Part 118
II. _Calcination._ This operation is accomplished in several kinds of furnaces, that used by the Tharsis Sulphur and Copper Company, being a large muffle or close furnace. By others a patent furnace with a revolving hearth and mechanical stirring arrangement has been adopted with good results; and some use open reverbatory furnaces heated by gas from Siemens's generators. During the roasting the mixture is frequently stirred, and in the case of hard-worked furnaces, turned with long rabbles, and the completion of the operation is ascertained by test assays. When the copper has been brought into a soluble condition, the charge is raked out of the furnace and permitted to cool under a screen at its mouth. By the calcination the sulphur in the compound is first oxidised, sulphate of sodium is formed, and at the same time the chlorine from the sodium chloride unites with the copper to form cupric chloride. A small proportion of cuprous chloride is also formed, and special precautions have to be taken to prevent the extensive formation of this compound which is dissolved only with difficulty. The hydrochloric acid and other gaseous products evolved during the calcination are condensed as 'tower liquor' in ordinary condensing towers, and the product is used in the subsequent process of lixiviation.
III. _Lixiviation._ The calcined ore is conveyed to tightly caulked wooden tanks, in which it receives repeated washings with hot water, tower liquor, and dilute hydrochloric acid till all the soluble copper is thereby extracted. The product of the latter washings is pumped or drawn up by a modification of Gilford's injector, to serve as a first liquor for subsequent charges of the lixiviating tanks, and no solution under a definite strength is permitted to pass on to the next stage in the process. The insoluble residue in the tanks consist of "purple ore," an almost pure ferric oxide, largely used in "settling" blast furnaces, and for smelting purposes; besides which it is available as jewellers' rouge.
IV. _Precipitation._ The precipitation of metallic copper from the solution of its chloride is accomplished in large tanks by means of metallic iron in the same way that cementation copper is obtained from solutions of the sulphate. The solution is run into the tanks in which there are miscellaneous heaps of old malleable iron; the chlorine combined with the copper unites with the iron, and metallic copper in the state or fine division is thrown down. The completion of the precipitation is ascertained by dipping a bright steel knife into the solution in the tank, and when no deposit of copper covers the steel, the liquor is run off and a new charge conveyed into the tank. The tanks are drained periodically for removing the precipitate, which is first roughly separated from the small pieces of iron, after which it is more thoroughly freed from iron, &c., by washing in water in a rocking sieve apparatus. The precipitate so obtained should contain 80 per cent. of metallic copper, which is either smelted directly for blister copper, or may be fused with the white metal of the ordinary smelting process, and subsequently roasted. It has been found possible to extract in this process with profit the small proportions of lead, silver and gold, which Spanish pyrites is known to contain. Two processes are in operation for this purpose--one devised by Mr P. Claudet, and the other by Mr W. Henderson, the original patentee of the wet process. The liquors from the first three washings contain practically, all these metals, and they alone are treated. Mr Claudet precipitates them from the solution by means of iodide of potassium. Mr Henderson dilutes his solution from 20° to 25° Twaddell, and adds a very weak solution of lead salt, such as the acetate by which he obtains a cream-coloured precipitate containing 5 or 6 per cent. of silver, and 3 oz. of gold to each ton of the precipitate. The importance of the wet process may be estimated from the fact, that although it originated only in 1860, already 14,000 tons of copper, are annually produced by it in Great Britain alone, out of an annual production for the whole world estimated at from 126,000 to 130,000 tons.
_Prop., &c._ Copper has a brilliant yellowish-red colour, a nauseous, styptic taste, and emits a disagreeable odour when rubbed; is very malleable and ductile; unchanged in dry air; in damp air it soon becomes covered with a greenish rust (carbonate of copper); slightly soluble in dilute sulphuric and hydrochloric acid; freely soluble in boiling oil of vitriol (sulphurous anhydride being evolved); dilute nitric acid dissolves it readily with copious evolution of nitric oxide; heated to redness in the air, it rapidly becomes covered with a black scale (oxide); it fuses at a full red heat; its crystals are either octahedra or dodecahedra; sp. gr. 8·8 to 8·96; it forms numerous compounds (alloys and salts) with other bodies, all of which are more or less poisonous; its salts are either blue or green, and most of them (when neutral) are soluble in water.
_Tests._ Metallic copper may be recognised by the above properties; its oxides, salts, &c., by the following characters and reactions:--The solutions of copper possess a blue or green colour, which they retain even when considerably diluted with water:--With caustic potassa they give a light-blue, bulky precipitate, turning blackish-brown or black on boiling the liquid:--Ammonia and carbonate of ammonium produce a bluish-white precipitate, soluble in excess, yielding a rich deep-blue solution:--The carbonates of potassium give a light precipitate, insoluble in excess:--Ferrocyanide of potassium gives a reddish-brown precipitate:--Sulphuretted hydrogen and sulphydrate of ammonium give blackish-brown or black ones:--A polished rod of iron, on immersion in an acidulated solution, quickly becomes coated with metallic copper.
_Estim., &c._ Copper is generally WEIGHED under the form of black oxide, but sometimes as pure metal:--By throwing it down from its solution by pure potassa, after which it must be carefully collected, washed, dried, ignited in a platinum crucible, and weighed therein as soon as it is cold. Every 5 parts of the ignited precipitate (oxide) represents 4 parts of copper (nearly); or, more accurately, every 39·7 parts are equal to 31·7 of pure metallic copper:--By immersing a piece of polished steel in the solution, and weighing the resulting precipitate of the copper (see _above_). Less delicate than the preceding.
Copper can be separated from the other metals by means of the following processes:--
From lead. By adding sulphuric acid to the nitric solution, and evaporating to dryness, when water digested on the residuum will dissolve out the sulphate of copper, but leave the sulphate of lead behind. From this solution the oxide of the copper may be thrown down as before.
From tin. By digestion with hot nitric acid, which dissolves out the tin.
From zinc. By sulphuretted hydrogen, which throws down the sulphide of copper from an acid solution.
From silver. By digesting it in the state of filings or powder in a solution of chloride of zinc, which dissolves the first, but leaves the last unchanged.
Copper may be separated, in a state of great purity, from ANTIMONY, ARSENIC, BISMUTH, LEAD, IRON, TIN, ZINC, &c., as it exists in bell-metal, brass, bronze, gun-metal, mosaic gold, and other commercial alloys, by fusing it in a crucible for about half an hour, along with copper scales (black oxide) and ground bottle-glass, or other like flux. The pure metal is found at the bottom of the crucible, whilst the impurities are either volatilised or dissolved in the flux. The proportions for refining commercial copper are, metal, 10 parts; copper scales and bottle-glass, of each 1 part. The Society of Arts conceived this process to be so valuable, that they presented one of their gold medals to its inventor, Mr Lewis Thompson.
_Uses, &c._ The ordinary uses of copper are well known. In _medicine_, 3 or 4 gr. of the filings or powder were formerly given in rheumatism, and to prevent hydrophobia. Some of its salts are still used as astringents, emetics, and caustics. Its alloys are of great value. With zinc it forms BRASS; with tin, BRONZE, BELL-METAL, GUN-METAL, and SPECULUM-METAL. WHITE COPPER is formed by the addition of metallic arsenic, and GERMAN SILVER is a mixture of nickel, zinc, and copper.
_Ant._ Copper in the metallic state is almost inert, but all its compounds are poisonous. The antidotes are--the white of egg, milk, or flour, mixed with water. The hydrated sulphides of iron, iron filings, and ferro-cyanide of potassium have also been strongly recommended, and are exhibited in the same way. Sugar is likewise highly spoken of as an antidote. In all cases a strong emetic should be first given.
_Obs._ Culinary and pharmaceutical vessels are very commonly made of copper, but too much caution cannot be exercised in their employment. Acid syrups, vegetable juices, aqueous extracts, soups, stews, &c., prepared in copper saucepans, or boilers, receive a metallic contamination proportional to the length of time they are exposed to the action of the metal. Such vessels are frequently tinned, for the purpose of protecting the copper from contact with their contents, but this film of tin is necessarily very thin, and soon becomes imperfect by constant use. When copper vessels are allowed to remain wet or dirty, or, more especially, greasy, a poisonous green rust forms upon the surface, somewhat similar to verdigris. If articles are prepared in them in this state, serious consequences may ensue. Cases of poisoning from this cause are frequently met with, and instances of vomiting following the use of such articles are almost of daily occurrence, without the reason being suspected. We have occasionally seen confections and extracts, prepared in copper pans, deposit a coating of that metal upon the knives used to stir them. The ashes of the inspissated juices of fresh vegetables, and especially the pulps of fruit, prepared in vessels of this metal, have exhibited the presence of copper on the application of chemical tests. Ketchup is frequently rendered poisonous in this way. The most wholesome material for culinary utensils is thin sheet iron, or tinned iron plate (TIN), which is very durable if kept clean and dry when not in use. Copper vessels of every kind should be cleaned out, immediately before use, even though they may not appear to require it, and on no account should they be employed for any fluids that are the least acidulous, or that may have to remain long in them.
The following enamel is recommended in Dingler's Polytechnic Journal for coating the inside of the copper vessels, used for cooking fruit or vegetables:--12 parts of white fluor-spar, 12 parts of unburnt gypsum, and 1 part of borax, are finely powdered, intimately mixed, and fused in a crucible. The fused mass is then poured out, and after cooling, is rubbed up to a paste. The copper vessel is then coated inside with this preparation, which is applied by means of a brush, and the vessel is placed in a moderately warm place, so that the coating may dry uniformly, when it is subjected to a gradually increasing heat, till at length the preparation fuses. On cooling, the vessel is found to be protected internally by a white opaque enamel, adhering very firmly to the copper, not chipping off by ordinary knocking and rubbing, and impervious to vegetable acids.
Copper may be cleaned by applying a small portion of the following paste, and rubbing it dry by a flannel or leather:--1 oz. oxalic acid, 6 oz. rotten stone, 1/2 oz. gum arabic, all in powder, 1 oz. of sweet oil, and sufficient water to make a paste.
=Copper, Neu'tral Acetate of.= Cu(C_{2}H_{3}O_{2})_{2}. _Syn._ NOR'MAL CUPRIC ACETATE, ACETATE OF COPPER, CRYS'TALLISED VER'DIGRIS. _Prep._ Dissolve common verdigris or cupric hydrate in hot acetic acid, so as to form a highly concentrated solution; filter and place in a cool situation to crystallise.
_Prop._ Beautiful dark, bluish-green prisms, which dissolve in 14 parts of cold and 5 parts of boiling water.
=Copper, Ba'sic Acetates of.= _Syn._ BA'SIC CU'PRIC ACETATES, SUB-AC'ETATES OF COPPER. Common verdigris is a mixture of several basic acetates which have a green or blue colour. One of these (SESQUIBASIC ACETATE) is obtained by digesting powdered verdigris in tepid water, filtering, and leaving the soluble part to spontaneous evaporation. It may also be obtained in a state of purity by adding liquor of ammonia in small portions to a boiling concentrated solution of the neutral acetate till the precipitate is just redissolved, and leaving the solution to cool. It forms a blue, crystalline mass, but little soluble in cold water. The green, insoluble residue of the verdigris, after treatment with tepid water, contains another acetate (TRIBASIC ACETATE); this may be formed by digesting neutral acetate of copper with the hydrated oxide. A third salt (DIBASIC ACETATE, BLUE VERDIGRIS) is prepared on a large scale in France by exposing copper to the air in contact with fermenting wine-lees.
=Copper, Ammo''nio-sul'phate of.= _Syn._ SULPHATE OF CUPRAMMONIUM. CU'PRO-SULPHATE OF AMMO''NIA; CU'PRI AMMO''NIO-SULPHAS, L.; CUIVRE AMMONIACAL, Fr.; KUPFER SALMIAK, Ger. _Prep._ Sulphate of copper, 1 oz.; sesquicarbonate of ammonium, 1-1/2 oz.; rub together until carbonic acid ceases to be evolved, then wrap it in bibulous paper, and dry it in the air.
_Pur._ Pulverulent; dark blue; at an intense heat it is changed into oxide of copper, at first sesquicarbonate of ammonia, and, afterwards, sulphate of ammonia, being thrown off. It is soluble in water to a splendid purple-blue solution, from which the salt is precipitated by alcohol in blue crystals. This solution has the peculiar property of dissolving CELLULOSE (cotton, paper, &c.). The cellulose may be precipitated from the solution in colourless flakes by the addition of acids.
_Uses., &c._ It is occasionally employed in _pyrotechny_. In _medicine_, it has been given in chorea, epilepsy, hysteria, &c., but is now principally used as an injection, as a wash for foul ulcers, used as a collyrium, in opacity of the cornea.--_Dose_, 1/4 gr., gradually increased to 5 gr., twice a day. Great care must be taken in drying, as it is apt not only to lose a large portion of its weight, but to become of an inferior colour. Both the ingredients should be separately reduced to powder before mixing them.
=Copper, Ar'senite of.= Cu(AsO_{2})_{2}. See GREEN PIGMENTS (Scheele's Green).
=Copper, Carbonate of.= CuCO_{3}. _Syn._ DIBA'SIC CARBONATE OF COPPER, DICARBONATE OF C.; CUPRI CARBONAS, L. _Prep._ Add carbonate of soda in excess to a solution of sulphate of copper, and warm the mixture till the pale-blue, flocculent precipitate becomes sandy and assumes a green tint. Used as a pigment. See GREEN PIGMENTS and VERDITER.
_Obs._ As prepared above, the carbonate contains 2 equivalents of water. The beautiful green mineral, MAL'ACHITE, has a similar composition, but contains only 1 equiv. of water. Another carbonate (TRIBASIC C., BLUE C.), occurs as a natural ore in large, transparent crystals, of the most intense blue; it has not yet been artificially imitated.
=Cuprous Chloride.= CuCl. _Syn._ DICHLORIDE OF COPPER, SUBCHLORIDE OF COPPER. _Prep._ By exposing the neutral chloride of copper to the action of heat.
_Prop._ White; fusible; slightly soluble in water; and decomposed by exposure to the air.
=Copper, Chloride of.= CuCl_{2}. _Syn._ NEUTRAL CHLORIDE OF COPPER. _Prep._ From copper scales or black oxide of copper dissolved in hydrochloric acid, and the solution evaporated and crystallised.
_Prop., &c._ Green, acicular crystals; deliquescent; soluble in alcohol, the flame of which it colours green. When gently heated it loses water, and assumes the form of a yellowish-brown powder (ANHYDROUS CUPRIC CHLORIDE, or CHLORIDE OF COPPER); at a high temperature it loses half its chlorine, and becomes converted into cuprous chloride.
=Cupric Iodide.= CuI_{2}. _Syn._ IODIDE OF COPPER, DINI'ODIDE OF COPPER; CU'PRI IODI'DUM. L. _Prep._ By adding iodide of potassium to a solution of sulphate of copper, and washing out with alcohol the free iodine from the precipitate formed. A greenish-white precipitate.
(Commercial.) To a solution of sulphate of copper, 1 part, and protosulphate of iron, 3 parts, add a solution of iodide of potassium, and wash and dry the precipitate. This is the preparation commonly known in trade by the name of 'iodide of copper.'
=Cupric Nitrate.= Cu(NO_{3})_{2}. _Syn._ NITRATE OF COPPER; CU'PRI NI'TRAS, L. _Prep._ By dissolving the copper in dilute nitric acid to saturation; evaporating to dryness; redissolving in distilled water; filtering, evaporating, and allowing to crystallise; or from black oxide of copper and nitric acid in the same manner.
_Prop., Uses, &c._ Deep-blue prismatic crystals, very soluble in water and deliquescent, soluble in alcohol. Generally used in medicine externally, in injections, or as a caustic, but sometimes given internally, dissolved in mucilaginous liquids.--_Dose_, 1/8 to 1/4 gr.
=Cuprous Oxide.= Cu_{2}O. _Syn._ RED OXIDE OF COPPER, DINOX'IDE, SUBOXIDE; CUPRI SUBOX'YDUM, L. _Prep._ Add grape sugar to a solution of sulphate or acetate of copper, then further add caustic potassa in excess; the blue solution heated to ebullition deposits the suboxide, which must then be collected, washed, and dried.
A solution of cane sugar, 27 parts, in water, 60 parts, is poured over hydrated oxide of copper (weighed in the compressed and still moist state), 9 parts; a solution of caustic potassa, 18 parts, in water, 60 parts, is then added, and the whole mass well agitated together at the ordinary temperature, and strained through linen. If the dark-blue filtrate is next heated (continually stirring), over a water bath, anhydrous cuprous oxide is disengaged, and the liquor becomes nearly colourless.
_Prop., Uses, &c._ A superb red powder, with a metallic lustre. It often occurs in beautiful transparent, ruby-red crystals, associated with other ores of copper, and can be obtained in this state by artificial means. It is used as a pigment and a bronze, and as a stain for glass and enamels, to which it gives a rich red colour. By heat it is converted into the black oxide. With ammonia it forms a colourless solution, which rapidly becomes blue from the action of the air.
=Cupric Oxide.= CuO. _Syn._ OX'IDE OF COPPER, BLACK OXIDE, PROTOXIDE; CU'PRI PROTOX'YDUM. _Prep._ By heating the nitrate or carbonate of copper to redness. When it ceases to lose weight the conversion is completed, and the oxide appears as a heavy, black powder.
By heating in the air the hydrated oxide thrown down from solutions of copper by pure potassa.
By adding caustic potassa, in excess, to a solution of a cupric salt, and heating the whole to a boiling-point; the precipitate is then collected, washed, and dried. A heavy, dark-brown powder.
_Uses, &c._ Protoxide of copper is unchanged by heat unless combustible matter is present, when it readily parts with its oxygen; hence its general use in ORGANIC ANALYSIS as a source of that element. It communicates a beautiful green colour to glass and enamels. With the acids it produces the ordinary salts of copper.
=Cupric Sulphate.= CuSO_{4}.5Aq. _Syn._ SULPHATE OF COPPER, BLUE COP'PERAS, B. VIT'RIOL; CU'PRI SUL'PHAS, L.; SULFATE DE CUIVRE, Fr.; KUPFER VITRIOL, Ger.; NEELA TOOTIA, Hind. _Prep._ (Commercial.) The sulphate of copper of commerce is obtained by the oxidation of native sulphide of copper (COPPER PYRITES); by the joint action of air, heat, and moisture, the copper is converted into an oxide, and the sulphur into sulphuric acid. The resulting salt is washed out, and the solution evaporated and crystallised. The water found in and issuing from copper mines often furnishes such a solution ready to the hands of the manufacturers. A large quantity of sulphate of copper is also obtained as a secondary product in the refining of silver, and is occasionally prepared by dissolving in sulphuric acid an oxychloride of copper, made for the purpose by exposing sheets of copper to the joint action of air and hydrochloric acid.
(Pure.) By the direct solution of the metal, or preferably, of its oxide or carbonate in sulphuric acid, or by purifying the commercial salt by recrystallisation, &c.
_Prop., Uses, &c._ Fine blue crystals, slightly efflorescent, having an intensely styptic and metallic taste. By heat the blue salt loses its water of crystallisation, and becomes a white, anhydrous powder. It dissolves in 4 parts of water at 60° Fahr., and in 2 parts at 212°; is insoluble in alcohol and ether; and is decomposed at an intense heat into protoxide of copper, sulphurous acid, and oxygen. It has been used to prevent the dry rot in timber and in dyeing. It is largely employed as a source of metallic copper in the ELECTROTYPE. Grain is steeped in a weak solution of it by the farmer, to prevent the 'smut,' As a medicine, it is employed chiefly as a styptic (in solution) and caustic (in substance) to destroy 'proud flesh,' and, less frequently, as an astringent or tonic (from 1/4 gr. to 2 gr.), and an emetic (3 or 4 gr. to 10 or 12 gr). It is exceedingly poisonous.
=COP'PERAS.= This is a generic name for the CRUDE METALLIC SULPHATES. When used without a qualifying adjective, it generally means sulphate of iron.
=Copperas, Blue.= Crude sulphate of copper. See COPPER (_above_).
=Copperas, Calcined'.= From green copperas, heated in an unglazed earthen pot until it becomes white and dry. Used as an astringent and 'drier,' and in making ink and dyeing.
=Copperas, Green.= _Syn._ COPPERAS. Crude sulphate of iron. See IRON.
=Copperas, White.= Crude sulphate of zinc. See ZINC.
=COP'PERING.= Iron may be covered with a thin film of copper by merely immersing it (previously scoured clean) in an acidulated solution of sulphate of copper, after which it must be rinsed in clean water. This film soon rubs off, but still it lasts long enough to deceive the travelling tinker's customers, who imagine that their copper kettles are properly repaired. Metals may be conveniently coated with compact copper to any desired thickness by means of voltaic electricity. See ELECTROTYPE.
=COP'ROLITE.= _Syn._ DUNG'STONE, FOSSIL MANURE. This mineral is the petrified dung of carnivorous reptiles. (Buckland.) Coprolites are found in all the secondary and tertiary strata. They contain a considerable proportion of phosphate of lime, for which reason they are largely employed in the manufacture of artificial manures. They form the bases of Lawes' SUPERPHOSPHATE OF COPROLITE MANURE. The nodules, after being washed, are ground to powder in a mill, and mixed with an equal weight of oil of vitriol.