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[As colour is various shades of green, yellow, and brown. Its primitive form is a rhomboid, but it usually occurs in six-sided prisms. It is semi-transparent and brittle.

897. Carbonate of Lead. When an alcaline carbonate is added to nitrate of lead, a white precipitate of carbonate of lead falls: it is tasteless, insoluble in water, but soluble in fixed alcaline solutions. It is employed as a white paint, under the name of white lead or ceruse, and is usually prepared by exposing sheet lead to the action of the vapour of vinegar. The process is described in AIKIN'S Dictionary, (Art. LEAD.) It consists of 112 oxide of lead + 22 carbonic acid = 134 carbonate of lead.

898. Native Carbonate of Lead is one of the most beautiful of the metallicores: it occurs crystallized and fibrous, the former transparent, the latter generally opaque. It is soft and brittle, and occasionally tinged green with carbonate of copper, or grey by sulphuret of lead. The octoëdron is its primitive form: it also occurs prismatic and tabular. It has been found in Cumberland and Durham, and the acicular variety of great beauty in Cornwall.

899. Ferrocyanate of potassa produces a white precipitate when added to the soluble salts of lead.

900. Borate of Lead is precipitated in the form of a white powder, when borate of soda is mixed with nitrate of lead.

Characters of

901. The soluble salts of lead have a sweetish austere taste, and are characterized by the white precipitate produced by ferrocyanate of po-the salts of tassa, the deep brown by hydrosulphuret of ammonia, and the yellow lead, by hydriodate of potassa.

The salts insoluble in water are dissolved by soda and potassa, and by nitric acid, when the metal is rendered manifest by sulphuretted hydrogen and other tests. Heated by the blowpipe upon charcoal They afford a button of metal.

902. The Alloys of Lead with the preceding metals are not important, we except that which it forms with tin. Common pewter consists of About 80 parts of tin and 20 of lead, Equal parts of lead and tin constiCute plumbers' solder; and what is termed pot-metal is an alloy of lead and copper.

903. In analyzing these alloys, 100 grains in filings may be boiled to dryness in two ounces of nitric acid, water poured upon the residue, and filtered; the peroxide of tin remains in the filter, and the nitrate of lead, which passes through in solution, may be converted into sulphate by adding sulphate of soda. 152 grains of sulphate of lead dried at a red heat, indicate 104 of metal; and 75 grains of washed peroxide of tin are equivalent to 59 grains of metallic tin.

904. With potassium lead forms a brittle and very fusible alloy; with sodium the compound is equally brittle but less fusible. When exposed to air these alloys suffer decomposition in consequence of the ⚫xidizement of the alcaline bases. The alloy of Lead and Manganese has not been examined. When lead is fused with iron two alloys are obtained; that at the bottom of the crucible consisting of lead with a .ttle iron; while the superficial portion is iron with a little lead (GurJS MORVEAU, Ann. de Chim., lvii.) With zinc, lead forms a hard Mectile alloy.

Reduction of

ore.

SECTION XV. Antimony.

905. THIS metal is found native in Sweden, in France, and in the Hartz; but its principal ore is the sulphuret which is found massive and crystallized, and of which there are several varieties. The most common is the radiated, which is of a grey colour, brittle, and frequently crystallized in four and six-sided prisms. This ore may be decomposed, and the pure metal obtained from it, by the following process: Mix three parts of the powdered sulphuret with two of crude tartar, and throw the mixture by spoonfuls into a red-hot crucible; then heat the mass to redness, and a button will be found at the bottom of the crucible, which is the metal as it commonly occurs in commerce, and is nearly pure. Reduce this button to fine powder, and dissolve it in nitro-muriatic acid; pour this solution into water, which will occasion the precipitation of a white powder, which is to be washed and mixed with twice its weight of tartar and exposed to a dull red heat in a crucible. The button now obtained is pure antimony.

906. Antimony is of a silvery white colour, brittle, and crystalline in its ordinary texture. It fuses at about 800, and is volatile ata high heat. Its specific gravity is 6.712. (HATCHETT, Phil. Trans., 1803.) Placed upon ignited charcoal, under a current of oxygen gas, antimony burns with great brilliancy, throwing off its oxide in the form of a dense yellow smoke.

907. Antimony and Oxygen. -These bodies form two well-defined compounds, the history of which is of great importance to the pharmaceutical chemist.

The Protoxide of Antimony is thus obtained: To 200 parts of sulphuric acid add 50 parts of powdered metallic antimony. Boil the mixture to dryness, wash the dry mass, first in water, and then with a weak solution of carbonate of potassa; a white powder remains, which when thoroughly washed with hot water, is Protoxide of Antimony. It may also be procured by dissolving antimony in muriatic acid, pouring the solution into water, and washing the white precipitate with weak solu tion of potassa.

908. This oxide may also be obtained by adding ammonia to solution of tartrate of antimony and potassa, heating the mixture and washing the precipitate in large quantities of boiling water. It is thus procur ed in the form of a heavy white powder. This process is directed in the Pharmacopeia.

This protoxide exists in all the active antimonial preparations; in emetic tartar, kermes, glass of antimony golden sulphuret, &c. It is fusible and volatile at a red heat: decomposed by sulphur and charcoal and when acted on by nitric acid, is converted into peroxide. If heated with chlorate of potassa it deflagrates and also becomes peroxidized; it is very soluble in muriatic acid, and readily forms emetic tartar when boiled in solution of tartrate of potassa.

When metallic antimony in fusion is exposed to a bright red heat, is converted into an oxide which appears to be the protoxide, and which condenses in long and delicate needles when sublimed. It was formely called argentine flowers of antimony.

909. Peroxide of Antimony is procured by acting for a considerable

time upon the powdered metal, by excess of hot nitric acid, and exposing the product to a red heat. The diaphoretic antimony and Bezoar mineral of old Pharmacopaiæ consisted of this oxide, which compared with the protoxide is nearly inert.

910. Peroxide of antimony is also formed by exposing the metal or the protoxide mixed with five or six parts of nitre to a red heat, in a porcelain crucible, and washing the residue with hot water. It is yellowish white, but becomes buff-coloured when heated, and returns to its former tint on cooling. It neither fuses nor volatilizes at a bright red heat, but when exposed to the flame of a spirit-lamp urged by a blow-pipe, it passes off slowly in white fumes, being partially reduced by the hydrogen of the flame.

911. Berzelius (Ann. de Chim., lxxxvi. 225), has described four oxides of antimony; but it is probable that the first and the fourth are not distinct compounds: they are said to be constituted as follows:

1 Suboxide consisting of 100 antimony + 4.65 oxygen.

2 Oxidule

100

+18.60......

...

[blocks in formation]

The two last oxides are called by Berzelius, stibious and stibic acids,

or antimonious and antimonic acids.

The second and fourth are probably the oxides described in paragraphs 908 and 909, but their composition is by no means satisfactorily

ascertained.

912. Native Oxide of Antimony is occasionally found incrusting the native metal and the sulphuret.

913. I have found by experiment that the oxygen in the protoxide (908) is to that in the peroxide (909) as 1 to 2; and if we consider these as the second and fourth oxide described by Berzelius, we obtain the number 40 as the representative of antimony. Dr. John Davy's researches on the composition of the chlorides, (Phil. Trans., 1812,) give the number 42.5 as the representative of antimony; and this nearly agrees with my own experiments upon the composition of the proLoxide, (obtained by precipitation from emetic tartar), which give 45, and which I shall therefore adopt.

The protoxide of antimony will then consist of
Antimony 48 + Oxygen 8 =56*.

And the peroxide will be composed of

Antimony 48 + Oxygen 16 = 64.

914. The acid properties of peroxide of antimony were long since remarked by Thenard, (Ann. de Chim., xxxviii. and xli.) and the subject has lately been investigated by Berzelius, who obtained it by exposing a mixture of one part of powdered antimony and six of nitre to

• 45 is merely altered to 48 in order to be proportional to 8 instead of 7.5 oxygen. The great discrepancy in the results of different Chemists makes it improper to offer any num** confidently. Brand gives his own the preference, although it does not agree with the

of Dr. D. any better than the 40 stated in his text.

MM

a red heat in a silver crucible for an hour. After washing off the soluble matters by cold water, and digesting the white powder which remains in muriatic acid, washing and drying it at a red heat, it is pure antimonic acid, and consists of antimony 100, oxygen 37.2.

915. Antimoniate of Ammonia is formed by digesting the acid in ammonia. On evaporation a superantimoniate of ammonia is obtained in the form of a white powder.

916. Antimoniate of Potassa is contained in the white powder obtained by igniting nitre and antimony. (919). It dissolves in hot water. and this solution produces precipitates of insoluble antimoniates in se veral other metallic solutions.

Our knowledge of the composition and properties of the oxides of antimony, and of most of their combinations, is still extremely imperfect, and the whole subject requires further investigation before the anomalies that now present themselves can be cleared up.

917. Antimony and Chlorine combine in one proportion only to produce the chloride of antimony. The powdered metal takes fire when thrown into the gas, and a compound, at first liquid, but afterwards concreting, is formed. It may also be produced by the distillation of one part of powdered antimony with two and a half of bi-chloride of mercury; or by dissolving the protoxide of antimony in muriatic acid, and evaporating to dryness. It consists of 48 A. + 36 C. The pure chloride is a soft solid at common temperatures, but becomes liquid by a gentle heat, and crystallizes as it cools. It is the butter of antimony of old writers. It deliquesces by exposure to air; and is a powerful caustic. When water is added to the chloride of antimony, a mutual decomposition ensues, and hydrated protoxide of antimony, formerly called Algarotti's powder, or mercurius vitæ, and muriatic acid result. 918. Chlorate of Antimony has not been examined. 919. Iodide of Antimony is of a dark red colour; acted upon by water, it produces hydriodic acid and oxide of antimony. 920. Iodate of Antimony is unknown.

921. Nitric acid acts powerfully on metallic antimony, and if mixed with it in fine powder, will sometimes cause its inflammation. The metal becomes peroxidized, and scarcely an appretiable portion is retained in solution. As in some other cases of the vehement decomposition of nitric acid, ammonia is produced, (287) which may be rendered sensible by pouring potassa on the white magma that results.

Protoxide of antimony, digested in dilute nitric acid, produces a dith cultly soluble salt, which separates in white scaly crystals, and which appears to be a nitrate of antimony, but I have not particularly examin

ed it.

922. Nitro-muriatic acid readily dissolves antimony, and forms an orange-coloured solution, which is decomposed by the addition of wa ter. Iron or zinc immersed into this solution throws down a black pow der, which, according to Thenard, is pyrophoric.

923. Sulphuret of Antimony is easily formed by fusing the metal with sulphur. It consists of 48 A. + 16 S. Its colour is dark grey and metallic. Its specific gravity 4.36. It closely resembles the native sulphuret (905.)

924. When the native sulphuret is exposed under a muffle to a dul red heat, it gradually loses sulphur and absorbs oxygen, being convert ed into a grey powder, which consists of a mixture of protoxide of antamony and sulphuret. If the heat be increased, this fuses into a transparent substance of a yellow or brown colour, formerly called glass of Glass of antiantimony. Its composition is variable; it generally contains about 85 mony. per cent. of protoxide and 15 of sulphuret. In that which is imported for pharmaceutical purposes, from Germany and Holland, there is usually a portion of siliceous earth, and it is sometimes adulterated with oxide of lead. This fraud is easily detected by digesting the finely powdered glass in hot nitric acid, diluting the solution and filtering. The filtered liquor gives a white precipitate on the addition of sulphate of soda if lead were present.

During the formation of glass of antimony, if the heat be raised too high the greater part of the protoxide sublimes in slender crystalline needles; while another portion, if air be not excluded, passes into the state of peroxide, and undergoes no change at a very high temperature. Compounds of the protoxide with larger quantities of the sulphuret have been termed saffron of antimony or crocus metallorum, and liver of ontimony.

925. Neither the Hyposulphite nor the Sulphite of antimony are

known.

926. Sulphate of Antimony. - When sulphuric acid is boiled upon finely-powdered antimony, the metal is oxidized, and an acid sulphate and a subsulphate of antimony are the results. In both these salts the metal is in a state of protoxide. (907.)

927. Hydrosulphuretted Oxide of Antimony. - This compound has long been known under the name of kermes mineral; it is commonly prepared as follows: Equal parts of sulphuret of antimony and common potash are fused together; the resulting mass is finely powdered and boiled in ten times its weight of water. The liquor is filtered while hot; and, during cooling, it deposits kermes. The mother liquor of kermes deposits a copious yellowish red precipitate upon the addition of dilute sulphuric acid, which, when washed and dried, is known under the name of golden sulphur of antimony. In the London Pharmacopeia it is called antimonii sulphuretum præcipitatum.

In forming these compounds, the following changes seem to have taken place. The sulphuret of antimony and potassa act upon the water, a portion of which is decomposed; hydrogen is transferred to the alcaline sulphuret, to form hydrosulphuret of potassa; hydrogen and oxygen unite to the sulphuret of antimony, producing a hydrosulphuretted oxide of that metal (kermes), which remains dissolved in the hot alcaline hydrosulphuret, and of which one portion is precipitated as that solution cools. When dilute sulphuric acid is added, the hydrosulphuret of potassa is decomposed, sulphate of potassa is formed, and sulphur and sulphuretted hydrogen are liberated; the sulphur falls in combination with the kermes, producing the golden sulphur, or sulphuretted hydrosulphuret.

928. Phosphuret of Antimony is formed by heating together equal parts of oxide of antimony, phosphoric acid, and charcoal. It is white and

brittle.

929. Nothing is known respecting either the Hypophosphite or the Phosphite of antimony.

930. Phosphate of Antimony has not been formed: in the London Pharmacopeia there is a preparation called pulvis antimonialis, formed by heating one part of sulphuret of antimony with two of hartshorn

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