(2) Franklinite (RO.M 2 O 3 , where R stands for Zn, Fe, Μη; M for Fe, Mn). The zinc averages about 10 per cent. It crystallizes in regular octahedra, with rounded-off edges and angles. Sp. gr. 5∙1. Colour, black; streak, reddish-brown. Lustre, sub-metallic. This and the preceding occur in association with each other and other things in New Jersey, U.S.

(3) Calamine (ZnCO 3 ). The pure mineral (zinc spar) forms well-defined, though small, rhombohedra. The ordinary ore is massive, and is contaminated, often largely, with clay, silica, oxide of iron, and the like. Sp. gr. 4 to 4∙5. Sometimes colourless, but as a rule light grey, yellow, or buff-coloured. Lustre, vitreous. It is found in association with silicates of zinc, zinc-blende, and lead ores, chiefly in limestone and dolomitic strata, at the Kelmisberg or Vieille Montagne in Belgium, in Derbyshire and Northumberland, and in Silesia; but these last deposits are well nigh exhausted. Irregular deposits occur near Santander and Cartagena in Spain, and in Sardinia. At Wiesloch in Baden a yellow variety is found, which contains as much as 3 per cent. of cadmium. Smaller percentages of cadmium are met with in many other zinc ores.

(4) Electric Calamine, the German Kieselzinkerz (ZnOSiO 2 + H 2 O), is also called hemimorphite on account of the marked hemimorphism in its (ortho-rhombic) crystals. Sp. gr. 3∙35 to 3∙5. Sometimes colourless, but more frequently grey, yellow, red, green, brown, blue,—always, however, light-coloured. Lustre, vitreous. The crystals, when heated, exhibit electric polarity; hence the name. As a rule they are small and united into cuneiform, spheroidal, or kidney-shaped masses; there are also granular, dense, and earthy varieties. It occurs with willemite and calamine at the Altenberg near Aix-la-Chapelle, with blende and lead ore at Raibel and Bleiberg in Carinthia, near Iserlohn in Westphalia, at Matlock in Derbyshire, near Tarnowitz in Silesia, at Olbucs, Rezbanya in Hungary, and Nertchinsk in Siberia. American sources are at Phoenixville and Friedenswille in Pennsylvania and in the Austin mine in Virginia.

(5) Willemite, anhydrous ZnOSiO 2 , occurs in New Jersey and elsewhere; it is a comparatively rare ore.

(6) Zinc-Blende, or shortly Blende (ZnS).—The five ores mentioned above, as indeed all oxidized zinc ores, having become scarce, most of the zinc which now occurs in commerce is derived from zinc-blende. This ore crystallizes in combinations of the two tetrahedra and other forms of the regular system. Sp. gr. 3∙9 to 4∙2. Colour, green, yellow, red, but mostly brown or black. Colourless crystals are scarce. Lustre, fatty or diamond-like. The ordinary ore forms crypto-crystalline or fibrous or granular masses, which sometimes present the form of kidneys, consisting of concentric layers. The finest crystals are found in Franklin, New Jersey, which are colourless and consist of pure ZnS, and in the Penas de Europa, Asturias (Spain), in which liquid enclosures are often met with. The darker varieties, which always include more or less of foreign sulphides, are found in a great number of places. In Cornwall, Wales, Alston Moor in Cumberland, Teesdale in Yorkshire, Derbyshire, and the Isle of Man dark-coloured blende is found in the lead-mining districts with galena, quartz, and limestone. In Belgium and on the Rhine massive blende occurs with iron pyrites and galena; this ore requires a great deal of sorting to become fit for smelting. In Sweden blende is frequently found: at Ammeberg on Lake Wetter a vast deposit occurs in the gneiss. To English miners blende is known as “black Jack,” to the South Americans as “chumbe.” The principal American deposits are in Missouri.

Metallurgy.— Oxide of zinc, like most heavy metallic oxides, is easily reduced to the metallic state by heating it to redness with charcoal; but, as zinc has the exceptional property of being readily volatile at the temperature of its reduction, the operation must be carried out in some kind of retort, and the zinc be recovered as a distillate. To pure red zinc ore the operation of distilling with charcoal might be applied quite directly; and the same might be done with pure calamine of any kind, because the carbonic acid of carbonate of zinc goes off below redness and the silica of silicate of zinc only retards, but does not prevent, the reducing action of the charcoal. Zinc-blende, however, being sulphide of zinc, is not directly reducible by charcoal; but it is easy to convert it into oxide by roasting: the sulphur goes off as sulphurous acid, whilst the zinc remains in the (infusible) form of oxide, ZnO. In practice, however, we never have to deal with pure zinc minerals, but with complex mixtures, which must first of all be subjected to mechanical operations, to remove at least part of the gangue, and if possible also of the heavy metallic impurities (see Metallurgy, vol. xvi. p. 59 sq.). And, supposing this to be done, the ore, even if it is not blende, must be roasted, in order to remove all volatile components as completely as possible, because these, if allowed to remain, would carry away a large proportion of the zinc vapour during the distillation. If the zinc is present as blende, this operation offers considerable difficulties, because in the roasting process the sulphide of zinc passes in the first instance into sulphate, which demands a high temperature for its conversion into oxide. Another point to be considered in this connexion is that the masses of sulphurous acid evolved, being destructive of vegetable life, are an intolerable nuisance to the neighbourhood in which the operations take place.

Hasenclever and Helbig have constructed a furnace by which some two-thirds of the sulphurous acid can be conducted into chambers and condensed into the useful form of oil of vitriol. Figs. 1, 2, and 3 show how the furnace is constructed. k is a Siemens gas furnace, n being the orifice for the introduction of the fuel; the gases go out at m, where they mix with air; the flame travels between the sole g and the bottom of the muffle c , and then goes along the top of the muffle to the flue q; it passes below the slanting canal bb and keeps it at a temperature above the fusing-point of antimony (432° C.). The ore is introduced through the funnel a ; it slides down the slanting canal bb; the partition walls d, d, which follow each other at distances of half a metre, compel it to spread out evenly into a thin layer. The partition walls, as shown by fig. 3, are arranged so that the gases coming from the muffle must travel along an undulating line and lick up as much as possible of the sulphur of the ore. From the last compartment e the gaseous product goes first to a cooling chamber, and thence to the vitriol chamber. The hollow cylinder f, which is cooled internally by air while made to revolve, conveys the ore in instalments from the bottom end of the canal to the muffle. At intervals of two hours it is spread evenly on the bottom of the muffle, and at last it is drawn out through o and transferred to the sole g, to be finally roasted (“todtgerostet”) there. The apparatus works very satisfactorily even with ores poor in sulphur. An ore containing 20 per cent. of sulphur contained at the end f of the inclined canal 10 per cent., at the end o of the muffle 6∙4 per cent., and at last, when “todtgerostet,” only 1∙2. About one-third of the sulphur is lost, i.e., goes out through the chimney, as SO 2 ∙

The distillation process in former times, especially in England, used to be carried out “per descensum.” The bottom of a crucible is perforated by a pipe which projects into the crucible to about two-thirds of its height. The powdery mixture of ore and charcoal is put into the crucible around the pipe, the crucible closed by a luted-on lid, and placed in a furnace constructed so as to permit of the lower end of the pipe projecting into the ash-pit. The zinc vapour produced descends through the pipe and condenses into liquid zinc, which is collected in a ladle held under the outlet end of the pipe. For manufacturing purposes a furnace similar to that used for the making of glass was employed to heat a circulai· row of crucibles standing on a shelf along the wall of the furnace. This system, however, has long been abandoned; at present one or other of the following methods is used as a rule.

In the Belgian process the reduction and distillation are carried out in cylindrical retorts of fire-clay, about a metre long and 0∙15 metre wide inside. Some forty-six or more retorts, arranged in eight parallel horizontal rows, are heated in one furnace. The furnaces are square and open in front, to allow the outlet ends of the retorts to project; they are grouped together by fours; and their several chimneys are within the same enclosure. Each retort is provided with two adapters, namely, a conical pipe of fire-clay, about 0∙4 metre long, which fits into the retort end, and a conical tube of black sheet iron, which fits over the end of the fire-clay pipe, and which at its outlet end is only 2 centimetres wide. To start a new furnace, the front side is closed provisionally by a brick wall, a fire lighted inside, and the temperature raised very gradually to a white heat. After four days’ heating the provisional front wall is removed piecemeal, and the retorts, after having been heated to redness, are inserted in corresponding sets. The charge of the retorts consists of a mixture of 1100 lb of roasted calamine and 550 lb of dry powdered coal per furnace. A newly-started furnace, however, is used for a time with smaller charges. Supposing the last of these preliminary distillations to have been completed, the residues left in the retorts are removed and the retorts, as they lie in the hot furnace, are charged by means of semi-cylindrical shovels, and their adapters put on. The charging operation being completed, the temperature is raised, and as a consequence an evolution of carbonic oxide soon begins, and becomes visible by the gas bursting out into the characteristic blue flame. After a time the flame becomes dazzling white, showing that zinc vapour is beginning to escape. The iron adapters are now slipped on without delay, and left on for two hours, when, as a matter of experience, a considerable amount of zinc has gone out of the retort, the greater part into the fire-clay adapter, the rest into the iron cone. The former contains a mixture of semi-solid and molten metal, which is raked out into iron ladles and cast into plates of 66 to 77 lb weight, to be sold as “spelter.” The contents of the iron recipient consist of a powdery mixture of oxide and metal, which is added to the next charge, except what is put aside to be sold as “zinc dust.” This dust may amount to 10 per cent. of the total production. As soon as the adapters have been cleared of their contents, they are replaced, and again left to themselves for two hours, to be once more emptied and replaced, &c. The complete exhaustion of the charge of a furnace takes about 11 hours.

In the Silesian process the distillation is conducted in specially constructed muffles, which are arranged in two parallel rows within a low-vaulted furnace, pretty much like the pots in a glass furnace. As a rule every furnace accommodates ten muffles. Through an orifice in the outlet pipe (which during the distillation is closed by a loose plug) a hot iron rod can be introduced from time to time to clear the canal of any solid zinc that may threaten to obstruct it. As soon as the outlet pipe has become sufficiently hot the zinc flows through it and collects in conveniently placed receptacles. About 6 or 8 hours after starting the distillation is in full swing, and in 24 hours it is completed. A fresh charge is then put in at once, the muffles being cleared only after three successive distillations. The distillate consists of a conglomerate of drops (“drop zinc”). It is fused up in iron basins lined with clay, and cast out into the customary form of cakes. In some modern works the muffles are heated by means of Siemens’s regenerative gas furnace, by which a more uniform heat can be secured and maintained at a less cost.

Of the several metallic impurities in zinc ores iron is at once the most common and the least objectionable, because it is absolutely non-volatile at the temperature of a zinc retort; whenever commercial zinc contains iron, this comes from its having been re-fused in iron vessels after its distillation. Lead, though hardly volatile by itself at a red heat, if present in the ore, is, so to say, carried over by the zinc vapour and passes at least partly into the distillate. Cadmium and arsenic being more volatile than zinc itself, if present, accumulate in the first fractions of the distillate, but may pervade it in traces to the end. Zinc made from oxidized ores is usually free from arsenic; that derived from blende is almost sure to contain it. This in practice is equivalent to saying that, while in former times it was easy, it is now very difficult, to obtain in commerce zinc free from arsenic. Traces of arsenic do not, however, interfere with any of the technical applications of the metal. As for cadmium, it is not (metallurgically speaking) an impurity at all, but, like silver in lead, a rather desirable admixture which it may be worth while to extract.

No reliable method is known by which commercial zinc could be purified so as to render it fit for all the purposes of the analyst; the only way to obtain really pure zinc is to prepare it from pure oxide by distillation with charcoal in a non-metallic retort.

Properties of Pure Zinc.— Zinc, a bluish-white metal, fuses at 415° C. and under ordinary atmospheric pressure boils at 1040° C. (Deville and Troost). The molten metal on cooling deposits crystals, and at last freezes into a compact crystalline solid, which may be brittle or ductile according to circumstances. According to Bolley, if zinc be cast into a mould at a red heat, the ingot produced is laminar and brittle; if cast at just the fusing-point, it is granular and sufficiently ductile to be rolled into sheet at the ordinary temperature. According to some authorities, pure zinc always yields ductile ingots. A clue to the explanation of these anomalous facts is afforded by certain observations of Gustav Rose and others, from which it appears that zinc is dimorphous and may or may not crystallize in the regular system. Supposing a mass of molten zinc to freeze into, say, cubes, the ingot will be ductile; an ingot of, say, rhombohedra, on the other hand, is almost bound to be brittle, because the crystals are orientated in a lawless fashion, and, as they cannot be expected to contract at the same rate in all directions, we must be prepared for a brittle ingot. Commercial “spelter” always breaks under the hammer; but at 100° to 150° C. it is susceptible of being rolled out into even a very thin sheet. Such a sheet, if once produced, remains flexible when cold. At about 200° C., again, the metal becomes so brittle that it can be pounded in a mortar. The specific gravity of zinc cannot be expected to be perfectly constant; according to Karsten, that of pure ingot is 6∙915, and rises to 7Ί91 after rolling. The coefficient of linear expansion is 0∙002,905 for 100° from 0° upwards (Fizeau). The specific heat is 0∙093,93 (Schüller and Wartha). Compact zinc is bluish white; it does not tarnish much in the air. It is pretty soft, and clogs the file. If zinc be heated up to near its boiling-point, it catches fire and burns with a brilliant light into its powdery white oxide, which forms a reek in the air liana philosophica). Boiling water attacks it appreciably, but no more, with evolution of hydrogen and formation of hydroxide, Zn(OH) 2 . A rod of perfectly pure zinc, when immersed in dilute sulphuric acid, is so very slowly attacked that there is no visible evolution of gas; but, if a piece of platinum or other less basilous metal is brought into contact with the zinc, it dissolves readily, with evolution of hydrogen and formation of sulphate. The ordinary impure metal dissolves at once, the more readily the less pure it is. Cold dilute nitric acid dissolves zinc as nitrate, with evolution of nitrous oxide, N 2 O, and formation of nitrate of ammonia. At higher temperatures, or with stronger acid, nitric oxide, NO, is produced besides or instead of nitrous.

Oxide of Zinc, ZnO.—There is only this one oxide. It is prepared chiefly in two ways,—(1) by burning the metal, a method now being carried out industrially, the zinc vapour being sometimes produced extempore from a mixture of roasted ore and carbon, and (2) by heating the basic carbonate (see below). It is an infusible solid, which is intensely yellow at a red heat, but on cooling becomes white. This at least is true of the oxide produced from the metal by combustion; that produced from the carbonate, if once made yellow at a red heat, retains a yellow shade permanently. Oxide of zinc is insoluble in water, and does not combine directly with it; it dissolves readily in all aqueous acids, with formation of “zinc salts.” It also dissolves in aqueous caustic alkalies, including ammonia, forming “zincates” (e.g., ZnO.KHO). Oxide of zinc is used in the arts as a white pigment; it has not by any means the covering power of white lead, but offers the advantage of being non-poisonous and of not becoming discoloured in sulphuretted hydrogen. It is used also in medicine, chiefly externally.

The hydrate, Zn(OH) 2 , is prepared by precipitating a solution of any zinc salt with caustic potash. The alkali must be free from carbonate and an excess of it must be avoided, otherwise the hydrate re-dissolves. It is a white powder, and is insoluble in water. To acids and to alkalies it behaves like the oxide, but dissolves more readily.

The basic carbonate, ZnCO 3 .x Zn(OH) 2 , where x is variable, is prepared by precipitation of a solution of the sulphate or chloride with carbonate of soda. To obtain a product free of Cl or SO 4 , there must be an excess of alkali and the zinc salt must be poured into the hot solution of the carbonate. The precipitate, eveu after exhaustive washing with hot water, still contains a trace of alkali; but from the oxide, prepared from it by ignition, the alkali can be washed away. The basic carbonate is, like the oxide, used as a pigment. Normal carbonate...

The old cornets were of two kinds,—the straight and the curved. The straight (Germ. gerade Zincken, stille Zincken; Ital. cornetti diritti, cornetti muti) were usually made with the mouthpiece (a cupped mouthpiece analogous to that of the trumpet) forming part of the tube. The curved (Germ. krumme Zincken ; Ital. cornetti curvi) are formed of two pieces of wood of different lengths, each having half the channel in which the column of air is to vibrate hollowed out, the diameter increasing from the mouthpiece towards the lower end. The two pieces of wood, when thus prepared, are joined together with glue; they are then finished off so as to form a pipe with eight sides, and are finally covered with leather. The mouthpieces are made of wood, horn, or ivory, and are fixed by a tenon to the upper extremity of the pipe. The primitive instrument was an animal’s horn. Pipes of such small length give only, besides the first or fundamental, the second and sometimes the third note of the harmonic series. Thus, a pipe that has for its fundamental note A will, if the pressure of the lips be steadily increased, give the octave A and the twelfth E. To connect diatonically the first and second, the length of the pipe was progressively shortened, by making holes in its substance for the fingers to cover. The opening of these holes successively furnished the instrumentalist with the different intervals of the scale, six holes sufficing for this purpose: The fundamental was thus connected with its octave by all the degrees of a diatonic scale which could become chromatic by the help of cross fingerings and greater or less pressure of the lips within the mouthpiece. The fingering was completed by a seventh hole, which had for its object the production of the octave without the necessity of closing all the holes in order to produce the second note of the harmonic series. The first complete octave, thus obtained by a succession of fundamental notes, is easily octaved by a stronger pressure of the lips against the mouthpiece, and thus the ordinary limits of the compass of a zincke or cornet extend to a fifteenth. Whether straight or curved, it is pierced laterally with seven holes, six through the front and the seventh, that nearest to the mouthpiece, through the back. The first three holes were usually covered with the third, second, and first fingers of the right hand, the next four with the third, second, and first fingers and the thumb of the left hand. But some instrumentalists inverted the position of the hands. Virdung shows a kind of zincke made of an animal’s horn with only four holes, three at the back of the pipe and one in front. Such an instrument as this had naturally a very limited compass, since with the help of these four holes only the intermediate notes between the second and third proper tones of the harmonic scale could be produced, the lower octave comprised between the first and second remaining incomplete. At the beginning of the 17th century Praetorius represents the zincken as a complete family arranged thus :—(1) the little zincke, of which the lowest note was that showm in (i.); (2) the ordinary zincke, with lowest note (ii.); and (3) the cornon, como torto, or great zincke, with lowest note (iii.). In France the family was composed of the following instruments:—(1) the dessus, with lowest note (a ); (2) the haute-contre, with lowest note (b ); (3) the taille, with lowest note (c); and (4) the basse, with lowest note (d ). Numbers (2), (3), and (4) in this last series were sometimes furnished with an open key, which, when the closed tube was lengthened, augmented the compass downwards by a note.

During the Middle Ages these instruments were in such favour that an important part was given to them in all instrumental combinations. In Germany, in the 18th century, they were used with trombones in the churches to accompany the chorales. There are examples of this employment in the sacred cantatas of J. S. Bach. Monteverde made use of them in his opera Orfeo in 1608, as did Gluck in the opening chorus of his Orfeo, played at Vienna in 1762. The great vogue of the zincke is not to be accounted for by its musical qualities; for it has a hard, hoarse, piercing sound, and it failed utterly in truth of intonation; and these natural defects could only be modified with great difficulty. It is now hard to understand Mersenne’s eulogium of the dessus, then more employed than the other cornets, “because it was used in vocal concerts and to make the treble with the organ, which is ravishing when one knows how to play it to perfection, like the Sieur Quiclet,” and, farther on, “as to the property of its tone, it resembles the brilliancy of a sunbeam piercing the darkness, when it is heard among the voices in churches, cathedrals, or chapels.”

The serpent is another instrument of the cornet family, though not usually classed with it. Its construction and its acoustic principle are the same as those of the old cornet. It is, properly speaking, an enlarged cornet with one hole less, that which is stopped with the thumb. The mouthpiece is fixed to the instrument by means of a long brass crook. A detailed account of the serpent and its congeners is given under Ophicleide (vol. xvii. p. 778). The zincke or cornet has now entirely disappeared, and the rare specimens still met with are eagerly sought by collectors. The serpent has lasted longest, and even within the last twenty years has been used in many churches in the south of France.

Cornet, Cornet À Pistons.

At present the names of cornet, cornet à pistons, and cornopean are given to an instrument that has no analogy whatever to the mediaeval cornet. It is a transformation of the old post-horn, with a shorter tube than that of the trumpet, and improved to such a degree that its quality of tone is intermediate between the brightness of the trumpet and the softness of the flügel-horn or bugle with pistons. The extent of the modern cornet without pistons is comprised within the second and eighth of the harmonic scale The seventh, being too flat, owing to a well-known acoustic phenomenon, is rarely used. The cornet à pistons of the highest pitch is in B♭,, and is used for a trumpet in that key. The notes written therefore sound a major second lower than the notation. It is furnished with three pistons, which lower the principal tube by a whole tone (1st piston), a half tone (2d piston), and a tone and a half (3d piston) respectively. It has already been explained under Trombone how the different pistons are combined to produce the entire chromatic compass of the instrument from the lowest limit

At first the cornet à pistons was supplied with a great many crooks. There were crooks for A, A♭, G, F, E, E♭, and D; but it is easy to understand that, if the additional tubes put in communication with the principal column of air by means of the pistons are adjusted for the key of Bb, the same additional tubes are too short to fulfil the same office for an instrument lowered to the extent of a minor sixth, as it would be for the key of D. Hence nearly all these crooks have disappeared, only those for B♭, A, and A♭ being retained. The invention of the modern comet, or more exactly the application of pistons to the post-horn, is German, and dates from the first quarter of the 19th century, almost immediately after the invention of pistons by Stölzel and Blümel. It was introduced into Great Britain and France about 1830. There were at first only two pistons,—that of the whole tone and that of the half tone,— from which there naturally resulted gaps in the chromatic scale of the instrument. The history of the cornet is that of the improvement brought about by pistons apart from their successive transformations, and it has remained to the present time what it was when first invented. The great favour the cornet meets with is due to the facility with which it speaks, to the little fatigue it causes, and to the simplicity of its mechanism. We may, however, regret, from the point of view of art, that its success has been so great, and that it has ended by usurping in brass bands the place of the bugles, the quality of their tone being infinitely preferable as a foundation for an ensemble composed exclusively of brass instruments. Even the symphonic orchestra has not been secure from its intrusion. In fact, the cornet is taking the place of the trumpet nearly everywhere, and, if care is not taken, the latter will in a few years have completely disappeared, to the great detriment of orchestral tone colour; for the quality of tone of the cornet can never be an adequate substitute for the brilliant and majestic sonorousness so characteristic of the trumpet. (V. Μ.)