility is, however, diminished by the presence of any organic matter in the liquid. It is therefore less soluble in infusions of tea or coffee than in pure water. A teaspoonful of powdered arsenic is said to weigh 150 grains, and a pinch 17 grains.
Arsenious acid is used in the arts in the manufacture of certain green colours, in dyeing, and in calico printing. A weak solution is employed in medicine in the treatment of certain diseases of the skin, in ague, and in other diseases.
It has been proposed to use arsenious acid, on account of its caustic properties, as an application for cancerous tumours. The employment of this substance for this purpose is by no means new; but its use has been revived from time to time by the charlatan. In the year 1844, a man was tried at the Chester Winter Sessions (R. v. Port) for the murder of a woman whom he pretended to cure of a cancer by the use of an arsenical plaster. In another case, recorded by M. Flandin, where death occurred, the quack declared that he had not applied more than four or five grains to the woman‘s breast. The powder used for this purpose is generally composed of arsenious acid, realgar, and oxide of iron. The above cases, to which many more might be added, attest to the danger which attends the application of arsenic to the surface of the body; it should, therefore, never be used, especially as a more safe and potent caustic for this purpose is found in the chloride of zinc. Some years ago, in London, several cases of severe arsenical poisoning were due to the presence of arsenic in some cheap violet powder. In one case the navel and scrotum of a baby were fearfully excoriated, due to the use of this powder.
Farmers employ arsenious acid (white arsenic) for destroying vermin: for steeping corn in order to destroy any spores of fungi; and it also forms an ingredient in the wash for sheep. Injurious effects have followed the accidental use of the corn thus treated, and those employed in washing the sheep have suffered more or less severely.
By an Act of Parliament (14 Vict. cap. xiii. sec. 3), it is ordered that if sold in small quantities, it must be mixed with the sixteenth part of its weight of soot, or the thirty-second part of its weight of indigo, ten pounds being the smallest quantity allowed to be sold unmixed.
The presence of this admixture must be remembered, as a medical man may be led into an error when the vomited matters are coloured blue, black, or green, from the mixture of bile with the indigo. Arsenic is not, as a rule, a corrosive poison. One case is, however, on record where it acted as a corrosive, but the purity of the arsenic in that case has been questioned. Its action is that of an irritant, causing inflammation in the stomach and bowels of those who have taken it; and it appears that fatal effects are produced whether the poison be swallowed or introduced into the system in any other way—e.g. by injection into the rectum or vagina, or applied to the surface of the body.
Some observers hold that arsenic cannot be considered in the light of an accumulative poison, others that it is so to a certain extent, and that its elimination is not so rapid as was previously thought. Given in medicinal doses, it is eliminated in from fifteen to twenty days. Hence, in cases which have survived the immediate action of the drug, no arsenic may be found in the body fifteen days after its fatal administration. This is a fact of considerable importance. In the case of Pierre Emile L‘Angelier, for whose murder Madeline Smith was tried, Dr. Penny found 88 grains in the stomach, although the deceased survived eight or ten hours after the probable period of taking the poison, and vomited repeatedly during that time. At the above trial, the question was suddenly raised, that if such a large quantity was found after death in the stomach, it was scarcely possible to infer the administration of a much larger quantity; and thus, that the quantity must have been larger than another party could have secretly administered, or naturally would attempt to administer. Drs. Mackinlay and Wylie, of Paisley, obtained 60 grains, and Sir R. Christison 30 grains more, from the stomach of a man poisoned by arsenic administered in whisky-punch sweetened, the arsenic being kept in suspension by constant stirring.
Symptoms of Arsenical Poisoning
Acute.—The rapidity and virulence of the symptoms are more or less modified by the form (e.g. solution) and the dose taken. From half an hour to an hour is the usual time which elapses before the symptoms of poisoning present themselves. In one case, in which the poison was in solution, the symptoms came on immediately after it was swallowed; in another, after the lapse of ten hours. The patient first complains of a feeling of faintness and depression, followed by intense burning pain in the stomach, increased by the slightest pressure. Nausea and vomiting, the latter increased by the act of swallowing, now occur. The vomited matters may be dark brown, black, or bilious; or they may be greenish from the indigo mixed with the arsenic coming in contact with the yellow colouring matter of the bile. Blood may also be vomited. Purging, accompanied with straining at stool, and cramps in the calves of the legs may occur—the purging, like the vomiting, being incessant, and affording no relief to the sufferer; the stools may contain blood, or resemble those of cholera. The thirst is intense, and there may be a feeling of throat irritation, the pulse feeble and irregular, and the skin cold and clammy. The urine may or may not be suppressed. As a rule, the symptoms in this form of poisoning are continuous; but cases occur in which there are distinct remissions, and even intermissions. Coma, paralysis, or tetanic convulsions may supervene before death closes the scene.
Certain anomalies may occur.—The pain may be absent or but slight. Vomiting and purging do not occur in all cases, nor is thirst, a most common and persistent symptom, always present. In some cases the symptoms resemble those which accompany an attack of cholera. In others, signs of collapse first make their appearance, from which the patient may rally, or he may die outright. These variations in the symptoms do not appear to be due to the form or quantity of the poison taken. It should also be remembered that arsenic may produce symptoms closely resembling those the result of narcotic poisoning.
Chronic.—In whatever way the poison be exhibited in small and repeated doses, there follows a peculiar and characteristic train of symptoms, associated with (a) the general nutrition of the body, (b) the facial appearance, (c) irritative disturbance of the alimentary canal, (d) skin eruptions, and (e) implication of the nervous system.
(a) The nutrition of the body is altered, there is gradual loss of flesh with ragged growth of the finger-nails and falling out of the hair. There may be œdema and jaundice in some cases.
(b) The face presents a peculiar appearance, the eyes are inflamed and watery, the conjunctivæ reddened and congested, there is excessive secretion from the nose resembling coryza.
(c) The disturbance of the digestive organs is revealed by the dryness of the mouth and occasional excoriation of the tongue, which may be reddened or covered with white fur and silvery in appearance; salivation may be present instead of dryness of the mouth; there may also be irritation of the throat; symptoms of gastro-enteritis, e.g. nausea and vomiting, anorexia, diarrhœa, or alternating diarrhœa and constipation.
(d) The skin eruptions are of various kinds, and comprise eczema, herpes, urticaria, erythema, keratosis, marked pigmentation and exfoliation.
(e) The nervous symptoms are those of peripheral neuritis, numbness, formication, hyperæsthesia, and tenderness, especially of the soles of the feet, the latter presenting appearances of erythro-melalgia; there is some amount of paresis, in some cases amounting to absolute paralysis of the limbs affected. The hands may be anæsthetic, while the feet are hyperæsthetic and hyperalgesic, and the perspiration much increased. Mental symptoms are not common, but there may be hebetude, or delusions.
In the Maybrick case, tried at the Liverpool Assizes in 1889, the following symptoms arose from repeated administration of arsenic during a period of probably about fourteen days. On April 27 Mr. Maybrick was seized with vomiting after taking tea. On the next day the vomiting continued, with foulness of the tongue, and he complained of stiffness in the lower limbs. On May 1 he complained of feeling unwell after taking luncheon, and he was sick on the following three days, and complained of a tickling sensation in the throat, with retching. On May 7 he was still suffering from vomiting, diarrhœa had commenced, and the throat was very dry and inflamed. On May 8 the diarrhœa was accompanied by tenesmus. On May 9 the tenesmus was distressing, and he died on May 11.
Dr. Prosper de Pietra Santa describes a disease to which workers in manufactories of paper coloured with Schweinfurt-green are liable, characterised by the appearance of vesicles, pustules, plaques muqueuses, and ulcerations on the exposed parts of the body, fingers, toes, and scrotum. Arsenical poisoning has been mistaken for nettle-rash, scarlet fever, and Addison‘s disease. In cases of slow poisoning the symptoms resemble very much those of gastritis and ulcer of the stomach, and death due to the action of arsenic has been referred to “spontaneous inflammation of the bowels.”
It must be remembered that in some cases of acute arsenical poisoning, when the acute symptoms have passed away, the nervous system exhibits its effects at a later period; in one case paresis came on on the fifth day, in another at the end of a week, and in a case recorded by Seeligmüller four weeks elapsed before the onset of nervous symptoms.
Post-mortem Appearances.—The appearances found after death depend upon the quantity of the dose and the length of time which supervenes between the taking of the poison and death. Inflammation of the stomach is a marked effect of the action of this substance on the system; and this condition is in most cases present whether the poison be swallowed, sprinkled on an ulcerated surface, or rubbed into the skin. The inflammatory redness, which may assume the appearance of crimson velvet, may be found in cases where death has taken place in two hours. It is sometimes found spreading over the entire surface of the stomach; at others, at the cardiac end only. The red colour is increased on exposing the stomach to the air. When the poison has been swallowed, the stomach may be found covered with white patches of arsenic, embedded in dark-coloured thick mucus, mixed with blood. Dr. Paterson thus describes the condition of a stomach he examined: Its lining membrane was generally very red and injected; but in addition there were very numerous stellated patches of vivid red, leading to a darker tint; in the centre of some of them was noticed a minute clot of blood; in others, an exceedingly rough particle of a crystalline substance, which was afterwards found to be arsenious acid. Perforation of the stomach is extremely rare, if it has ever occurred, but ulceration of the same organ has been observed in a person who died from the effects of arsenic in five hours (Christison, on Poisons, p. 340). In opposition to all the statements just made it has been shown that arsenic may prove fatal without leaving any sign of inflammatory action (R. v. M‘Cracken; R. v. Newton).
The mouth, pharynx, and gullet are generally found free from any inflammatory action. The small intestines may or may not be affected: in most cases the duodenum alone shows any signs of irritation. The rectum is that part of the large intestine most prone to inflammation. I have seen marked ulceration of the colon after death from inhalation of arseniuretted hydrogen. The other internal organs—the liver, spleen, and kidneys—do not appear to be appreciably affected by arsenic.
Due probably to the antiseptic properties of arsenic, the stomach and intestines retain for a long period after death the appearances of irritant poisoning. In two cases, this was so well marked as to be visible—in the one case, twelve months, and in the other, nineteen months after interment. In suspected cases portions of the liver should always be preserved and examined for arsenic.
The Period after Death when
Arsenic may be Detected
Arsenic is an indestructible poison, and may be found in the body after many years. In one case it was detected after the lapse of fourteen years. Arsenic has the power, to a certain extent, of arresting putrefactive changes; the stomach may, therefore, be found well preserved, and with the signs of inflammatory action present after the lapse of many months, and after putrefaction has far advanced in other parts of the body. When a person is suspected of having been poisoned with arsenic, and nothing but the skeleton is left for investigation, the arsenic should be looked for specially in the bones of the pelvis and the neighbouring vertebræ (Watt‘s Dictionary of Chemistry, Sup.).
In reference to the preservative action of arsenic upon the tissues of those poisoned by it, the appearances of the bodies of the victims of Flannagan and Higgins, recorded by Whitford (B. M. J., 1884, vol. i. p. 504), are interesting. Arsenical poisoning having been established in one of three victims, the bodies of two others, Mary Higgins, aged ten years, and John Flannagan, aged twenty-four years, were exhumed and examined. The abdominal viscera of Mary Higgins yielded one grain of arsenious acid, and although the body had been interred for about thirteen and a half months, it was well preserved. A remarkable state of preservation obtained in the body of John Flannagan, who had been interred for thirty-seven and a half months; the face and body generally could be easily identified. Three and a half grains of arsenious acid were found in the abdominal viscera. In these cases a peculiar appearance was found in the stomach and intestines, consisting of a golden-yellow pigment or coating of the mucous membrane of the parts. It was thought by some observers to be composed of arsenic sulphide, but Campbell-Brown, and Davies of Liverpool, as a result of their analysis of it, found that it did not contain any appreciable amount of arsenic, but consisted mainly of bile pigment.
In trials for arsenical poisoning, where an exhumation has been made, the question may arise whether the arsenic found in the body has been carried into it from the earth surrounding the coffin.
In reply, the following points must be kept in mind:
1. Arsenic may occur in certain calcareous and ochrey soils.
2. In these soils no arsenical compound soluble in water has been found.
3. The arsenic of these soils is dissolved out by hydrochloric acid, proving their previous insolubility.
4. The arsenic is, therefore, probably in the form of an arsenite or arseniate of iron, lime, &c.
5. Careful experiments have rendered it evident that even “under the most favourable circumstances the dead human body does not acquire an impregnation of arsenic from contact with arsenical earth” (Taylor).
6. It has been suggested that the arsenical compound in the soil may be rendered soluble by the ammonia formed during putrefaction.
This last suggestion is negatived by the following facts:
1. The production of ammonia ceases before the body arrives at that stage of decomposition when it is at all likely to be exposed to the action of the soil of the cemetery.
2. The production of hydrosulphuret of ammonia during decomposition would tend to the production of sulphuret of arsenic forming yellow patches in the substance of the organs, thus rather fixing the arsenic on particular parts than allowing it to percolate through the tissues of the body from external application.
Analysis of the Suspected Earth.—About two pounds of the earth should be boiled for some time in water; supernatant liquid should then be poured off from the insoluble residue, and filtered. The filtered liquid, after concentration, may then be examined by the tests about to be described. If no arsenic be found, the earth may now be boiled with dilute hydrochloric acid, filtered, concentrated, and then tested as before. The first process shows that no compound of arsenic soluble in water is present; the second shows that the arsenic is in a state of combination, and therefore not likely to impregnate the body.
The Detection of Arsenic
General Directions.—In cases of suspected poisoning by arsenic or antimony, the contents of the stomach should be mixed with distilled water acidulated with hydrochloric acid and filtered, and the filtrate placed in a stoppered bottle lettered or numbered “A” or “1.” The liver should be cut into pieces, some of which should be bruised in a mortar with distilled water acidulated as above mentioned, pressed and filtered, and the filtrate placed in a bottle marked “B” or “2.”
The kidneys and portions of the other solid organs may also be treated as above. Each solution so obtained may be then tested by the processes about to be described. By these means the amount of poison in each organ may be estimated.
Before subjecting the organic mixture to Marsh‘s or Reinsch‘s processes, Brande and Taylor strongly recommend a modified course of procedure.
The contents of the stomach, vomited matters, &c., and the solid organs, finely divided, must each be separated and thoroughly dried in a water bath, then mixed with an excess of strong hydrochloric acid in a flask, and slowly distilled by means of a sand bath, the distillate carried into a receiver containing a little pure distilled water, and the process continued nearly to dryness.
If arsenic be present, the distillate contains the arsenic as chloride, and can be at once subjected with great facility to the usual tests for the presence of that metal. This mode of proceeding both facilitates and expedites the ordinary methods of testing, as it separates the arsenic present from the complex organic mixtures with which it is associated, and presents it in a comparatively pure form for identification. The process also admits of the residue left in the retort being examined for lead and the other metallic poisons.
Before the following processes are applied, some of the sediment from the contents of the stomach, or the vomited matters, may be collected and well washed. If this is boiled in distilled water and filtered, the following tests, known as “the liquid tests for arsenic,” may be applied to the filtrate:
1. Ammonia Nitrate of Silver, prepared by adding a weak solution of ammonia to a strong solution of nitrate of silver, gives with arsenic a yellow precipitate of arsenite of silver soluble in nitric, citric, acetic, and tartaric acids, and ammonia.
2. Ammonia-Sulphate of Copper, prepared by adding ammonia to a dilute solution of sulphate of copper, gives with arsenic a green precipitate of arsenite of copper. This precipitate is soluble in the mineral and vegetable acids and ammonia, but is not affected by soda or potash. The precipitate, dried and heated in a reduction tube, yields octahedral crystals of arsenious acid.
3. Sulphuretted Hydrogen.—The suspected liquid should be first slightly acidulated with pure hydrochloric acid before the sulphuretted hydrogen gas is passed into it, when, if arsenic be present, a yellow precipitate is formed, known to be such by the following tests:
(1) Insoluble in water, ether, alcohol, the vegetable acids, and dilute hydrochloric acid, but decomposed by strong nitric and nitro-hydrochloric acids.
(2) Dissolved, if no organic matter present, forming a colourless solution, when potash, soda, or ammonia is added.
(3) The yellow precipitate dried and heated with soda and cyanide of potassium yields a sublimate of metallic arsenic.
N.B.—None of the above tests should be applied in the presence of organic matter. The soluble salts of cadmium and per-salts of tin give yellow-coloured precipitates with sulphuretted hydrogen.
(4) If stannous chloride dissolved in strong hydrochloric acid be added to a solution of arsenic in hydrochloric acid, metallic arsenic is thrown down as a precipitate. This is a fairly delicate test.
The following Table gives the differences between the
Yellow Precipitates formed with Sulphuretted Hydrogen
and Arsenic, Cadmium, and Per-Salts of Tin:
| Arsenic. | Cadmium. | Per-Salts of Tin. | |
|---|---|---|---|
| Colour. | Yellow. | Yellow. | Dirty yellow. |
| Action of ammonia. | Soluble. | Insoluble. | Insoluble. |
| Action of hydrochloric acid. | Insoluble. | Soluble. | |
| With cyanide flux. | Sublimes as metallic arsenic. | Sublimes as brown oxide. | No sublimate. |
Marsh‘s Process.—This method for the detection of arsenic is founded on the fact that the several compounds of arsenic, except the sulphide and metallic arsenic itself, form a gaseous compound with nascent hydrogen, from which it may be readily separated by appropriate treatment. The solution to be tested should, therefore, be prepared as proposed by Brande and Taylor, given on a preceding page.
Precautions.—(1) Absolute purity of reagents. (2) The sulphuric acid should be diluted with five times its weight of water, and allowed to cool. (3) The suspected fluid should be added gradually. (4) Generate the gas regularly. (5) If no stain be at once produced, keep a portion of the exit tube red-hot for at least one hour.
The usual form of the apparatus is that of a U-shaped glass tube, about one inch in diameter and eight inches high, supported in a vertical position on a wooden stand. One end of the tube is fitted with a tap, and terminates in a glass tube drawn to a fine point; the other end is closed with a cork.
The apparatus is used as follows: A piece of pure zinc is dropped into the tube, and shaken into such a position that it occupies the bottom of that limb of the tube which is furnished with the tap. Water is then added, and subsequently sufficient pure sulphuric acid to cause a moderately brisk evolution of hydrogen. The production of hydrogen gas from pure zinc and pure sulphuric acid is sometimes slow, and may be facilitated by adding a few drops of platinic chloride solution to the contents of the flask previous to the addition of the sulphuric acid. The gas being allowed to accumulate for a short time, the tap is then partially turned on, and the gas ignited; if, on depressing a piece of white porcelain momentarily in the flame, no deposit or discoloration occur, the reagents used may be taken as pure. By the use of Thorpe‘s apparatus for Marsh‘s test, in which the hydrogen is obtained by the electrolysis of water, the absence of arsenic in the reagents and apparatus is ensured. The tap is now connected with a tube of thin, hard glass, drawn out to a fine point at the end and having a constriction in the middle. The liquid to be tested being now placed in the apparatus, the gas is again ignited, and a piece of white porcelain momentarily depressed in the flame, when, if arsenic be present, a black, circular, metallic-looking stain will appear, which has the following composition. In the centre is the unoxidised metal, round this is a mixed deposit, and outside this the zone of arsenious acid. While the gas is passing, the exit tube should be heated to redness a little behind the constricted part, when a dark ring will appear if arsenic be present. The black deposit on the porcelain may be either arsenic or antimony, but may be distinguished as follows:
| Arsenic. | Antimony. | |
|---|---|---|
| Nature of the stain. | Metallic brilliancy | Absence of metallic lustre. |
| Effect of heat. | Volatile. | Non-volatile. |
| Heated with a little | Dissolves. | Oxidises to a white |
| nitric acid. | insoluble powder. | |
| Warmed with a strong | Dissolves immediately. | Slowly dissolved. |
| solution of chloride | ||
| of lime. | ||
| Treated with | Detached but not dissolved, | Soluble: on evaporation, |
| bisulphide of | but if heated to drive off | orange-yellow sulphide |
| ammonium. | ammonia yellow sulphide | formed. |
| formed. | ||
| The nitric acid | A brick-red precipitate | No reaction, but if |
| solution evaporated | soluble in ammonia | ammonia and potash |
| to dryness gives | are added, a black | |
| with nitrate of silver. | precipitate is ultimately | |
| formed. |
The portion of the tube on which the dark ring has been deposited is now cut off, broken into fragments, and heated in a small, hard glass tube—when, if arsenic be present, a white sublimate will be obtained of well-defined octahedral crystals. If the sublimate be treated with sulphide of ammonium, it is detached but not perfectly dissolved, and on evaporation of the solution to dryness, a residue of the yellow sulphide of arsenic will remain, which, if heated with strong nitric acid, and evaporated again to dryness, will give a brick-red precipitate with nitrate of silver solution, soluble in ammonia. The process of Marsh may be used quantitatively by passing the issuing gas through a glass tube, dipping into a strong solution of argentic nitrate. A portion of the tube is kept at a red heat, when, if arsenic be present, it is deposited in the metallic form in the cool portion. The glass tube containing the stain is cut with a file and weighed. The stain is then removed by strong nitric acid, the tube dried and weighed: the difference in weight equals the amount of metallic arsenic. The nitrate of silver solution is now treated with pure hydrochloric acid, filtered, and the filtrate neutralised with sodium carbonate, titrated with standard solution of iodine. By dipping the end of the issuing tube into a fresh solution of argentic nitrate, the absence of colour will show that all the arsenic has been obtained.
Instead of the U-shaped tube a Wolff‘s bottle or Erlenmeyer‘s flask may be used, and the exit tube carrying off the gas bent twice upon itself and connected with a glass bulb containing calcium chloride. From this bulb the long, hard glass tube proceeds, pointed at the end to form a gas jet; the gas is lighted at the end, and if a Bunsen flame be applied at a short distance from the end, a deposit of the arsenic, if present, will form on the distal side of the point at which the flame is applied.
Reinsch‘s Process.—First obtain a clear solution by filtration or otherwise, and then proceed as follows: Strongly acidify the liquid with hydrochloric acid, introduce some pieces of copper foil, and heat to near the boiling-point of the liquid. Both the acid and metal must be previously tested to ensure their freedom from arsenic. Any arsenic present will then be deposited on the copper in the metallic state, either in the form of a black lustrous deposit when the arsenic is present in any quantity, or else as a steel-grey coating when a minute quantity only is present. In either case, the copper foil, after remaining for some time in the suspected fluid, is taken out, cut into small pieces, introduced into the bottom of a hard glass tube, and heated to low redness, when the arsenic will sublime as arsenious acid in octahedral crystals, forming a ring in the cooler portion of the tube. The deposit is identified as arsenious acid by the form of the crystals, and by its deportment with the various reagents, as in the treatment of similar sublimates mentioned under Marsh‘s Process. Two precautions have to be taken in applying this test: do not use too large a portion of copper foil at first, and do not remove the copper too quickly from the boiling fluid. A solution containing arsenic acid or an alkaline arsenite, mixed with sulphuric acid, does not produce any deposit on metallic copper even after long boiling, unless the quantity of the arsenic present be considerable; the deposition may, however, be ensured by adding sulphurous acid or a sulphite, whereby the arsenic is reduced to arsenious acid (G. Werther, J. Pr. Chem., lxxxii. 286; Jahresb., 1861, p. 851).
Objections to Reinsch‘s Process.—The chief objection to Reinsch‘s process is the possible impurity of the reagents used—both these reagents, even when supplied as pure, being liable to contain traces of arsenic. As met with in commerce, both hydrochloric acid and metallic copper invariably contain minute quantities of arsenic, the former generally containing the larger quantity of that impurity. Although, by purchasing the purest possible reagents, specially prepared for analysis, it may be possible to ensure their freedom from arsenic, yet in all cases they should be tested before using them. Some of the hydrochloric acid should be diluted with distilled water, and gently heated with the copper foil. If no tarnishing or deposit of any kind occur on the metal after a lapse of several hours, the reagents may be taken as pure and the trial of the suspected substance at once made.
Professor Abel has proposed the following process to ensure the purity of the copper and acid: Boil together equal portions of strong hydrochloric acid and a solution of perchloride of iron. While the mixture is boiling immerse the copper foil, which, if pure, will be merely brightened in colour; if impure, a black deposit on the metal is formed.
Fig. 30.—Photo-micrograph of
sublimate of arsenious acid obtained
by Reinsch‘s process, × 250.
(R. J. M. Buchanan.)
Bloxam‘s Method for the Detection of Arsenic.—The late Professor Bloxam suggested an admirable and delicate process for the detection of small quantities of arsenic. The method is, like that of Marsh, founded on the property possessed by nascent hydrogen of forming a gaseous compound with arsenic; but, instead of the hydrogen being generated by the action of dilute sulphuric acid on zinc, Bloxam generates the gas by an electric current.
The wires from the extremities of a battery terminate in small plates of platinum foil, which are plunged into the liquid to be tested, the apparatus being so arranged that the hydrogen gas evolved from the negative pole is collected. The issuing gas is tested in a similar manner to that obtained in Marsh‘s process.
This method of Bloxam‘s is exceedingly delicate, and possesses one great advantage, that no zinc being used, there is no danger of contamination by the use of impure metal; while, as nothing foreign is introduced during the process of testing, the liquid under examination is left pure for the application of other tests if necessary.
Fig. 31.—Dowzard‘s apparatus for Gutzeit‘s test for
arsenic. A and B indicate glass cells or traps which contain
solutions of lead acetate and copper chloride for the purpose of
fixing H₂S and PH₃ which otherwise would react upon the mercuric
chloride spot on the filter-cap. The cells are fitted into one another,
as shown in the figure.
Gutzeit‘s Test.—This test is more sensitive to the presence of minute quantities of arsenic than that of either Reinsch or Marsh. The apparatus devised by Dowzard should be used (Journ. Chem. Soc., vols. lxxix. and lxxx. 463, p. 715), which consists of an Erlenmeyer‘s flask fitted with superimposed cells, containing solutions which will wash or neutralise those gases which would interfere with the accuracy of the result. The following is Dowzard‘s description of the method of using the apparatus:
“A weighed or measured portion of the sample is mixed with 5 c.c. of pure HCl (if the sample is alkaline it must be neutralised first), four drops of a 15 per cent. solution of cuprous chloride in hydrochloric acid are then added, and the mixture made up to 30 c.c. with water; if it is not convenient to work with such a small bulk as 30 c.c. this quantity may be doubled or trebled, but the same proportion of acid should be used. A rod of pure zinc, 3 cm. long and 5 mm. in diameter, is first placed in the flask, the above mixture is then introduced and the first cell placed in position; lead acetate solution 5 per cent. is now poured into the cell until it is about half full. The second and third cells are filled in a similar manner; a small tuft of cotton wool is introduced into the neck of the top cell, and its mouth capped with mercuric chloride paper, which may be held in position by an elastic band or a glass collar made from a piece of glass tubing. After forty minutes or more the cap is removed and examined in full daylight. A minute trace of arsenic is indicated by a lemon-yellow spot, which varies in tint according to the amount present; and a heavy trace by an orange-brown spot. The mercuric chloride paper is prepared as follows: one drop of a 5 per cent. solution of mercuric chloride is allowed to fall on the centre of a piece (4 cm. square) of thin Swedish filtering paper, such as Muncktell‘s No. 1 F.; the paper is dried before using.” The lead acetate in the cells absorbs any H₂S gas given off, and if additional cells contain a 15 per cent. solution of cuprous chloride in hydrochloric acid, PH₃ is also prevented from passing and causing a stain. By this method arsenic can be detected in the presence of 2500 times its weight of antimony. The presence of selenium and tellurium compounds does not interfere with the usefulness of this method.
Fleitmann‘s Test.—Detects arsenic in the presence of antimony, but does not detect arsenic as arsenic acid. When zinc or aluminium is heated with excess of potassium or sodium hydroxide in a mixture containing arsenious anhydride, arseniuretted hydrogen is evolved. The gas may be led into 4 per cent. nitrate of silver solution, or a test tube the top of which is covered with filter paper wet with nitrate of silver. The gas reduces the silver salt, and a black precipitate is produced in the solution, or a black spot on the paper.
Fatal Dose.—Two grains in solution have been known to cause death. Recoveries have, however, occurred after an ounce or more of the poison has been taken. Much will depend upon the fulness or emptiness of the stomach at the time the poison is taken, and also upon the vehicle in which the poison is administered. Vomiting and purging are more urgent when the dose is large, probably assisting to get rid of the arsenic before its fatal action is produced.
Fatal Period.—From twenty minutes to two or three weeks, and even later from the secondary effects of the poison. Any thick medium, cocoa or soup, will of course delay the action of the poison.
Treatment.—Vomiting should be promoted, and diluent drinks largely given. The stomach pump, if it can be procured without much delay, should also be employed to empty the stomach. Emetics of sulphate of zinc should be given without delay—followed by the administration of milk, lime-water, and albumen. Symptoms as they occur must be treated on general principles.
The hydrated sesquioxide of iron, the hydrated oxide of magnesia, and animal charcoal have been proposed and used as antidotes. The sesquioxide of iron can be prepared ready to hand by saturating the tincture ferri perchloridi with ammonia or washing soda. It should be given freely. Drachm doses of dialysed iron in water may be administered. Reputed antidotes are useless when the poison is in the solid state. The diarrhœa, tenesmus, collapse, pain, and nervous symptoms should be treated on general principles.
Other Poisonous Compounds of Arsenic
Arsenical Vapour.—The vapour from the flues of the copper and arsenic smelting-works in Cornwall, escaping into the air, may cause death to cattle, and the destruction of vegetation. The workmen in these works not infrequently suffer from eruptions on the skin, and from great constitutional derangement; but, on the whole, taking into consideration the dangerous nature of their employment, the men appear to enjoy average health. Actions for damage and nuisance have resulted from the escape of this vapour from the factories.
Arsenite of Potash.—A solution of arsenite of potash, mixed with the tincture of red lavender (the solution contains four grains of arsenious acid in one ounce)—better known as Fowler‘s Solution, or as Fowler‘s Mineral Solution or Tasteless Ague Drop. It is probably a solution of arsenious acid in carbonate of potash, and not a true arsenite of potash. This preparation has been much used as a domestic remedy for ague in the Fens of Cambridgeshire. Death from its use is rare; but it is, nevertheless, too dangerous a medicine to be used recklessly. Idiosyncrasy has much to do with the action of the drug, some persons taking even large doses with impunity, whilst, in others, the smallest medicinal dose has produced alarming symptoms. It is stated that the Styrian arsenic-eating peasant is capable of taking without injury five grains of arsenious acid for a dose; and in one case of suspected murder in Styria, the prisoner was acquitted as the deceased was known to be an arsenic-eater.
Donovan‘s Solution.—A solution of hydriodate of arsenic and mercury. Now officinal, and much used by many practitioners.
Sheep Dip.—The mixture used for washing sheep, composed of tar-water, soft soap, and arsenic, has caused death in twenty-four hours. The men engaged in dipping the sheep may suffer both locally and constitutionally from the effects of the arsenic in the solution.
Treatment.—As before described.
Analysis.—[See p. 280 et seq.]
Arsenite of Copper.—Scheele‘s green, and the aceto-arsenite of copper, Schweinfurt-green, are met with in commerce and the arts as green pigments. Among workmen they are familiarly known as emerald-green, Brunswick-green, or Vienna-green. In France, the term vert Anglais or English green has been given to them. Scheele‘s green contains about 55 per cent. of pure arsenious acid; the other, Schweinfurt-green, about 58 per cent.
These colours are employed for various purposes, among which the following may be mentioned:
- 1. Artificial flowers and other articles of dress.
- 2. Confectionery, pastry ornaments, and toys.
- 3. As green paint for the insides of houses.
- 4. In the green colour for wall-papers.
- 5. In the green-coloured paper lining boxes, &c.
- 6. Green-coloured tapers used for artificial lighting.
The employment of emerald-green in the colouring of wall-papers is so extensive, that in the year 1860 an English paper-stainer stated that he used two tons of arsenic weekly. In 1862 the amount of this colour manufactured during the year was from 500 to 700 tons. Numerous cases of chronic arsenical poisoning have resulted from the presence of arsenic in the form of Scheele‘s green and Schweinfurt-green in wall-papers and other articles. As the colour is only loosely applied to the surface by means of a weak solution of size, it is easily brushed off, and may so impregnate the air of a room as to produce injurious effects on those who inhabit the apartment. By fermentation of the starch paste used for fastening the paper to the walls, nascent hydrogen is liberated, and, combining with the arsenic to form arseniuretted hydrogen, passes into the air of the room and is inhaled. This gas is extremely poisonous, and small quantities suffice to produce serious results. Certain moulds are endowed with the power of living in materials containing arsenic, and of decomposing arsenious acid or its salts into the gaseous form known as diethylarsine; there are altogether ten such moulds, and the most active is the Penicillium brevicaule.
In the case of ladies‘ dresses, the following method is adopted:
The colouring material is made by thoroughly stirring together a mixture containing, in definite proportions, the green pigment, cold water, starch, and gum arabic, or some similar substance which shall give the colour consistence and adhesiveness. Not infrequently in this process the hand and forearm are freely used in the liquid to expedite the work. Of this mixture, properly prepared, the workman takes a quantity in his fingers and roughly spreads it over the muslin or fine calico. The fabric is then beaten and kneaded between the hands until it is uniformly coloured. The longer this process is continued, the more perfect is the result. The cloth is now fastened to a frame for drying. In all this process of colouring, the hands, forearms, and frequently also the face of the operative must become soiled with the green colour. It will be also observed that the colour is but loosely applied, no mordant being used, as in calico printing, to fix the pigment in the texture of the cloth.
Symptoms.—All the effects produced by arsenic may result from the use of articles coloured with these pigments. Chronic inflammation of the stomach and bowels, and irritation of the eyes, accompanied in some cases with extreme nervous debility and prostration, are by no means uncommon in those employed in the manufacture of this “cheerful,” but poisonous colour. The skin of the hands, arms, and scalp is often attacked by a vesicular eruption or an erythema. When it is borne in mind that, according to the analysis of Hoffman, a single twig of twelve artificial leaves may contain as much as ten grains of pure arsenic, it is not to be wondered at that the most serious results have occurred from the reckless use of these colours. In Prussia and France the use of the arsenical colours is prohibited.
Analysis.—Scheele‘s green is insoluble in water, but is soluble in ammonia, the solution having a blue colour, from the separation of the arsenious acid from the oxide of copper. If a few drops of the blue ammoniacal solution be poured on some crystals of nitrate of silver, the yellow arsenite of silver is formed. The blue ammoniacal solution, if acidified with HCl and boiled with pure copper foil, deposits arsenic on the copper, which, if cut into strips and placed in a small reduction tube and heated, sublimes and is deposited in octahedral crystals on the cold portion of the tube. The tests before described are applicable for the detection of this substance.
Orpiment
Orpiment, or yellow arsenic, one of the sulphurets of arsenic, has been used occasionally as a poison. It is also largely employed in the arts for paper-staining and for colouring toys. In cases of arsenical poisoning, it is this compound that is commonly found adhering to the stomach and intestines. It is formed by the sulphuretted hydrogen, the result of decomposition, acting on the white arsenic swallowed.
Realgar
Realgar, or red arsenic, is another of the sulphurets of arsenic, and, like orpiment, is largely used in the arts as a colour. It is also employed, like orpiment, as a depilatory, fatal results having followed its use for this purpose. The colour of this substance prohibits its frequent use as a poison.
Both of these compounds owe their poisonous properties to the amount of free arsenious acid which they contain, and which may be as much as 30 per cent.
Symptoms.—The symptoms produced by these substances are similar to those caused by arsenic. The fatal dose will depend on the amount of free arsenious acid which they may each contain.
Treatment.—Emetics and demulcent drinks.
Metallic Arsenic, &c.
Metallic arsenic, fly powder, arsenic acid, largely used in the manufacture of magenta, aniline red, or fuchsine, and the arseniates of potash and soda, are all poisonous. The papier moure of the shops consists of blotting-paper steeped in a solution of arseniate of potash. Macquer‘s neutral arsenical salt is the binarsenate of potash.
Symptoms.—The symptoms are those of arsenical poisoning.
Treatment.—When metallic arsenic has been taken, vomiting must be promoted by the use of proper emetics. Tartar emetic should never be used. In the treatment for poisoning with arsenic acid, or of the arseniates of potash and soda, the hydrated oxide of iron, or of the acetate of iron, should be used, as the arseniates are precipitated by the iron.
Arsenic Acid
No case of poisoning by this substance has been recorded, for, although poisonous, it is better known in the laboratory than in the shops. It differs from arsenious acid in being only partially volatilised by heat, in its solubility in water, and in being precipitated of a brick-red colour by nitrate of silver. With sulphuretted hydrogen a yellow precipitate is slowly formed, insoluble in hydrochloric acid.
Arseniuretted Hydrogen
This gas has proved fatal in several cases. It is generated in the process known as Marsh‘s process for arsenic, and is so poisonous that a very small quantity, not sufficient to be detected by its odour, has caused death. In most cases death has been the result of accident.
Symptoms.—Giddiness, fainting, constant vomiting, pain in stomach, and suppression of urine, with rapid destruction of the red blood corpuscles, associated with hæmorrhages from all the mucous membranes and jaundice, are among the most prominent symptoms.
The post-mortem appearances are inflammation of the stomach, with softening of its coats. The liver and kidneys are also more or less affected, and have been found of a deep indigo colour.
Analysis.—This has been described when speaking of Marsh‘s process for arsenic.
Cacodylic Acid
Cacodylic acid and the cacodylates are poisonous. The acid dissolves easily in water and alcohol, and it unites with many metals and organic substances to form salts. Although it is held by some to be non-poisonous, Murrell asserts that the administration of cacodylate of sodium produces symptoms “far more severe than those which follow the exhibition of arsenic in its ordinary forms” (B. M. J., 1900, vol. ii. p. 1823; 1901, vol. i. p. 120).
Professor Fraser of Edinburgh, on the other hand, from clinical observation and chemical tests, affirms that cacodylic acid and the cacodylates are extremely stable bodies, and the arsenic in them is with such great difficulty set free that it passes through the body in combination as an inert substance (B. M. J., 1902, vol. i. p. 713).
Arsenical Contamination of Food Stuffs
Arsenic is found associated with many other substances in nature, particularly copper and pyrites. Arsenic is commonly present in commercial sulphuric acid manufactured from pyrites containing the metal, and when such acid is used with common salt for the production of hydrochloric acid, the latter also becomes contaminated. It may be safely stated that commercial sulphuric acid, hydrochloric acid, copper and zinc, free from arsenic, do not exist in the market. Hence in the detection of arsenic by the toxicologist the absolute purity of these reagents, which he uses, must be established.
In the manufacture of glucose, arseniferous sulphuric acid has been the means of contaminating it. Ritter and Blyth pointed out the danger, by this means, of conveying arsenic into beer, confectionery, syrup, and other food stuffs. Glucose made with such acid, and used in the manufacture of beer, was the cause, in the year 1900, of a widespread and serious epidemic of arsenical poisoning in Manchester and Liverpool, in which several thousand persons suffered. Arsenic may also contaminate grain during malting by the use of anthracite coal or sulphur bar in the kilns.
Recapitulation of the Leading Facts
with regard to Poisoning
with Arsenic