COPPER.

distinguishing test for the metal.

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The best test is yellow prussiate of potash, which gives a brown precipitate when the metal is present even in very minute quantity.

Dinoxide, suboxide, red oxide, Cu,O 9, native in octahedrons. It may be prepared by boiling a solution of sulphate of copper with starch or sugar, and caustic potash or soda; the red oxide subsides, or it is formed by fusing chloride of copper with carbonate of soda, or by heating protoxide with copper filings. Specific gravity 6. Absorbs oxygen at a red heat, and becomes black oxide. Dilute acids convert it into metallic copper, and a salt of the protoxide; dissolves in ammonia; colours glass red.

Cupric acid, Cu, 03. - Dissolve 20 grains of black oxide in 70 grains nitric acid, of specific gravity 1.35. Then 50 grains fresh hydrate of lime are mixed with one pound solution of bleaching powder, specific gravity 1.06, and added to the solution of copper. A precipitate of a purplish black gradually subsides, which is washed with cold lime water. It is nearly black, but when placed in a thin layer on glass it is rose. (Crum.)

Nitret, Cu N, a green powder, formed by passing dry ammonia over protoxide, turning at 570°, into nitrogen and copper. Chlorides. — There are two chlorides; the dichloride, a brown powder, Cu, Cl, formed by heating corrosive sublimate (Hg Cl) with copper; and the chloride, Cu Cl, green needles, obtained by dissolving copper in hydrochloric acid: this salt above 400° is converted into dichloride by losing half its chlorine.

Disulphuret, Cu, S, copper glance, a rich ore of copper found in Cornwall and South Australia. Copper unites with various metals, forming alloys. Brass consists of 3 parts of copper and 1 of zinc, and sometimes of 4 and 5 parts of copper to one of zinc. It is more fusible than copper; ductile; pinchbeck or similor consists of equal parts of the two metals, and possesses a golden colour: hence the name. Bronze, and the metal of cannon consist of 9 parts of tin and 91 of copper. The strength of bronze of this composition is to malleable iron as 1 to 2. Bell metal is also formed of copper and tin in different proportions; but a common proportion is 3 copper to 1 tin. of telescopes consist of 2 copper to 1 tin. Tinned pans are copper pans covered with a layer of tin in the inside, to prevent the contents from acting on the copper. The copper pan is first rubbed over with salammoniac, heated; pitch is thrown into it, and a piece of tin rubbed over the copper surface.

Mirrors

China silver or tutenag consists of copper, zinc, and nickel. The same substances enter into the composition of Britannia metal and German silver. Spoons and forks of this description should not remain in contact with acid, sauces, or pickles.

Carbonate of copper, CuO CO2, blue and green, according to the quantity of water present, occurs in nature, and admits of

a fine polish, when it is known as malachite. Nitrate of copper, CuO NO,, 3HO in prisms, or with 6HO in rhomboids, is obtained by dissolving metallic copper in nitric acid. When ignited, black oxide of copper remains. When moistened and rolled up in tinfoil, heat and light are given out, and peroxide of tin formed. Sulphate of copper, CuO SO, 5HO, blue doubly. oblique prisms, obtained by dissolving copper in SO, and crystallizing. It is used as an emetic in cases of poisoning, and as a caustic for sores under the name of bluestone. Acetate of copper, or verdigris, one of the cheapest salts of copper, formed by acting on copper with cloth dipped in vinegar, is used for preparing Scheele's green by mixture with arsenious acid.

FINE white metal, softer than copper, harder than gold, crystallizes in octahedrons. Specific gravity 10·474; very malleable and ductile; 1 grain may be drawn out 400 feet; melts when completely red hot, or at 1830°.

Reduction. Silver is separated from lead when it occurs in the ores of that metal by oxidation, as stated under lead, when the ore occurs in the metallic state. It is treated with mercury, and the amalgam distilled; the mercury passes over and leaves the silver. Pure silver is obtained by dissolving silver in nitric acid, precipitating by hydrochloric acid, and fusing the washed chloride with twice its weight of carbonate of potash mixed with some nitre and pounded rosin in a clay crucible. The silver collects in a button at the bottom. Silver is separated from gold by dissolving the mixture in SO,. The gold remains as in Chinese silver.

Oxide, AgO 14.5, grayish powder, obtained by precipitating nitrate of silver by caustic soda. Specific gravity 7.143. It combines with ammonia, forming an explosive compound, and is dissolved by an excess. The oxide does not form a hydrate. When the salts of this oxide in solution are mixed with mercury in a glass vessel, the silver is deposited in the form of a tree, called the Tree of Diana (Arbor Dianæ). The experiment may be made by dissolving 15 grains of nitrate of silver in half a wine glass-full of water, adding a few globules of mercury, and allowing the glass to stand at rest for some hours. The permanent ink, commonly sold for marking linen, contains in one bottle caustic soda or carbonate of soda, and in the other a solution of nitrate of silver. The spot to be marked is first moistened with soda, dried, and then written on with a pen dipped in the silver solution. The oxide is precipitated. The

salts of the oxide of silver are colourless, have a metallic taste, and are poisonous; the antidote being common salt. Copper, zinc, and mercury precipitate silver from its solutions. Ammonia redissolves the oxide when precipitated. Dinoxide, Ag2O. The oxide of silver contained in citrate of silver loses only half its oxygen under the action of hydrogen gas, a suboxide being formed which forms a dark brown solution. Peroxide is deposited on the positive pole of a galvanic battery, in a solution of nitrate of silver in needles.

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Chloride of Silver, Ag Cl, 18, Horn Silver, Luna Cornea, obtained by precipitating a solution of lunar caustic (AgO NO) with H Cl, or common salt. A white curdy precipitate; when moist, insoluble in nitric acid; when dry becoming purple and black melts at 500°, and forms a horny mass, soluble in ammonia; crystallizes in octahedrons. When moist it may be converted into oxide by boiling with caustic soda and the addition of a little pounded rosin. The silver may be reduced by boiling the chloride in an iron pot with water. Specific gravity 5.55. Iodide of Silver, Ag I 29.25. Yellow powder, formed by dropping iodide of potassium into nitrate of silver. Cyanide, Ag Cy 16.75, white curdy precipitate, resembling the chloride, but distinguished from it by its solubility when boiled with nitric acid. This is used for procuring hydrocyanic acid in medicine. Trisphosphate of Silver, 3 AgO PO5, yellow powder, obtained by precipitating nitrate of silver by the common phosphate of soda. Diphosphate or Pyrophosphate, 2AgO PO,, white powder, from the mixture of ignited phosphate of soda with a soluble salt of silver. Nitrate of Silver, Lunar Caustic, Lapis Infernalis, AgO NO, 2125 in plates, obtained by dissolving pure silver in NO,, and evaporating cautiously to drive off excess of acid. Used as a reagent and caustic. For the latter purpose it is fused and poured into tubes, where it solidifies. When free from organic matter it retains its colour, but if it has touched paper it becomes dark coloured. When heated it is partially converted into nitrite.

Alloys of Silver. English silver coin contains copper; the quantity in a shilling, which weighs 87.2727 grains, is 6.5455 grains of alloy; or, in 12 ounces of standard silver, the copper amounts to 18 dwt., or 1 copper to 12 silver; 1 lb. Troy yielding 66 shillings. French silver coin consists of 1 copper, 10 silver; Dutch, 1 copper to 11 silver; Russian, 1 to 3; Hamburg, equal parts.

Estimation. Silver is always estimated in the form of chloride of silver; every 18 parts of which contain 13 of metallic silver. It is best to precipitate silver by common salt, as the chloride is somewhat soluble in HCl.

These metals melt below a red heat. They are all precipitated in the metallic state from their solutions by zinc; and the others, by those above them, in the order in which they stand.

ZINC. Zn 4.125.

Characters. Brilliant blueish white metal, rather soft, tinging the fingers black. Specific gravity when melted 7°; when hammered 7.81; melts at 680°, and distils at a white heat. At 400° it can be pounded. When cooled slowly it crystallizes in 4-sided prisms. It is found in nature in the state of blende, Black jack or sulphuret (Zn S), and as calamine or carbonate of Zinc (Zn O CO2).

Process. The metal is reduced by heating the ore along with small coal, in clay pots or crucibles. The metal drops through a hole in the bottom of each pot, by an iron tube, into a vessel of water. It is used for roofs, for milk dishes, chimney pots, &c. Oxide, Zn O 5.125. Zinc tarnishes in the air by uniting with a small portion of oxygen. Water is decomposed by the hot metal. When zinc is strongly heated in an open clay crucible it takes fire, burns with a white flame, and gives out abundant white flocks of oxide (Philosophic wool). It may also be prepared by precipitating any of the salts of zinc, as the sulphate, by an alkaline carbonate, washing and igniting the white carbonate; oxide of zinc remains, which is yellow when hot, white when cold. It is tasteless, soluble in ammonia and caustic alkalies, and can thus be separated from iron.

Chloride of zinc, Zn Cl 8.625, gray, solid, deliquescent; formed by dissolving zinc in hydrochloric acid, and igniting gently. It may be sublimed, when it crystallizes in needles. It is used as a caustic, also to preserve wood and cordage, and as a disinfecting agent.

Sulphate of zinc, Zn O SO, 7 HO, prisms obtained in the preparation of hydrogen by acting on zinc with dilute sulphuric acid; used in the proportion of 1, 2, or 3 grains to an ounce of water, as an eyewater, in inflammation: it acts also as an emetic. It forms with sulphate of potash a double salt; the potash salt replacing one atom of water, Zn O SO,, KO SO, 6 HO. Magnesia, manganese, &c. form similar double salts.

Carbonate of zinc, Zn O CO2, Zinc spar, Calamine, the common ore of zinc, a yellowish solid. The precipitated carbonate consists of a mixture of carbonate and hydrate of the oxide. (2 Zn O CO2, 3 Zn O HO.)

Galvanised An alloy is

Zinc is usually To separate it

A plate of zinc precipitates lead from its solution. iron is obtained by plunging iron into melted zinc. formed on the surface, which prevents oxidation. estimated by boiling with carbonate of soda. from nickel it is necessary to precipitate both metals by an alkaline carbonate, to dissolve the carbonate in acetic acid, and pass a current of sulphuretted hydrogen through the solution, Zn S is precipitated, while the nickel remains in solution.

CADMIUM. Cd. 7.

Characters. A whiter metal than zinc, with which it is generally associated. Fracture hackly, crystallizes on cooling in octahedrons, soft and easily cut, ductile specific gravity 8.7, melting point 4420, rising into vapour above 600°. Process. It may be separated from zinc by caustic soda, in which it is insoluble, or by carbonate of ammonia, which, in excess, dissolves zinc, but not cadmium; the oxide thus obtained may be reduced in the same way as zinc. A plate of zinc precipitates metallic cadmium. Oxide, Cd 08. Čadmium burns in the air like zinc, forming a brownish yellow smoke of oxide. The oxide may be obtained pure by precipitation from its salts by soda or carbonates. It is a yellow powder. The Sulphuret is yellow, and acts as a paint while that of zinc is white. The two metals may thus be easily distinguished. The sulphuret (Cd S) occurs native in the form of a beautiful mineral-Greenockite. The Chloride is a rectangular prism.

LEAD. Pb 13 (Plumbum).

Characters. A blueish white metal, staining the fingers and paper, and cutting soft, with a fine lustre; specific gravity 11.35, not increased by hammering; very malleable, and capable of being formed into thin plates, not very ductile. Melting point 606°; at a white heat it boils and evaporates; on cooling, crystallizes in octahedrons. Process. It is reduced from the sulphuret of lead (PbS) or galena, a mineral which occurs in cubes with a metallic lustre, by roasting it to convert the sulphur into sulphuric acid, the ore becoming PbO SO,, and then fusing the sulphate with coal and lime; the metal is extricated, while carbonic acid escapes and sulphuret of lime is left: if it contains silver, the lead is oxidized, and the silver remains. Lead forms