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ARSENIC (symbol As, atomic weight 75.0)
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See also:ARSENIC (See also:symbol As, atomic See also:weight 75.0) , a chemical See also:element, known to the ancients in the See also:form of its sulphides. See also:Aristotle gave them the name o'avoaphKf, and See also:Theophrastus mentions them under the name apteviKbv. The See also:oxide known as See also: Native arsenic occurs usually in metalliferous See also:veins in association with ores of See also:antimony, See also:silver, &c.; the silver mines of See also:Freiberg in See also:Saxony, St Andreasberg in the Harz, and Chanarcillo in See also:Chile being well-known localities. Attractive globular aggregates of well-See also:developed radiating crystals have been found at Akatani, a See also:village in the See also:province Echizen, in See also:Japan. • Arsenic is a constituent of the minerals arsenical See also:iron, arsenical See also:pyrites or See also:mispickel, tin-white See also:cobalt or See also:smaltite, arsenical See also:nickel, See also:realgar, See also:orpiment, pharmacolite and cobalt See also:bloom, whilst it is also met with in small quantities in nearly all specimens of iron pyrites. The See also:ordinary commercial arsenic is either the naturally occurring form, which is, however, more or Jess contaminated with other metals, or is the product obtained by See also:heating arsenical pyrites, out of contact with See also:air, in earthenware retorts which are fitted with a See also:roll of See also:sheet iron at the mouth, and an earthen-See also:ware See also:receiver. By this method of See also:distillation the arsenic sub-limes into the receiver, leaving a See also:residue of iron sulphide in the See also:retort. For further See also:purification, it may be sublimed, after having been previously mixed with a little powdered See also:charcoal, or it may be mixed with a small quantity of See also:iodine and heated. It can also be obtained by the reduction of white arsenic (arsenious oxide) with See also:carbon. An electro-metallurgical See also:process for the extraction of arsenic from its sulphides has also been proposed (See also:German Patent, 67,973). These compounds are brought into See also:solution by means of rwilysulphides of the See also:alkali metals and theresultant liquor run into the See also:cathode compartment of a See also:bath, which is divided by diaphragms into a See also:series of anode and cathode See also:chambers; the anode divisions being closed and See also:gas-tight, and containing carbon or See also:platinum electrodes. The arsenic solution is decomposed at the cathode, and the element precipitated there. Arsenic possesses a See also:steel-grey colour, and a decided metallic lustre; it crystallizes on sublimation and slow condensation in rhombohedra, isomorphous with those of antimony and See also:tellurium. It is very brittle. Its specific gravity is given variously from 5.395 to 5'959; its specific See also:heat is o•o83, and its coefficient of linear expansion x.00000559 (at 4o C.). It is volatile at temperatures above sod° C. and rapidly vaporizes at a dull red heat. It liquefies when heated under pressure, and its melting point lies between 446° C. and 4570 C. The vapour of arsenic is of a See also:golden yellow colour, and has a See also:garlic odour. The vapour See also:density is io•6 (air =1) at 564° C., corresponding to a tetratomic See also:molecule As,; at a white heat the vapour density shows a considerable lowering in value, due to the See also:dissociation of the complex molecule. By condensing arsenic vapour in a See also:glass See also:tube, in a current of an indifferent gas, such as See also:hydrogen, amorphous arsenic is obtained, the See also:deposit on the portion of the tube nearest to the source of heat being crystalline, that farther along (at a temperature of about 210° C.) being a See also:black amorphous solid, while still farther along the tube a grey deposit is formed. These two latter forms possess a specific gravity of 4.710 (14° C.) [A. Bettendorff, Annalen, 1867, 144, p. 110], and by heating at about 358°–36o° C. pass over into the crystalline variety. Arsenic See also:burns on heating in a current of See also:oxygen, with a See also:pale See also:lavender-coloured See also:flame, forming the trioxide. It is easily oxidized by heating with concentrated nitric See also:acid to arsenic acid, and with concentrated sulphuric acid to arsenic trioxide; dilute nitric acid only oxidizes it to arsenious acid. It burns in an See also:atmosphere of See also:chlorine forming the trichloride; it also combines directly with See also:bromine and sulphur on heating, while on See also:fusion with alkalis it forms arsenites. Arsenic and most of its soluble compounds are very poisonous, and consequently the methods used for the detection of arsenic are very important. For full accounts of methods used in detecting See also:minute traces of arsenic in foods, &c., see " See also:Report to See also:Commission to See also:Manchester Brewers' Central Association," the See also:Analyst, 1900, 26, p. 8; " Report of Conjoint See also:Committee of Society of Chemical See also:Industry and Society of Public Analysts," the Analyst, 1902, 27, p. 48; T. E. See also:Thorpe, See also:Journal of the Chemical Society, 1903, 83, p. 774; O. Hehner and others, Journal of Society of Chemical Industry, 1902, 21, p. 94; also See also:ADULTERATION. Arsenic and arsenical compounds generally can be detected by (a) Reinsch's test: A piece of clean copper is dipped in a solution of an arsenious See also:compound which has been previously acidified with pure hydrochloric acid. A grey film is produced on the surface of the copper, probably due to the formation of a copper arsenide. The reaction proceeds better on heating the solution. On removing, washing and gently drying the metal and heating it in a glass tube, a white crystalline sublimate is formed on the cool See also:part of the tube; under the same conditions antimony does not produce a crystalline sublimate. (b) Fleitmann's test and See also:Marsh's test depend on the fact that arsenic and its compounds, when See also:present in a solution in which hydrogen is being generated, are converted into arseniuretted hydrogen, which can be readily detected either by its See also:action on silver nitrate solution or by its decomposition on heating. In Fleitmann's test, the solution containing the arsenious compound is mixed with pure See also:potassium hydroxide solution and a piece of pure See also:zinc or See also:aluminium See also:foil dropped in and the whole then heated. A piece of bibulous See also:paper, moistened with silver nitrate, is held over the mouth of the tube, and if arsenic be present, a grey or black deposit is seen on the paper, due to the silver nitrate being reduced by the arseniuretted hydrogen. Antimony gives no reaction under these conditions, so that the method can be used to detect arsenic in the presence of antimony, but the test is not so delicate as either Reinsch's or Marsh's method. In the Marsh test the solution containing the arsenious compounds is mixed with pure hydrochloric acid and placed in an apparatus in which hydrogen is generated from pure zinc and pure sulphuric acid. The arseniuretted hydrogen produced is passed through a tube containing See also:lead acetate paper and soda-See also:lime, and finally through a narrow glass tube, constricted at various points, and heated by a very small flame. As the arseniuretted hydrogen passes- over 652 the heated portion it is decomposed and a black deposit formed. Instead of heating the tube, the gas may be ignited at the mouth of the tube and a See also:cold surface of See also:porcelain or platinum placed in the flame, when a black deposit is formed on the surface. This may be distinguished from the similar antimony deposit by its ready solubility in a solution of See also:sodium hypochlorite. A See also:blank experiment should always be carried out in testing for small quantities of arsenic, to ensure that the materials used are quite See also:free from traces of arsenic. It is to be noted that the presence of nitric acid interferes with the Marsh test; and also that if the arsenic is present as an arsenic compound it must be reduced to the arsenious condition by the action of sulphurous acid. Arsenic compounds can be detected in the dry way by heating in a tube with a mixture of sodium carbonate and charcoal when a deposit of black amorphous arsenic is produced on the cool part of the tube, or by See also:conversion of the compound into the trioxide and heating with dry sodium acetate when the offensive odour of the extremely poisonous cacodyl oxide is produced. In the wet way, arsenious oxide and arsenites, acidified with hydrochloric acid, give a yellow precipitate of arsenic trisulphide on the addition of sulphuretted hydrogen; this precipitate is soluble in solutions of the alkaline hydroxides, ammonium carbonate and yellow ammonium sulphide. Under like conditions arsenates only give a precipitate on See also:long-continued boiling. Arsenic is usually estimated either in the form of See also:magnesium pyroarsenate or as arsenic sulphide. For the pyroarsenate method it is necessary that the arsenic should be in the arsenic condition, if necessary this can be effected by heating with nitric acid; the acid solution is then mixed with " See also:magnesia mixture " and made strongly alkaline by the addition of See also:ammonia. It is then allowed to stand twenty-four See also:hours, filtered, washed with dilute ammonia, dried, ignited to See also:constant weight and weighed, the See also:filter paper being incinerated separately after moistening with nitric acid. From the weight of magnesium pyroarsenate obtained the weight of arsenic can be calculated. In the sulphide method, the arsenic should be in the arsenious form. Sulphuretted hydrogen is passed through the liquid until it is thoroughly saturated, the excess of sulphuretted hydrogen is expelled from the solution by a brisk stream of carbon dioxide, and the precipitate is filtered on a See also:Gooch crucible and washed with See also:water containing a little sulphuretted hydrogen and dried at loo° C.; it is then well washed with small quantities of pure carbon disulphide to remove any free sulphur, again dried and weighed. Arsenic can also be estimated by volumetric methods; for this purpose it must be in the arsenious condition, and the method of estimation consists in converting it into the arsenic condition by means of a See also:standard solution of iodine, in the presence of a cold saturated solution of sodium bicarbonate. • The atomic weight of arsenic has been determined by many different chemists. J. See also:Berzelius, in 1818, by heating arsenious oxide with excess of sulphur obtained the value 74.3; J. See also:Pelouze (Comptes rendus, 1845, 20, p. 1047) titrated arsenic chloride with silver solution and obtained 75.0; and F. Kessler (Pogg. See also:Ann. 1861, 113, p. 134) by converting arsenic trisulphide in hydrochloric acid solution into arsenic pentasulphide also obtained 75.0.
Compounds.—Arsenic forms two hydrides: The dihydride, As2H2, is a See also: It liquefies at -40° C. and becomes solid at— 118.9° C. (K. Olszewski). Metals such as tin, potassium and sodium, when heated in the gas, form arsenides, with liberation of hydrogen; and solutions of See also:gold and silver salts are reduced by the gas with precipitation of metallic gold and silver. Chlorine, bromine and iodine decompose arsine readily, the action being most violent in the See also:case of chlorine. Arsenic tribromide, AsBra, is formed by the See also:direct See also:union of arsenic and bromine, and subsequent distillation from the excess of arsenic; it forms colourless deliquescent prisms which melt at 20°—25° C., and See also:boil at 220° C. Water decomposes it, a small quantity of water leading to the formation of the oxybromide, AsOBr, whilst a large excess of water gives arsenious oxide, As4O6. Arsenic certainly forms two, or possibly three iodides. The di-iodide, As2I4 or AsI2, which is prepared by heating one part of arsenic with two parts of iodine, in a sealed tube to 230° C., forms dark See also:cherry-red prisms, which are easily oxidized, and are readily decomposed by water. Thelri-iodide, As13, prepared by subliming arsenic and iodine together in a retort, by leading arsine into an alcoholic iodine solution, or by boiling powdered arsenic and iodine with water, filtering and evaporating, forms See also:brick-red hexagonal tables, of specific gravity 4.39, soluble in See also:alcohol, See also:ether and See also:benzene, and in a large excess of water; in the presence of a small quantity of water,it is decomposed with formation of hydriodic acid and an insoluble basic See also:salt of the composition 4AsOI.3As4O6.24H2O. It combines with alkaline iodides to form very unstable compounds. The pentaiodide, AsI5, appears to be formed when a mixture of one part of arsenic and seven parts of iodine is heated to 190° C., but on dissolving the resulting product in carbon bisulphide and crystallizing from this solvent, only the tri-iodide is obtained. Arsenic trichloride, AsCl3, is prepared by distilling white arsenic with concentrated sulphuric acid and See also:common salt, or by the direct union of arsenic with chlorine, or from the action of See also:phosphorus pentachloride on white arsenic. It is a colourless oily heavy liquid of specific gravity 2.205 (0° C.), which, when pure and free from chlorine, solidifies at -18 °C., and boils at 132 °C. It is very poisonous and decomposes in moist air with See also:evolution of white fumes. With a little water it forms arsenic oxychloride, AsOC1, and with excess of water it is completely decomposed into hydrochloric acid and white arsenic. It combines directly with ammonia to form a solid cornpoundvariously givenasAsCI3.3NH3,or2AsC13.7NH3,orAsC13.4NH3. A rsenic trifluoride, AsF3, is prepared by distilling white arsenic with fluorspar and sulphuric acid, or by heating arsenic tribromide with ammonium fluoride; it is a colourless liquid of specific gravity 2.73, boiling at 63° C.; it fumes in air, and in contact with the skin produces painful wounds. It is decomposed by water into arsenious and hydrofluoric acids, and absorbs ammonia forming the compound 2AsF3•5NH3. By the action of gaseous ammonia on arsenious halides at -30° C. to -40° C., arsenamide, As(See also:NH2)a, is formed. Water de-composes it into arsenious oxide and ammonia, and when heated to 60° it loses ammonia and forms arsenimide, As2(NH)3 (C. Hugot, Compt. rend. 1904, 139, p. 54). 
For AsF3, see Ber., 1906, 39, p. 67. Two oxides of arsenic are definitely known to exist, namely the trioxide (white arsenic), As4O6, and the pentoxide, As2O5, while the existence of a suboxide, As2O(?), has also been mooted. Arsenic trioxide has been known from the earliest times, and was called Hiittenrauch (See also:furnace-See also:smoke) by See also:Basil See also:Valentine. It occurs naturally in the See also:mineral claudetite, and can be artificially prepared by burning arsenic in air or oxygen: It is obtained commercially by roasting arsenical pyrites in either a See also:Brunton's or Oxland's rotatory calciner, the crude product being collected in suitable condensing chambers, and afterwards refined by resublimation, usually in reverberatory furnaces, the See also:foreign matter being deposited in a long flue leading to the condensing chambers. White arsenic exists in two crystalline forms (octahedral and prismatic) and one amorphous form; the octahedral form is produced by the rapid cooling of arsenic vapour, or by cooling a warm saturated solution in water, or by See also:crystallization from hydrochloric acid, and also by the See also:gradual transition of the amorphous variety, this last phenomenon being attended by the evolution of heat. Its specific gravity is 3.7; it is only slightly soluble in cold water, but is more soluble in hot water, the solution reacting faintly acid. The prismatic variety of the oxide can be obtained by crystallization from a saturated boiling solution in potassium hydroxide, or by the crystallization of a solution of silver arsenite in nitric acid. Its specific gravity is 4.15. In the amorphous condition it can be obtained by condensing the vapour of the oxide at as high a temperature as possible, when a vitreous See also:mass is produced, which melts at 200° C., has a specific gravity of 3.68—3.798, and is more soluble in water than the crystalline variety. Arsenious oxide is very poisonous. It acts as a reducing See also:agent; it is not convertible into the pentoxide by the direct action of oxygen; and its solution is reduced by many metals (e.g. zinc, tin and See also:cadmium) with precipitation of arsenic and formation of arseniuretted hydrogen. The solution of arsenious oxide in water reacts acid towards See also:litmus and contains tribasic arsenious acid, although on evaporation of the solution the trioxide is obtained and not the free acid. The salts of the acid are, however, very See also:stable, and are known as arsenites. Of these salts several series are known, namely the ortho-arsenites,owhich are derivatives of the acid H3AsO3, the metaarsenites, derivatives of HAsO2, and the pyro-arsenites, derivatives of H4As2O5. The arsenites of the alkali metals are soluble in water, those of the other metals are insoluble in water, but are readily soluble in acids. A neutral solution of an arsenite gives a yellow precipitate of silver arsenite, Ag3AsO3, with silver nitrate solution, and a yellowish-See also:green precipitate (See also:Scheele's green) of cupric hydrogen arsenite, CuHAsO3, with copper sulphate solution. By the action of oxidizing agents such as nitric acid, iodine solution, &c., arsenious acid is readily converted into arsenic acid, in the latter case the re-action proceeding according to the See also:equation H3AsO3+I2+See also:H2O= H3AsO4+2HI. Arsenic pentoxide, As2O5, is most easily obtained by oxidation of a solution of arsenious acid with nitric acid; the solution on concentration deposits the compound 2H3AsO4•H2O (below 15° C.), which on being heated to a dark red heat loses its water of crystallization and leaves a white vitreous mass of the pentoxide. This substance dissolves slowly in water, forming arsenic acid; by heating to redness it decomposes into arsenic and oxygen. It deliquesces in moist air, and is easily reduced to arsenic by heating with carbon. Arsenic acid, H3AsO4, is prepared as shown above, the compound 2H3AsO4•H2O on being heated to loo° C. parting with its water of crystallization and leaving a residue of the acid, which crystallizes in needles. On heating to 18o° C. it loses water and yields pyroarsenic acid, H4As2O7, which at 200° C. loses more water and leaves u crystalline mass of See also:meta-arsenic acid, HAsO3. These latter two acids are only stable in the solid state; they dissolve readily in water with evolution of heat and immediate transformation into the ortho-arsenic acid. The salts of arsenic acid, termed arsenates, are isomorphous with the See also:phosphates, and in See also:general See also:character and reactions resemble the phosphates very closely; thus both series of salts give similar precipitates with " magnesia mixture " and with ammonium molybdate solution, but they can be distinguished by their behaviour with silver nitrate solution, arsenates giving a reddish-brown precipitate,whilstphosphates give a yellow precipitate. There are three known compounds of arsenic and sulphur, namely, realgar As2S2, orpiment As2S3, and arsenic pentasulphide As2S5, Realgar occurs native in See also:orange prisms of specific gravity 3.5; it is prepared artificially by fusing together arsenic and sulphur, but the resulting products vary somewhat in composition; it is readily fusible and sublimes unchanged, and burns on heating in a current of oxygen, forming arsenic trioxide and sulphur dioxide. Orpiment (auri pigmentum) occurs native in pale yellow rhombic prisms, and can be obtained in the amorphous form by passing a current of sulphuretted hydrogen gas through a solution of arsenious oxide or an arsenite, previously acidified with dilute hydrochloric acid. It melts easily and volatilizes. It burns on heating in air, and is soluble in solutions of alkaline hydroxides and See also:carbonates, forming thioarsenites, As2S3+4KHO=K2HAs03+K2HAsS3+H2O. On acidifying the solution so obtained with hydrochloric acid, the whole of the arsenic is reprecipitated as trisulphide, K2HAs03+ K2HAsS3+4H C1=4KCI+3H20+As2S3. Arsenic pentasulphide,As2S5, can be prepared by fusing the trisulphide with the requisite amount of sulphur; it is a yellow easily-fusible solid, which in See also:absence of air can be sublimed unchanged; it is soluble in solutions of the See also:caustic alkalis, forming thioarsenates, which can also be obtained by the action of alkali polysulphides on orpiment. The thioarsenites and thioarsenates of the alkali metals are easily soluble in water, and are readily decomposed by the action of mineral acids. Arsenic compounds containing See also:selenium and sulphur are known, such as arsenic seleno-sulphide, AsSeS2, and arsenic thio-selenide, AsSSe2. Arsenic phosphide, See also:AsP, results when phosphine is passed into arsenic trichloride, being precipitated as a red-brown powder. Many organic arsenic compounds are known, analogous to those of See also:nitrogen and phosphorus, but apparently the See also:primary and secondary arsines, AsH2.See also:CH3 and AsH(CH3)2, do not exist, although the corresponding chlorine derivatives, AsCl2.CH3, methyl arsine chloride, and See also:AsCI(CH3)2, dimethyl arsine chloride, are known. The See also:tertiary arsines, such as As(CH3)3, trimethyl arsine, and the See also:quaternary arsonium iodides and hydroxides, (CH3)4AsI and (CH3)4As•OH, tetramethyl arsonium iodide and hydroxide, have been obtained. The arsines and arsine chlorides are liquids of over-powering smell, and in some cases exert an extremely irritating action on the mucous membrane. They do not possess basic properties; the halogen in the chlorine compounds is readily replaced by oxygen, and the oxides produced behave like basic oxides. The chlorides AsCl2•CH3 and AsCI(CH3)2 as well as As(See also:CH2) 2 are capable of combining with two atoms of chlorine, the arsenic See also:atom apparently changing from the tri- to the penta-valent condition, and the corresponding oxygen compounds can also be oxidized to compounds containing one oxygen atom or two hydroxyl See also:groups more, forming acids or oxides. The compounds of the type AsX5, e.g. AsCl4•CH3, AsCI3(CH3)2, on heating break down, with separation of methyl chloride and formation of compounds of the type AsX3; the breaking down taking See also:place more readily the fewer the number of methyl groups in the compound. The dimethyl arsine (or cacodyl) compounds have been most studied. On distillation of equal parts of dry potassium acetate and arsenious oxide, a colourless liquid of unbearable smell passes over, which is spontaneously inflammable and excessively poisonous. It is sometimes called See also:Cadet's fuming liquid, and its composition was determined by R. See also:Bunsen, who gave it the name cacodyl oxide (uarcc,I c, stinking) ; its formation may be shown thus: As4O6 +8CH3CO2K =2[ (CH3) 2As] 20+4K2CO3+4CO2. The liquid is spontaneously inflammable owing to the presence of free cacodyl, As2(CH3)4, which is also obtained by heating the oxide with zinc clippings in an atmosphere of carbon dioxide; it is a liquid of overpowering odour, and boils at 17o°C. Cacodyl oxide boils at 15o°C., and on exposure to air takes up oxygen and water and passes over into the crystalline cacodylic acid, thus: [(CH3)2As]20+H2O+02 =2(CH3)2As•O.OH. See also:Pharmacology.—Of arsenic and its compounds, arsenious acid (dose 610 gr.) and its preparation liquor arsenicalis, See also:Fowler's solution (dose 2–8 111), are in very common use. The iodide of arsenic (dose - o gr.) is one of the ingredients of See also:Donovan's solution (see See also:MERCURY); and iron arsenate (dose X16 ) gr. in a pill), a mixture of ferrous and ferric arsenates with some iron oxide, is of See also:great use in certain cases. Sodium arsenate (fib- i'r gr.) is somewhat less commonly prescribed, though all the compounds of this metal have great value in experienced hands. Externally, arsenious acid is a powerful caustic when applied 65 3, to raw surfaces, though it has no action on the unbroken skin. Internally, unless the dose be extremely small, all preparations are severe gastro-intestinal irritants. This effect is the same however the See also:drug be administered, as, even after subcutaneous injection, the arsenic is excreted into the See also:stomach after absorption, and thus sets up See also:gastritis in its passage through the mucous membrane. In minute doses it is a gastric stimulant, promoting the flow of gastric juice. It is quickly absorbed into the See also:blood, where its presence can be demonstrated especially in the white blood corpuscles. In certain forms of See also:anaemia it increases the number of the red corpuscles and also their haemoglobin content. None of these known effects of arsenic is sufficient to See also:account for the profound See also:change that a course of the drug will often produce in the condition of a patient. It has some See also:power of affecting the general See also:metabolism, but no wholly satisfactory explanation is forthcoming. According to Binz and See also:Schultz its power is due to the fact that it is an oxygen-See also:carrier, arsenious acid withdrawing oxygen from the See also:protoplasm to form arsenic acid, which subsequently yields up its oxygen again. It is thus vaguely called an alterative, since the patient recovers under its use. It is eliminated chiefly by the urine, and to a less extent by the alimentary See also:canal, sweat, saliva, bile, See also:milk, tears, See also:hair, &c., but it is also stored up in the See also:body mainly in the See also:liver and kidneys. See also:Therapeutics.—Externally arsenious acid has been much used by See also:quack doctors to destroy morbid growths, &c., a See also:paste or solution being applied, strong enough to kill the mass of See also:tissue and make it See also:slough out quickly. But many accidents have resulted from the arsenic being absorbed, and the patient thereby poisoned. Internally it is useful in certain forms of See also:dyspepsia, but as some patients are quite unable to tolerate the drug, it must always be administered in very small doses at first, the quantity being slowly increased as tolerance is shown. See also:Children as a See also:rule See also:bear it better than adults. It should never be given on an empty stomach, but always after a full See also:meal. Certain cases of anaemia which do not yield to iron are often much improved by arsenic, though in other apparently similar ones it appears to be valueless. It is the routine treatment for pernicious anaemia and See also:Hodgkin's disease, though here again the drug may be of no avail. For the See also:neuralgia and anaemia following See also:malaria, for rheumatoid See also:arthritis, for chorea and also See also:asthma and See also:hay See also:fever, it is constantly prescribed with excellent results. Certain skin diseases, as See also:psoriasis, See also:pemphigus and occasionally chronic See also:eczema, are much benefited by its use, though occasionally a too prolonged course will produce the very See also:lesion for which under other circumstances it is a cure. A See also:recent method of using the drug is in the form of sodium cacodylate by subcutaneous injection, and this preparation is said to be free from the cumulative effects sometimes arising after the prolonged use of the other forms. Other organic derivatives employed are sodium metharsenite and sodium anilarsenate or atoxyl; hypodermic injections of the latter have been used in the treatment of sleeping sickness. Occasionally, as among the Styrians, individuals acquire the habit of arsenic-eating, which is said to increase their weight, strength and appetite, and clears their complexion. The probable explanation is that an antitoxin is developed within them. See also:Toxicology and Forensic See also:Medicine.—The commonest source of arsenical poisoning is the arsenious acid or white arsenic, which in one form is white and opaque, like See also:flour, for which it has been mistaken with fatal results. Also, as it has little See also:taste and no colour it is easily mixed with See also:food for homicidal purposes. When combined with potash or soda it is used to saturate See also:fly-papers, and strong solutions can be obtained by soaking these in water; this fact has also been used with criminal See also:intent. Copper arsenite (or Scheele's green) used to be much employed as a pigment for See also:wall-papers and fabrics, and toxic effects have resulted from their use. Metallic arsenic is probably not poisonous, but as it usually becomes oxidized in the alimentary canal, the usual symptoms of arsenical poisoning follow its use. In acute poisoning the See also:interval between the reception of the See also:poison and the onset of symptoms ranges from ten minutes, or even less, if a strong solution be taken on an empty stomach, to twelve or more hours if the drug be taken in solid form and the stomach be full of food. The usual See also:period, however, is from See also:half an See also:hour to an hour. In a typical case a sensation of heat developing into a burning See also:pain is See also:felt in the See also:throat and stomach. This is soon followed by uncontrollable vomiting, and a little later by severe purging, the stools being first of all faecal but later assuming a See also:rice water See also:appearance and often containing blood. The patient suffers from intense thirst, which cannot be relieved, as drinking is immediately followed by rejection of the swallowed fluid. There is profound collapse, the features are sunken, the skin moist and cyanosed. The See also:pulse is feeble and irregular, and respiration is difficult. The pain in the stomach is persistent, and cramps in the calves of the legs add to the See also:torture. See also:Death may be preceded by See also:coma, but consciousness is often maintained to the end. The similarity of the symptoms to those of See also:cholera is very marked, but if the suspicion arises it can soon be cleared up by examining any of the secretions for arsenic. More rarely the poison seems to centre itself on the See also:nerve centres, and gastro-intestinal symptoms may be almost or quite absent. In such cases the acute collapse occurs in See also:company with both superficial and deep See also:anaesthesia of the limbs, and is soon followed by coma terminating in death. In criminal poisoning repeated doses are usually given, so that such cases may not be typical, but will present some of the aspects of acute and some of chronic arsenical poisoning. As regards treatment, the stomach must be washed out with warm water by means of a soft See also:rubber tube, an emetic being also administered. Then, if available, freshly precipitated ferric See also:hydrate must be given, which can be prepared by adding a solution of ammonia to one of iron pet-chloride. The precipitate is strained off, and the patient can See also:swallow it suspended in water. While this is being obtained, magnesia, See also:castor oil or See also:olive oil can be given; or failing all these, copious See also:draughts of water. The collapse must be treated with hot blankets and bottles, and subcutaneous injections of See also:brandy, ether or See also:strychnine. The pain can be lessened by injections of morphia. Arsenic may be gradually absorbed into the system in very small quantities over a prolonged period, the symptoms of chronic poisoning resulting. The commonest See also:sources used to be wall-papers, fabrics, artificial See also:flowers and toys: also certain trades, as in the manufacture of arsenical See also:sheep-dipping. But at the present See also:time cases arising from these causes occur very rarely. In 1900 an outbreak of " peripheral See also:neuritis " with various skin affections occurred in See also:Lancashire, which was traced to See also:beer made from See also:glucose and invert See also:sugar, in the preparation of which sulphuric acid contaminated with arsenic was said to have been used. But the nature of the disease in this case was decidedly obscure. The symptoms so closely resembled those of See also:ben-ben that it has also been suggested that the illness was the same, and was caused by the manufacture of the glucose from mouldy rice (see BE11-BExl), though no See also:proof of this was possible. The earliest symptoms are slight gastric disorders, loss of appetite and general malaise, followed later by colicky pains, irritation of eyelids and skin eruptions. But sooner or later peripheral neuritis' develops, usually beginning with sensory disturbances, tingling, numbness, formication and occasionally cutaneous anaesthesia. Later the affected muscles become exquisitely See also:tender, and then See also:atrophy, while the See also:knee-jerk or other reflex is lost. Pigmentation of the skin may occur in the later stages. Recovery is very slow, and in fatal cases death usually results from See also:heart failure. After acute poisoning, the stomach at a See also:post-mortem presents signs of intense inflammation, parts or the whole of its mucous membrane being of a colour varying from dark red to See also:bright See also:vermilion and often corrugated. Submucous haemorrhages are usually present, but perforation is rare. The See also:rest of the alimentary canal exhibits inflammatory changes in a somewhat lesser degree. After chronic poisoning a widely spread fatty degeneration is present. Arsenic is found in almost every part of the body, but is retained in largest amount by the liver, secondly by the kidneys. After death from chronic poisoning it is found present even in the See also:brain and spongy See also:bone. The detection of arsenic in criminal cases is effected either by Reinsch's test or' by Marsh's test, the urine being the secretion analysed when available. But Reinsch's test cannot be used satisfactorily for a quantitative determination, nor can it be used in the presence of See also:chlorates or nitrates. And Marsh's test is very unmanageable with organic liquids on account of the uncontrollable frothing that takes place. But in such cases the organic matter can be first destroyed by one of the various methods, usually the moist method devised by See also:Fresenius being chosen. Additional information and CommentsThere are no comments yet for this article.
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