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MERCURY (symbol Hg, atomic weight = 2oo)
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See also:MERCURY (See also:symbol Hg, atomic See also:weight = 2oo) ,'in See also:chemistry, a metallic See also:element which is easily distinguished from all others by its being liquid at even the lowest temperatures naturally occur-See also:ring in moderate climates. To this exceptional See also:property it owes the synonyms of quicksilver in See also:English (with the Germans Quecksilber is the only recognized name) and of hydrargyrum (from ii&ap, See also:water, and ap'yvpos, See also:silver) in Graeco-Latin. This See also:metal does not appear to have been known to the See also:ancient See also:Jews, nor is it mentioned by the earlier See also:Greek writers. See also:Theophrastus (about 300 B.C.) mentions it as prepared from See also:cinnabar by treatment with See also:copper and See also:vinegar; Dioscorides obtained it from the same See also:mineral with the aid of See also:iron, employing at the same See also:time a See also:primitive See also:distillation apparatus. With the alchemists it was a substance of See also:great consequence. Its See also:appearance commended it as a substance for investigation; many of its compounds, especially corrosive sublimate and See also:calomel;; were' studied, and improved methods for extracting and purifying the metal were devised. Being ignorant of its susceptibility of freezing into a compact solid, they did not recognize it as a true metal, and yet, on the authority of See also:Geber, they held that mercury (meaning the predominating element in this metal) enters into the See also:composition of all metals, and is the very cause of their metallicity (see ELEMENT). When, about the beginning of the 16th See also:century, chemistry and scientific See also:medicine came to See also:merge into one, this same mysterious element of " mercury " played a great See also:part in the theories of See also:pathology; and the metal, in the See also:free as in certain combined states, came to be looked upon as a powerful medicinal See also:agent. Occurrence.—Mercury occurs in nature chiefly in the See also:form of a red sulphide, HgS, called cinnabar (q.v.), which, as a See also:rule, is accompanied by more or less of the reguline metal—the latter being probably derived from the former by some secondary reaction. The most important mercury mines in See also:Europe are those of See also:Almaden in See also:Spain and of See also:Idria in See also:Illyria; and in See also:America those of See also:California and See also:Texas. Deposits also occur in See also:Russia, the Bavarian See also:palatinate, in See also:Hungary, See also:Italy, Transylvania, Bohemia, See also:Mexico, See also:Peru and in some other countries. Mercury occurs in formations of all ages from the Archean to the See also:Quaternary, and it has been found in both sedimentary and eruptive rocks of the most varied See also:character, e.g. conglomerates, sandstones, shales, limestones, quartzites, slates, serpentines, crystalline See also:schists, and eruptive rocks from the most See also:acid to the most basic. It appears that nearly all known deposits occur along lines of See also:continental uplift, where active shearing of the formations has occurred. Large deposits are seldom found in eruptive rocks, but generally near such formations or near active or See also:extinct hot springs. The deposits are of many types, See also:simple fissure See also:veins being less usual than See also:compound, reticulated, or linked veins. Segregations and impregnations are very See also:common. The form of the See also:deposit seems to depend chiefly on the See also:physical properties and structure of the enclosing rocks and the nature of the fissure systems that result from their disturbance. The See also:principal ore is cinnabar, though metacinnabarite and native mercury are often abundant; the selenide (tiemannite), chloride, and iodide are rare. Of the associated heavy minerals, pyrite (or See also:marcasite) is almost universal, and chalcopyrite, See also:tetrahedrite, See also:blende and See also:realgar are frequent. Many deposits contain traces of See also:gold and silver, and some deposits, as the Mercur in See also:Utah, are more valuable for their gold than their mercury content. The usual See also:gangue-forming minerals are See also:quartz, See also:dolomite, See also:calcite, barite, fluorspar and various See also:zeolites. Some form of bituminous See also:matter is one of the most universal and intimate associates of cinnabar. Formerly quicksilver deposits were supposed to be formed by sublimation, but from a careful study of the California occurrences S. B. See also:Christy was convinced as See also:early as 1875 that this was unlikely, and that deposition from hot alkaline sulphide solutions was more probable. By treating the See also:black mercuric sulphide with such solutions, hot and under pressure, he succeeded in producing artificial cinnabar and metacinnabarite. He also showed that the mineral water at the New Almaden mines, when charged with sulphydric acid and heated under pressure, was capable of effecting the same See also:change, and that this method of See also:production agreed better with all the facts than the sublimation theory. (See " See also:Genesis of Cinnabar Deposits," Amer. Jour. See also:Science, xvii. 453.) The investigations of Dr G. F. See also:Becker on the " Quicksilver Deposits of the Pacific " (U.S. Geol. Survey, Mon. xiii., 1888) established the correctness of these views beyond doubt. Production.—At one time the See also:world's See also:supply of mercury was almost entirely derived from the Almaden and Idrian mines; but now the greater proportion is produced in California and Texas, where cinnabar was used by the See also:Indians as a pigment, and first turned to metallurgical purpose in 1845 by Castellero. In the See also:United States mercury has also been found in Utah, See also:Nevada, See also:Oregon and See also:Arizona. In the 16th century the Almaden and Idrian mines were practically the only producers of this metal; See also:statistics of Almaden dating from 1564 and of Idria since 1525 are given in B. See also:Neumann, See also:Die Metalle (1904). Spain produced 1151 metric tons in 1870, and in 1889 its maximum of 1975 tons; since then it has, on the whole, been decreasing. The See also:Austria-Hungary output steadily increased to about 550–600 tons at which it appears to remain. In 1887 Russia produced 64 tons, and has steadily improved. The United States output was over moo tons, in 1871, and declined to 8o0–900 in the See also:period 1889–1892; it has since increased and surpassed the supply from Spain. The following table gives the production in various countries for selected years: : United years: Spain. States. Russia. Austria- Hungary. Italy. Mexico. T ns). See also:Total etrc 1901 754 1031 368 558 278 128 3120 1902 1425 1208 416 556 259 191 4056 03 914 1288 362 L19 04 1020 I192 393 581 357 1901 3733 05 Soo 1043 318 567 564 314 370 188 3633 1901 3285 Estimated. Mercury is transported in See also:steel bottles closed by a See also:screw stopper; the Almaden and Idrian bottles contain 76 lb; and until the 1st of See also:June 1904, the Californian bottles contained 762 lb of mercury; they now hold 75 lb. From the smaller See also:works the metal is sometimes sent out in sheepskin bags holding 55 lb of mercury. Metallurgy.—Chemically speaking, the extraction of mercury from its ores is a simple matter. Metallic mercury is easily volatilized, and separated from the gangue, at temperatures far below redness, and cinnabar at a red See also:heat is readily reduced to the metallic See also:state by the See also:action of iron or See also:lime or atmospheric See also:oxygen, the See also:sulphur being eliminated, in the first See also:case as iron sulphide, in the second as See also:calcium sulphide and sulphate, in the third as sulphur dioxide. A See also:close iron See also:retort would at first suggest itself as the proper See also:kind of apparatus for carrying out these operations, and this See also:idea was; at one time, acted upon in a few small establishments—for instance, in that of See also:Zweibrucken in the Palatinate, where lime was used as a decomposing agent; but the method has now been discarded. In all the large works the decomposition of the cinnabar is effected by the See also:direct exposure of the ore to the oxidizing See also:flame of a See also:furnace, and the mercury vapour, which gets diffused through an immense See also:mass of See also:combustion gases, is recovered in more or less imperfect condensers. With the exception of the massive deposits of Almaden in Spain and a few of those in California and Idria, cinnabar occurs in forms so disseminated as to make its See also:mining very expensive. See also:Rude See also:hand-sorting of the ores is usually practised. Wet concentration has not been successful, because it necessitates ore crushing and extensive slime losses of the brittle cinnabar. As a rule See also:low-grade ores can be roasted directly with less loss and expense. At Almaden in Spain the ores See also:average from 5 to 7 %, but in other parts of the world much poorer ores have to be treated. In California, in spite of the high cost of labour, improved furnaces enable ores containing not more than i % to be See also:mined and roasted at a profit. The furnaces originally used at Almaden and Idria differ only in the condensing plant. The roasting was carried out in internally fired, See also:vertical shafts of See also:brickwork, and, at Almaden, the vapours were led through a See also:series of bottles named aludels, so arranged that the See also:neck of one entered the See also:sole of the next; and at Idria the vapours were led into large brickwork See also:chambers lined with See also:cement, and there condensed. The aludel furnace, which was designed in 1633 by See also:Lopez See also:Saavedra Barba in See also:Huancavelica, Peru (where cinnabar was discovered in 1566), and introduced at Almaden in 1646 by Bustamente, by whose name it is sometimes known, has now been entirely given up. The Idrian furnace was designed in 1787 by von Leithner; it was introduced at Almaden in 1800 by Larrafiaga, and used See also:side by side with the aludel furnace. The crude mercury is purified by straining through dense See also:linen or See also:chamois See also:leather bags. The most important improvements in the metallurgy of mercury are the introduction of furnaces for treating coarse ores, and the replacement of the old discontinuous furnaces by those which See also:work continuously. The most successful of these continuous furnaces was a modification of See also:Count See also:Rumford's continuous lime-See also:kiln. This furnace was introduced at New Almaden by J. B. Randol, the author of many improvements in the metallurgy of mercury. The success of the continuous coarse-ore furnace at New Almaden led Randol to See also:attempt the continuous' treatment of See also:fine ores also, and the Huettner and See also:Scott continuous fine-ore furnace, which was the result of these experiments solved the problem completely. It contains several vertical shafts in which the descending ore is retarded at will by inclined shelving, which causes it to be exposed to the flames as See also:long as may be necessary to roast it thoroughly. The time of treatment is determined by the rapidity with which the roasted ore is withdrawn at the bottom. Several similar furnaces are in use, as the See also:Knox and See also:Osborne, the See also:Livermore and the Cormak-Spirek. The fumes from the roasting furnaces are received in See also:masonry chambers, usually provided with water-cooled pipes; from these they pass through earthenware pipes, and finally through others of See also:wood and See also:glass. Not all the yield is in liquid mercury; much of it is entangled in masses of See also:soot that See also:cover the See also:condenser walls, and this is only recovered after much labour. The conditions for effective condensation are: (1) The furnace gases should be well oxidized, to avoid the production of an excess of soot. See also:Gas firini would meet this requirement better than the use of wood or See also:coal. (2) The See also:volume of permanent gases passing thro h the furnace should be reduced to a minimum consistently wit See also:complete oxidation. (3) The See also:cross-See also:section of the condensers should be sufficient to reduce the velocity of the escaping gases, and the See also:surface large enough for cooling and for the See also:adhesion of condensed mercury. The latter requirement is best provided for by See also:hanging wooden aprons in the path of the cooled gases. (4) The temperature of the escaping gases should not exceed 15° to 20° C., but cooling below this temperature would not give any adequate return for the expense. Cooling by water is quicker, but more expensive than by See also:air. Water sprays, acting directly on the fumes, have not given See also:good results, on See also:account of the difficulty of recovering " floured " quicksilver from the water. (5) The use of an artificial inward See also:draught is absolutely necessary to See also:control the operation of the furnaces and condensers and to avoid the salivation of the workmen. (6) The condenser should be easily and quickly cleaned, during the operation of the furnace. (7) Both furnaces and condensers should have inclined iron plates in their See also:foundations to prevent the infiltration of mercury. (8) There is a great need of some substance for the construction of quicksilver condensers which shall be strong enough to be made thin, be a good conductor of heat, and resistant to See also:abrasion and the alternate action of heat and See also:cold. It should also resist the action of mercury and warm dilute sulphuric acid, and be not too expensive. ,1Quicksilver is best removed from the " soot," not by pressure, but ky the opposite treatment. A See also:machine in use for this purpose at New Almaden, devised by See also:Colonel von Leicht, consists of an iron bowl, perforated at the bottom, in which revolves a vertical See also:shaft carrying a propeller blade which tosses the soot (mixed with wood ashes and a little coal oil) into the air, so that the entangled mercury is free to run out through the bottom of the bowl. The See also:residue from which no more mercury can be extracted mechanically is returned to the roasting furnace. The losses of treatment are: (I) Furnace loss, which is easily reduced to nothing, and (2) condenser loss, which can never be zero. The latter consists of mercury lost as vapour and as mist, and its minimum amount is determined not by the richness of the ore but by the volume of escaping gases, their velocity and temperature. The percentage of loss will be higher with a poor than a See also:rich ore. On a 3 % ore the losses need not exceed 3 or 4 % ore content. On a I % ore they will run from 5 to 10 %. But in poorly arranged See also:plants under See also:bad management they may easily be doubled or even trebled. The Huettner and Scott fine-ore furnace See also:costs with condensers in California about $30,000, and roasts from 30 to 45 tons of ore (from 2; in. to dust) in 24 See also:hours at a cost of from $I to $o•62 per ton. See also:Purification.—Commercial mercury, as a rule, only needs to be forced through chamois leather or allowed to run though a very fine hole to become See also:fit for all See also:ordinary applications; but the metal, having the See also:power of dissolving most other metals, is very liable to get contaminated, and requires then to be purified. For this purpose many chemical methods have been proposed; the commonest consist in allowing the metal to fall in a very fine stream through a See also:column of a mixture of nitric acid and mercurous nitrate, or of sulphuric acid, or of See also:potassium bichromate and sulphuric acid; the metal being subsequently dried and filtered through a perforated See also:paper See also:filter. The only 'really exhaustive method is distillation in a vacuum out of a glass apparatus. Many forms of apparatus have been devised to effect this. See also:Recent researches have shown, however, that the metal so obtained is not chemically pure, there being found in the distillate traces of other metals. Absolutely pure mercury does not at all adhere to any surface which does not consist of a metal soluble in mercury. Hence the least quantity of it, when placed on a See also:sheet of paper, forms a neatly rounded-off globule, which retains its form on being rolled about, and, when subdivided, breaks up into a number of equally perfect globules, which tend to coalesce when sufficiently near to each other. The presence in it of the minutest trace of See also:lead or See also:tin causes it to " draw tails." A very impure metal may adhere even to glass, and in a glass See also:vessel, instead of the normal See also:convex, form an irregular See also:flat meniscus.
Properties.—Pure mercury is a freely flowing liquid, which does not wet See also:objects placed in it, and has a silvery See also: Mercury is unattacked by dilute sulphuric acid; the strong acid, however, dissolves it on See also:heating with the formation of sulphur dioxide and mercurous or mercuric sulphate according as mercury is in excess or not. Hydrochloric acid has no action. Dilute nitric acid readily attacks it, mercurous nitrate being formed in the cold with excess of mercury, mercuric nitrate with excess of acid, or with strong acid, in the warm. The metal dissolves in solutions containing See also:chlorine or See also:bromine, and consequently in aqua regia.
Mercury readily dissolves many metals to form a class of compounds termed amalgams, which have considerable applications in the arts.
Compounds of Mercury.
Mercury forms two well-defined series of salts—the mercurous salts derived from the oxide Hg2O, and the mercuric salts from the oxide HgO; the existence of these salts can hardly be inseparably connected with a variable See also:valency, i.e. that mercury is monovalent in mercurous, and divalent in mercuric compounds, for according to See also:Baker mercurous chloride or calomel (q.v.) has the See also:formula Hg2C12.
Mercurous Oxide, Hg20, is an unstable dark-See also: Mercurous and mercuric chlorides, known respectively as calomel (q.v.) and corrosive sublimate (q.v.), are two of the most important salts of mercury. Mercurous bromide, Hg2Br2, is a yellowish-white powder, insoluble in water. Mercuric bromide, HgBr2, forms white crystals, sparingly soluble in cold water, readily in hot, and prepared by the direct See also:union of its components. Mercurous iodide, Hg2I2, is a yellowish-See also:green powder obtained by heating its components to about 250°, or by triturating them with a little See also:alcohol; it is also obtained by precipitating a solution of mercurous nitrate with potassium iodide. It is blackened by exposure to light. Mercuric iodide, HgI2, exists in two crystalline forms. By mixing solutions of mercuric chloride and potassium iodide under a See also:microscope, yellow rhombic plates are seen to be formed which are transformed very quickly into See also:scarlet quadratic octahedra. On heating to about 126° the red form is transformed into the yellow modification; on cooling the See also:reverse gradually occurs, and immediately if the yellow iodide be touched. Mercuric iodide is insoluble in water, but soluble in See also:absolute alcohol; and also in potassium iodide solution, with the formation of K2HgI4, which may be obtained in See also:lemon-yellow crystals. A strongly alkaline solution of this salt is known as Nessler's reagent, and is specially used for determining traces of ammonia (see below). Mercuric iodide dissolves in other iodide solutions to form similar compounds; these solutions are characterized by their exceptionally high specific gravity, and hence are employed in density determinations (see DENSITY). It also forms many other See also:double salts. Oxidation with strong nitric acid gives the iodate, Hg(IOa)i. An iodide, Hgsla, intermediate between mercurous and mercuric iodides, is obtained as a yellow insoluble powder by precipitating mercurous nitrate with a solution of See also:iodine in potassium iodide. Mercurous fluoride, Hg2F2, and mercuric fluoride, HgF2, are unstable substances obtained from the corresponding oxide and hydrofluoric acid. Mercurous Nitrate, Hg2(NOs)2 . 2H2O, is obtained as a white crystalline salt soluble in water by dissolving the metal in cold dilute nitric acid; if the metal be in excess a basic salt Hg2(NOs)2 . 2HG20, 3H2O is obtained. Several other basic salts are known. By adding ammonia to a solution of mercurous nitrate a black precipitateof variable composition, known in See also:pharmacy as mercurius solubilis Hahnemanni, is obtained. Mercuric Nitrate.—By dissolving mercuric oxide in strong nitric acid there is obtained a thick liquid which will not crystallize, and which gives on the addition of strong nitric acid a white precipitate of 2H (NO2)2 . See also:H2O. Water decomposes it to give basic salts of variable composition. By dissolving the oxide in dilute nitric acid, the basic salt Hg(NOa)2 . HgO . H2O, crystallizing in needles, is obtained. Mercurous Sulphide, Hg2S, is an unstable black powder obtained by acting with sulphuretted hydrogen, diluted with carbon dioxide, on calomel at -Id°. It decomposes into mercuric sulphide and mercury at o°. Mercuric sulphide, HgS, is one of the most important mercury compounds; it is the principal ore, occurring in nature as the mineral cinnabar (q.v.), and is extensively used as a pigment, See also:vermilion (q.v.). It is obtained as a black powder by triturating mercury with sulphur, the compound thus formed being known in pharmacy as Aethiops mineralis, and also by precipitating a mercuric salt with sulphuretted hydrogen. It is only slightly acted upon by nitric acid; it dissolves in aqua regia; chlorine gives a yellow compound, 2HgS . HgC12i and it dissolves in potassium sulphide solutions to form double salts of variable composition. Mercurous Sulphate, Hg2SO4, is a white, sparingly soluble, crystal-See also:line substance obtained by adding See also:sodium sulphate to a solution of mercurous nitrate. Mercuric sulphate, HgSO4, is a white, soluble salt obtained by dissolving mercury in hot strong sulphuric acid; on digestion with water, it decomposes into a basic salt HgSO4. 2HgO known as turbith or turpeth mineral, and into an acid salt, HgSO4 . 2SO3. Mercury Phosphide, Hg3P2, is obtained as brilliant red, hexagonal crystals by heating mercury with See also:phosphorus iodide to 300 and removing the mercuric iodide simultaneously formed by means of potassium iodide solution. Mercurous phosphate, Hg3PO4, and mercuric phosphate, Hg3(PO4)2, are obtained as white precipitates by adding sodium phosphate to solutions of mercurous and mercuric nitrates respectively. Mercurammonium Compounds.—By the action of ammonia and ammonium salts mercury compounds yield a number of substances, many of which have long been used in medicine. By the action of dry ammonia on calomel mercuroso-ammonium chloride, NH3HgCI, is obtained; aqueous ammonia on calomel gives dimercuroso-ammonium chloride, NH2Hg2C1. By adding ammonia to a solution of mercuric chloride, mercurammonium chloride, known in pharmacy as " infusible white precipitate," NH2HgCI, is obtained; " fusible white precipitate " is mercuro-diammonium chloride, Hg(NH3C1)2, and is obtained by adding a solution of mercuric chloride to hot solutions of ammonium chloride and ammonia so long as the precipitate first formed redissolves; the substance separates out on cooling. By precipitating a strongly alkaline solution of mercuric iodide in potassium iodide (Nessler's solution) there is obtained a yellow"irecipitate of NH2Hg2OI; this reaction is the most delicate test for ammonia, a yellow coloration being given by See also:minute traces. By passing dry ammonia over precipitated mercuric oxide at 130°, a nitride N2Hg3 is obtained. The oxide and ammonia solution gives the See also:stable and basic mercurhydroxylamine, NHg2OH. The constitution of these compounds has been especially studied by K. A. See also:Hofmann and E. C. See also:Marburg (Zeit. Anorg. Chem. 23, p. 126) ; these chemists formulate " infusible precipitate " as Hg(See also:NH2)Cl, ' fusible precipitate " as Ilg(NH4Cl)2 Millon's See also:base " as (HO . H )2:NH2OH, thus postulating three distinct types of compounds, (i) amidochlorides; (2) See also:amines; (3) substituted ammonium derivatives. See also:Analysis.—Mercury compounds, when heated in a closed See also:tube with sodium carbonate, yield a See also:grey to black sublimate of metallic mercury, which readily unites to form visible globules. The metal is precipitated from solutions by digestion with bright copper-See also:foil, a coating being formed on the copper, which becomes silvery on rubbing, and disappears when the quicksilvered copper is heated in` a sublimation tube. Solutions of mercurous salts with hydrochloric acid give a white precipitate of calomel, which becomes See also:jet-black on treatment with ammonia. Stannous chloride, in its twofold capacity as a chloride and a reducing agent, precipitates both mercurous and mercuric solutions, at first as calomel, and on addition of an excess of reagent the precipitate becomes grey through-See also:conversion into finely-divided quicksilver. Sulphuretted hydrogen, when added very gradually to an acid mercuric solution, gives at first an almost white precipitate, which, on addition of more and more reagent, assumes successively a yellow, orange and at last jet-black colour. The black precipitate is HgS, which is identified by its great heaviness, and by being insoluble in boiling nitric and in boiling hydrochloric acid. A mixture of the two (aqua regia) dissolves it as chloride. " Mercurous " mercury is quantitatively estimated by precipitating as calomel and weighing the precipitate on a tared filter at See also:loo°. The metal may also be estimated by distillation in a closed tube with lime, the metal being collected and weighed, or by precipitating the solution with an excess of stannous chloride. More convenient is the method of precipitating as sulphide by an excess of sulphuretted hydrogen, and weighing the precipitate on a tared filter; or by means of a See also:Gooch crucible. See also:Pharmacology and See also:Therapeutics The use of mercury as a therapeutic agent is of comparatively recent date. To the Greeks and See also:Romans its value was unknown, and the Arabian physicians only used it for skin affections. It was not till the See also:middle of the 16th century that the See also:special properties of mercury were fully appreciated, but since that time the metal has continued to hold a high though fluctuating value as a medicine. At first the metal in a finely divided state or in vapour was used; but very soon its various compounds werefound to be endowed with See also:powers even greater than those of the metal itself, and with the discovery of new compounds the number of See also:mercurial medicines has largely increased. The See also:British Pharmacopeia contains some twenty-five mercurial preparations, including those of calomel (q.v.). Only the useful preparations will be mentioned here. Free mercury is contained 1n Hydrargyrum cum Creta, or " grey powder," which consists of one part of mercury to two of prepared See also:chalk. The power of this valuable and widely used preparation varies somewhat with its See also:age, as old specimens contain some mercuric oxide, which makes them more active. The dose is 1–5 gr., and the preparation is usually employed for See also:children. The Pilula Hydrargyri, or " See also:blue pill, usually contains one part of mercury in three, and the dose is 4–8 gr. It is usually employed for adults. There are also five preparations of free mercury for See also:external use. Of these the most useful is the Unguentum Hydrargyri, " or blue ointment," which contains one part of mercury in two. Weaker ointments are also prepared from the red and the yellow forms of mercuric oxide. The perchloride of mercury or corrosive sublimate is therapeutically the most important salt of mercury. The dose is 212--?.g gr. It is incompatible with alkalies, alkaline See also:carbonates, potassium iodide, albumen and many other substances, and should therefore be prescribed alone. It is decomposed by impure water, and distilled water is therefore used in making the Liquor Hydrargyri Perchloridi, in which form it is usually prescribed. This contains half a See also:grain of the perchloride to the fluid See also:ounce and its dose is 3o–6o minims. The perchloride is also compounded with lime-water to form the Lotio Hydrargyri Flava, or ' yellow See also:wash," which contains two grains of the salt to the fluid ounce. Mercuric iodide is an equally potent salt and has come into wide use of See also:late years. It has the same dose as the perchloride and is largely prescribed in the Liquor Arsenii et Hydrargyri Iodidi, or See also:Donovan's solution, which contains i % of arsenious iodide and i % of mercuric iodide, the dose being 5–20 minims. An ointment widely used is prepared from the mercurammonium chloride (Unguentum Hydrargyri ammoniatum) of which it contains one part in ten. It is known as " white precipitate ointment." In discussing the pharmacology of mercury and its compounds, it is of the first importance to observe that metallic mercury is inert as such, and that the same may practically be said of mercurous salts generally. Both mercury itself and mercurous salts tend to be converted in the See also:body into mercuric salts, to which the action is due. When metallic mercury is triturated or exposed to air it is partly oxidized, the first See also:stage of its transformation to an active See also:condition being thus reached. Metallic mercury can be absorbed by the skin, passing in minute globules through the ducts of the sweat-glands. The mercury contained in " blue ointment " is certainly thus absorbed, actually circulating in the See also:blood in a very different form, as described below. There is no See also:local action on the skin. The mercuric salts, and especially the chloride and iodide, are probably the most powerful of all known See also:antiseptics. One part of the perchloride in 500,000 will prevent the growth of See also:anthrax bacilli, and one part in 2000—the strength commonly employed in See also:surgery—kills all known bacteria. The action is apparently specific and not due to the fact that per-chloride of mercury precipitates albumen, including the albuminous bodies of bacteria, for the iodide is still more powerful as a germicide, though it does not coagulate albumen. These salts cannot be employed for sterilizing metallic See also:instruments, which they tarnish. As these drugs are essentially poisons they must be used with the greatest care in surgical practice, and as they are particularly deleterious to the secreting structure of the See also:kidney they must not be employed as antiseptics in diseases where renal inflammation is already See also:present or probable. They are therefore contra-indicated for application to the See also:throat in scarlet-See also:fever or to the uterus in eclampsia. The stronger mercurial ointments kill cutaneous parasites and also possess some degree of antipruritic action, especially when the cause of the itching is somewhat obscure. Mercuric salts, when in strong solution, are caustic. It is important to observe .that the volatility of metallic mercury and many of its compounds causes their absorption by the lungs even when no such effect is intended to follow their external application. This fact explains the occurrence of chronic mercurial poisoning in certain trades. Single doses of mercury or its compounds have no action upon the mouth, the characteristic salivation being produced only after many doses. Their typical action on the bowel is purgative, the effecaa, varying with the state of the mercury. So relatively inert is metallic mercury that a See also:pound of it has been given without See also:ill effects in cases of intestinal obstruction, which it was hoped to relieve by the See also:mere weight of the metal. Half a grain of the perchloride, on the other hand, is a highly toxic dose. The action of mercurials on the bowel is mostly exerted on the duodenum and jejunum, though the See also:lower part of the bowel is slightly affected. Hence a dose of mercury usually needs a saline aperient to complete its action, as in the " blue pill and black draught " of former days. Mercurials do not cause, in therapeutic doses, much increase in the intestinal secretion, the action being mainly exerted on the See also:muscular See also:wall of the bowel. The bile is rapidly removed from the duodenum, before any re-absorption can occur, and the bacterial action which
decomposes the bile-pigment is arrested by the antiseptic power of the See also:drug, so that the excreta are of a very dark colour. The classical experiments of See also: The See also:excretion of the drug is accomplished by all the secreting glands, including the breasts, if these are functioning. All the secretions of the body, except that of the peptic glands of the See also:stomach, are stimulated, but the excretion of mercury is slow, and it is typically one of the drugs that are cumulative, like See also:arsenic and See also:digitalis. Mercury is largely used in affections of the alimentary See also:canal, and has an obscure but unquestionable value in many cases of See also:heart-disease and arterial degeneration. But its value in syphilis (see VENEREAL DISEASES) far outweighs all its other uses. See also:Toxicology.—Acute poisoning by mercurials usually occurs in the case of corrosive sublimate. There is intense gastro-intestinal inflammation, with vomiting, frequent " See also:rice-water " stools and extreme collapse. The treatment, except when the case is seen at once, is very difficult, but white-of-See also:egg or other form of albumen is the antidote, forming an insoluble compound with the perchloride. Chronic poisoning (hydrargyrism or mercurialism) is of great importance, since any indication of its symptoms must be closely watched for in patients who are under mercurial treatment. Usually the first symptom is slight tenderness of the See also:teeth whilst eating, and some foetor of the breath. These symptoms become more marked and the gums become the seat of severe inflammation, being spongy, vascular and prone to bleed. The salivary glands are swollen and See also:tender, and the saliva pours from the mouth,'and may amount to pints in the course of a See also:day. The teeth become quite loose and may fall out. The symptoms are aggravated until the See also:tongue and mouth ulcerate, the See also:jaw-See also:bone necroses, haemorrhages occur in various parts of the body, and the patient See also:dies of anaemia, septic inflammation or exhaustion. The treatment consists, besides stopping the intake of See also:poison and relieving the symptoms, in the See also:administration of potassium iodide in small, often repeated doses. Additional information and CommentsThere are no comments yet for this article.
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