Zinc, Or Spelter (symbol, Zn; chemical equivalent, 65; specific gravity, 7.03 to 7.2), a highly lustrous white metal, with a bluish gray tint. It crystallizes in forms not perfectly recognized - according to Noggerath and Plattner in hexagonal prisms, and according to G. Rose in monometric forms also, hence probably dimorphous. On fresh fractures it presents a beautiful foliated crystalline structure. It is comparatively soft, but harder than tin, and is brittle or malleable and ductile, according to temperature, viz.: at ordinary temperatures brittle, parting along cleavage faces; between 100 and 1500 C. (212° and 302° F.) malleable and ductile, so that it can be drawn into wiro or beaten or rolled into plates; at 200° C. (392° F.) so brittle that it may be pulverized in a mortar having this temperature. It is fusible at 412° C. (773° F.), and volatile at high red heat. It expands rapidly when heated (1/333 of its length in passing from 0° to 100° C), and contracts when cooled. The boiling point, according to Deville, is about 1040° C. (1904° F.); according to Becquerel, 891° C. (1636° F.). The temperature of melting also affects the brittleness. Cast at a high heat, zinc is brittle; but cast at the lowest practicable temperature, it is malleable.

The cause of this appears to lie in the connection between crystalline structure and brittleness. In preparing zinc to be rolled, it is usually melted in large kettles, and before casting in warmed moulds pieces of solid zinc are thrown into the bath to reduce its temperature. The process of rolling hardens it, but it may be annealed at low heat. It is not highly tenacious; zinc wire 1/12 in. in diameter sustains 25 lbs., or about two tons per square inch of section. The vapor of zinc burns in the air with a brilliant bluish white flame to flocculent white oxide (zinc white, the nihil album, fiores zinci, or lana philosophica of the alchemists, and the pompholyx of the ancient Roman metallurgists), which is not easily fusible or volatile, but is mechanically carried by the draft attending combustion, so that its deposition in settling chambers as an almost impalpable precipitate has a superficial resemblance to sublimation and condensation. If zinc is melted and brought to glowing heat under access of air, it burns to oxide, which may be skimmed from the metallic bath. Fine turnings of zinc will burn to oxide if lighted- with a match.

Exposed to a moist atmosphere, the metal soon loses its lustre, acquiring a thin gray film (often called oxide, and sometimes suboxide, but more correctly a basic carbonate), which, closely adhering to it, protects it from further change. The usefulness of this property is evident. Pettenkofer found that upon a sheet of zinc which had been exposed as part of a roof for 27 years, the oxidizing action had penetrated but 0.01 millimetre. In the presence of air, zinc decomposes water, producing zincic oxide and liberating hydrogen. In this way hydrogen is made for laboratories, dilute sulphuric or hydrochloric acid being used instead of pure water, and zincic sulphate or chloride being formed, which is removed by solution from the surface of the metal, greatly assisting the rapidity and uniformity of the liberation of hydrogen. Boiling solutions of potash are also decomposed by zinc in a similar manner, the resulting zincic oxide being dissolved. Zinc is the most electro-positive of the metals, whence its use in galvanic batteries, etc.; and the presence of electro-negative metals, producing galvanic action, facilitates the reactions above described. Indeed, chemically pure zinc is with difficulty acted upon by acids in a glass vessel.

The ordinary zinc of commerce is never perfectly pure, but contains various ingredients derived from its ores or from the apparatus of reduction. The purest commercial zinc is that of Pennsylvania and New Jersey, as appears from the following analyses given by Kerl:

Nos. 1 and 2, Upper Silesia; 3, Bleiberg; 4, Dombrowa; 5, Carniola; 6, Austria; 7, La Salle, 111.; 8, Bethlehem, Lehigh co., Pa.; 9, Engis (from calamine); 10, Engis (from blende). The amount of arsenic in European zincs is said to range from 0'0005 per cent, in the best Belgian to 0.19 per cent, in the worst French. The zinc of Freiberg in Saxony contains about 0.04 per cent, of iridium; that of Johannisthal in Carinthia, 0.2 to 0.5 per cent, of sulphide of lead; that of New Jersey is doubtfully reported to contain traces of copper and tin. Manganese, antimony, and even cobalt and nickel, are also named as occurring in traces in commercial zinc. The Silesian metal derives its high- percentage of iron (shown in the above table) from the kettles in which it is melted. Cadmium frequently accompanies it in its ores, as manganese does iron, replacing it to some extent in the chemical formulas of the minerals, or forming combinations isomorphous with those of zinc. - As will be inferred from the foregoing, zinc readily forms alloys, the most important of which are those with copper, or copper and nickel. Ordinary brass contains about 71.5 parts copper to 28.5 zinc; pinchbeck, 84.5 copper Co 15.5 zinc.

The term tombac, employed in German for pinchbeck, appears to be used at present by English writers in a different sense. According to Brande, tombac is brass with an excess of zinc; and later English authors apply the term to white copper, an alloy of copper and arsenic. There are numerous other alloys of zinc and copper, or zinc, copper, and tin, composing a great variety of oroides or imitations of gold, bronze powders, button metals, etc. German silver or argentan (originally imported from China under the name of paclcfong or white copper) is an alloy of copper, zinc, and nickel, much employed as a substitute for silver in utensils, and especially as a basis for the best silver plate (electro-plate). The general rule is said to be that copper and zinc in this alloy should bear the proportion of 8:3, and that the nickel should be not less than one fourth nor more than three fourths of the amount of copper. But Aubelen says that copper 3, zinc 1, and nickel 1 gives the best alloy for working, and also most nearly resembling silver; and many analyses of good English ware approach this composition.

The alloy of zinc and silver plays an important part in the processes of Parkes, Cordurie, Flach, and others, for the desilverization of argentiferous lead. (See Lead, and Silver.) Apart from its alloys, zinc is used for ornamental castings (statuettes, &c), which are to be painted, copper-plated, or bronzed. For this purpose it is adapted by its cheapness, fusibility, and property of filling the mould completely without shrinkage, giving sharply defined castings. It is also employed as sheet zinc in roofing, cornices, signs, vessels, etc.; for coating iron (see Galvanized Iron); for sheathing ships; as fuel, so to speak, in the galvanic battery; and in the preparation of hydrogen by the decomposition of water. The Dobereiner lamp, once common, but now superseded by friction matches, is a small hydrogen generator, consisting of a bell glass in which is suspended a piece of zinc, and which is placed in a jar containing very dilute sulphuric acid. The action of the acid and water upon the zinc liberates hydrogen, which, collecting in the upper part of the bell glass, drives the liquid down and out into the surrounding jar; so that when a certain quantity of the gas has accumulated the zinc is no longer in contact with the liquid, and the process ceases until, the hydrogen being drawn off, the liquid rises again under the bell, and again attacks the zinc.

The hydrogen, when a light is required, is allowed to escape through a small cock at the top, and to impinge upon a ball of platinum sponge, which, condensing the gas in its pores, grows white hot, and sets the hydrogen jet on fire. For the production of pure hydrogen the zinc must be free from arsenic, traces of which are common in the commercial article. This is particularly important in Marsh's test for arsenic. - The most important compounds of zinc are the oxide, carbonate, chloride, sulphate, and acetate. The oxide, flores zinci, ZnO (80 parts of zinc to 20 of oxygen), a soft white or faintly yellow, tasteless, and inodorous powder, turning lemon-yel* low when heated, and recovering its whiteness on cooling, has been used medicinally as a tonic and anti-spasmodic, in epilepsy, whooping cough, chorea, and various spasmodic affections, and as an exsiccant, externally applied in powder or in ointment to excoriations, slight ulcerations, etc. In the manufacture of spelter and the melting of brass, a portion of the zinc is volatilized and oxidized, the oxide settling on the walls of the furnace in a white or gray mass.

The former is called by pharmacists nihil album, the latter tutia Alexandrina, though under both these names substances are now sometimes offered which consist of gypsum or other earthy minerals, without a trace of zincic oxide. The metallurgical name is furnace calamine or cadmia. The carbonate is best precipitated by pouring a hot, pure solution of the sulphate into one of sodic carbonate. It is used medicinally in fine powder, dusted externally upon excoriations, etc., as a mild astringent and exsiecant. The native carbonate, or smithsonite, formerly called calamine, one of the principal ores, is considered below. Zincic chloride, or butter of zinc, ZnCl2, is prepared by heating zinc in chlorine gas, or by dissolving it in muriatic acid. In the latter case hydrogen escapes, and the chloride is left in the solution, which upon heating gives off steam, until at 250° C. (482° F.) the anhydrous salt remains. But this is still fluid, and may be heated up to 371° 0. (700° F.) without great volatilization. Hence this substance is used in the laboratory as a heating bath for high temperatures. Pure zincic chloride is a white, semi-transparent, waxy substance, fusible, deliquescent, corrosive to the skin, and possessing even in weak solution a burning, nauseous, saline taste.

It is employed internally as an alterative and antispasmodic (in over doses, a corrosive poison, for which the alkaline carbonates are antidotes), and externally as a caustic, by some considered superior to argentic nitrate. In concentrated solution it is an antiseptic and preservative of vegetable fibre against decay. (See Disinfectants, and Preservation of Wood.) It absorbs ammonia freely, and unites with alkaline chlorides to form double chlorides, and with ZnO to form oxychlorides. A concentrated solution of zincic ammonic chloride is used to cleaji the surfaces of metals before soldering, by removing the metallic oxides. A solution of zincic chloride containing iodine and potassic iodide is recommended in microscopy for giving to the cellulose of vegetable objects (for instance, to cotton) a violet or blue tint, without injury to their structure. An artificial filling for teeth ("bone filling ") is made by intimately mixing one part of very fine glass powder with three parts of pulverized zincic oxide; then, in a different vessel, preparing a concentrated solution of zincic chloride, to which about 2 per cent, of hot concentrated borax solution is added. With the compound solution, the powder is moistened to a paste just before using.

In a few minutes (the borax serving merely to retard the reaction somewhat) the mass " sets," by reason of the formation of oxy chloride, which, together with the glass powder, presents a degree of hardness at least equal to that of marble. Zincic sulphate, or white vitriol, occurs in mine waters or as efflorescence in mines, where the sulphide (zinc blende) is among the ores. It is produced for use in the arts by calcining zinc blende in heaps, leaching, evaporating, crystallizing, etc. The commercial salt may contain sulphates of iron, copper, manganese, magnesia, or lime. Large quantities of the solution of zincic sulphate are produced in telegraph and other galvanic batteries in which dilute sulphuric acid acts upon metallic zinc. Its crystals are rhombic prisms, colorless, transparent, very soluble in water, and slightly efflorescent in the air. If prepared by slow evaporation, they are large; but when crystallized from a very concentrated solution, or stirred during the process, they appear as fine needles, like those of Epsom salts (magnesic sulphate), with which zinc vitriol is isomorphous. They have a sharp metallic taste. Ordinarily the crystallized salt contains seven equivalents of water; but crystals can be formed with only six, five, two, and one.

At 100° C. (212° F.) six equivalents escape, the last equivalent going only at higher temperature. The number of parts of the sulphate dissolved by 100 parts of water at different temperatures is as follows:

The great increase in the solubility of the crystals at the higher temperatures is due to their melting in their own water of crystallization. Medicinally zincic sulphate is tonic, astringent; in large doses a prompt emetic; in over doses, an irritant poison, which, if not expelled by vomiting, may be counteracted with bland drinks in large quantities and the administration of opium. The solution is used externally as a styptic to bleeding surfaces, as a collyrium in diseases of the eye, as a gargle for ulcerated sore throat, and as an injection upon inner excoriated surfaces. It is used as a mordant in cotton printing, and as a dryer for oil paints. It is the substance from which numerous zinc compounds are prepared. Its property of decomposing at high temperature and leaving zincic oxide is made the basis of the preparation of the mixed zinc colors, in the various shades of which iron, manganese, cobalt, copper, nickel, and silver play a part. Zincic acetate is a medicinal preparation similar in properties and uses to the sulphate, and likewise employed as a mordant. - History. The ancient Greeks and Romans made brass from ores of zinc and copper, but were not familiar with metallic zinc.

Strabo speaks of a metal called "false silver," obtained by calcining and then melting with a certain earth a stone found near Andeira in the Troad. This metal, melted with copper, produced orichalcum, apparently the brass of the ancient Romans, of which the coins of the commencement of the Christian era are composed. Some imperial Greek coins of the 2d century also contain zinc, though the Greek bronze was usually made of copper and tin, occasionally with some lead. Pliny speaks of an ore called cadmia, used in the smelting of copper (probably a mixture of the carbonates or sulphides of copper and zinc), and describes the white, flocculent sublimate (pompholyx, zincic oxide) and the dense incrustation (spodos, now called cadmia or furnace calamine) forming upon the inner furnace walls when zincose ores are smelted. Sometimes the cadmia of Pliny appears to mean either natural calamine or furnace calamine. This confusion is found in other ancient writers, and is not unnatural, considering the stony appearance of the latter product, and the circumstance that both were found to yield with copper the same alloy. Festus (writing at some time between about A. D. 100 and 400) says: Cadmia, terra quoe in oes conjicitur, ut fiat orichalcum.

Ambrose, bishop of Milan, writes similarly in the 4th century. Beckmann cites Aristotle and Strabo concerning an ore of this nature, used for making brass, and Dioscorides and Galen as to the artificial product, which in their time was used medicinally, particularly in ophthalmic diseases. The term tutia (whence our tutty, as from cadmia our calamine), used in the 11th century by Avicenna, was similarly applied by the Greeks and Arabians to both the artificial and natural compounds rich in zincic oxide. Zosimus (a writer of the 5th century, as Beckmann supposes) prescribes the smelting of Cyprus copper and strewing of pounded tutia over it, to make brass; and the alchemist Hermes taught the use of tutia (of which he speaks as an artificial product from copper-smelting furnaces) in the transmutation of metals, for giving a gold color to copper. Yet in Germany the nature of furnace calamine seems to have been unknown or forgotten, until in the 16th century Erasmus Ebener showed that the vast quantities of it which had accumulated at the Rammelsberg furnaces might be used instead of native calamine in the manufacture of brass. The general ignorance of metallic zinc, coupled with such ancient and general use of its oxide and alloys, was due to its volatility and oxidability.

It was at Goslar, near the Rammelsberg, in the Hartz, that the Dominican monk Albertus Magnus, in the 13th century, obtained the metal, which he called marchasita aurea. Paracelsus, who died in 1541, first described it distinctly, and called it zinc (probably from zinke, a nail, in allusion to its crystalline fracture). He knew of it only as produced in Carinthia. Agricola (about 1550) speaks of the Goslar zinc as liquor candidus, or, in German, conterfey; and Fabricius, who died in 1571, conjectures that stibium is what the miners call cincum, which can be melted but not hammered. The alchemists, attracted by its property of giving a golden color to copper, probably expected great things from it, and sought to keep its nature secret. As late as 1617 it appears to have been an accidental product only of the Goslar furnaces, and in great request among the alchemists. Löhneysen says a metal called zinc or conterfelit, resembling tin, but harder and less malleable, collected in crevices under the melting furnace, where the stones were not well plastered. A few ounces, or at most two pounds, could be obtained at one time. Henkel is named by Beckmann as the first who intentionally manufactured zinc from calamine.

This was probably in 1721. By 1737 the manufacture was in successful operation in England, where it was invented by Dr. Isaac Lawson, a Scotchman. A. von Swab, of the Swedish council of mines, distilled zinc from calamine in 1742. Works were established at Bristol in 1743 by John Champion, who took out a patent in 1758 for the use of blende. His process was the destillatio per descensum, described below. Calamine brass had been made in Surrey a century before. The production of zinc in the East Indies is of still earlier date. As "Indian tin," or speautre (whence "spelter"), it was imported into Europe by the Dutch, who, it is said, captured a cargo of it from the Portuguese before 1640. It is vaguely referred to as coming from China, Bengal, Malacca, and the Malabar coast. According to Raynal, the Dutch East India company purchased annually in the latter part of the 18th century, at Palembang, 1,500,000 lbs. of zinc. The process of extracting it from its ores is said to have been brought to Europe by an Englishman, who went to India to discover the secret. - The first zinc produced in the United States was made about 1838, at the United States arsenal in Washington, from the red oxide of New Jersey, for the brass designed for standard weights and measures ordered by congress.

The process proved so expensive as to discourage for a long time the idea of treating this ore. The regular manufacture was first undertaken at the works of the New Jersey zinc company in 1850. The Belgian plan, first adopted, failed by reason of the chemical sction of the ore upon the retorts. The oxide of iron in the franklinite, associated with the red zinc ores, was particularly injurious, forming a fusible silicate with the silex of the clay. The Silesian plan, tried in 1856 by Matthiessen and Hegeler at the works of the Lehigh company, also proved a failure. Samuel Wetherill of Bethlehem, Pa., attempted to produce spelter by treating zinc ores in open furnaces, the oxidized vapors being drawn through incandescent anthracite to reduce the oxide. Joseph Wharton is said to have experimented on a somewhat similar plan at Camden, N. J., but the idea cannot be said to have proved practicable, though Mr. Wetherill, who obtained a patent for his process, made a few tons of zinc. He subsequently recommenced the business, using upright retorts, and succeeded in obtaining materials and devising a mixture sufticiently refractory for his purpose.

This important desideratum being secured, the Lehigh zinc company, of which Mr. Wharton was manager, returned to the Belgian furnace, importing a metallurgist and skilled workmen, and finally in 1860 constructed works at Bethlehem, where it still carries on the process. Meanwhile the manufacture of zinc white, which involves less difficulty and loss, and for which the purity of the Pennsylvania and New Jersey ores and the smokeless combustion of anthracite afford the necessary conditions, was successfully carried on by both the New Jersey and Lehigh companies, according to a plan invented by Mr. Wetherill. Spelter ingots and rolled sheet zinc are now manufactured in the United States by a considerable number of establishments, enumerated below. - The chief deposits of zinc ores in Europe are in Silesia and Oarinthia, and near Liege in Belgium, particularly the mine of Vieille-Montagne or Altenberg, between Liége and Aix-la-Chapelle. Spain, Sweden, Great Britain, and other countries also furnish either calamine or blende. It is said that Swedish ores are now taken to VieilleMontagne, the deposit there being partially exhausted.

The chief deposits in the United States are those of calamine and blende at Friedensville, Lehigh co., Pa., in the lower Silurian magnesian limestone, the red oxide deposits of New Jersey in the same rock, the calamine deposits near Knoxville, Tenn., and in Arkansas, the calamine and blende deposits of the Silurian rocks of S. W. Wisconsin, and the subcarboniferous rocks of S. W. Missouri. - Metallurgy. There are four principal ores of zinc, viz.: 1, the carbonate (smithsonite, formerly called calamine), containing when pure 52 per cent, of zinc, white or pale yellow or green, vitreous to resinous in lustre, of sp. gr. 4.2, hardness 4.5, crystals rhombohedral; 2, the silicate, which is either anhydrous (willemite), containing 58 per cent, zinc, white, gray, or pale yellow, of vitreous lustre, sp. gr. 4, hardness 5.5, crystals hexagonal; or hydrous (calamine or electric calamine), white or pale yellow, of vitreous lustre, sp. gr. 3.16 to 3.9, hardness 4.75, crystals hemihedral; 3, the sulphide (sphalerite, zinc blende), 66.9 per cent, zinc, yellow, red, brown, or black, rarely green or white, of adamantine lustre, sp. gr. 4, hardness 4, brittle, crystals isometric, containing as accidental constituents iron, cadmium, oopper, manganese, antimony, and lead, in traces; 4, the oxide (zincite, red zinc ore), 80.2 per cent, zinc, deep red to orange yellow, of subadamantine lustre, sp. gr. 5-5, hardness 4, brittle, crystals hexagonal, occurring exclusively in the neighborhood of Franklin, N. J., and usually mixed with willemite, franklinite, and magnetite.

To these natural ores may bo added artificial zinciferous by-products, such as furnace calamine, zinc crusts from desilverizing processes, etc. - The. manufacture of zinc is essentially a reduction, by means of carbon, of the zincic oxide, formed by a preliminary calcination of the ore. Since the temperature at which the oxide is reduced is about 1300° 0. (2372° F.), or near the fusing point of cast iron, while the zinc melts at 412° 0. and boils at 1200° C, the metal when reduced is a vapor, which by cooling is condensed into a liquid. Hence the distillation is performed in retort furnaces, which must be of the best fire-proof material. The price of fuel, its nature (giving long or short flame), the price and quality of clay, and the nature and purity of the ore, control the choice of methods and apparatus from among the three chief forms about to be described. A special difficulty in the manufacture arises from the property of the metal at nearly the temperature of its reduction to become oxidized again in the presence of carbonic acid, the formation of which cannot be entirely avoided.

By heating zincic oxide and carbon, zinc and carbonic oxide are formed, the latter of which, acting upon another portion of zincic oxide, reduces it to metal and itself becomes carbonic acid. At sufficiently high temperature, this carbonic acid is again reduced to oxide by another portion of the carbon; but if the temperature falls to a certain degree below white heat, the carbonic acid is reduced by the metallic zinc vapors instead, oxidizing these in turn to zincic oxide. Hence the retorts should not be allowed to cool during distillation. In order that the zinc vapors passing out of the retorts into the nozzles or condensers may be as little as possible oxidized by air and carbonic acid there present, the latter vessels must be kept so cool (say 400° C= 752° F.) that the zinc may at once become liquid; but in spite of this, a portion is oxidized, causing loss and extra expense in the repeated reduction of the oxide. Too much cooling of the nozzles, or too slow generation of the zinc vapors, causes the formation, instead of liquid zinc, of a zinc powder, which must be transformed into bars at further expense and loss. Metals more volatile than zinc, particularly cadmium and lead, pass over chiefly at the commencement of the process, and are caught in vessels beyond the nozzles.

Aqueous vapor oxidizes energetically the vapors of zinc. The operations preliminary to distillation are calcination, crushing, and the preparation of the charge. Calcination is applied to the carbonate and silicate ores to expel carbonic acid and water, and to facilitate by the disintegration of the ore the subsequent action of carbonic oxide gas. For this purpose kilns may be used, in which the ore (in fragments) is either played upon by flame, or is charged in alternate layers with the fuel. The latter method saves fuel and gives a more uniform result, but may involve a reduction and volatilization of zinc when the fuel is in excess, and also adds to the ore the impurities contained in the cinder and ashes of the fuel. For finely crushed ore reverberatories are employed. The practice, formerly common, of using the waste gases from the distilling furnaces to heat the calcining furnaces, or even, as in the old Silesian furnaces, of building chambers for calcination in the same furnace, in another part of which distillation was conducted, is now pretty generally discarded, as interfering with the proper control of the latter and more delicate operation. The roasting of zinc blende has for its special object the removal of sulphur and the formation of zincic oxide.

Owing to its density, this ore must in general be reduced to grains of one to two millimetres diameter, though a preliminary calcination of fragments may be performed in open heaps or kilns; and there are a few varieties of blende (like some light-colored, massive blendes of the Rhine provinces) which, once ignited, burn of themselves, and may hence be easily roasted by the ruder method. Usually, however, even the finely crushed blende yields its sulphur with difficulty, because the sulphate which is formed decomposes at white heat only. The best practice, under ordinary circumstances, leaves 1 to 2 per cent, of sulphur in the charge, since to remove this remnant would involve a disproportionate consumption of fuel and an increased loss of zinc in roasting. The sulphur remains either in undecomposed sulphides or as sulphate. At the Lehigh works, Bethlehem, Pa., 40 per cent, of coal dust is mixed with the blende in roasting, but 1 or 2 per cent, of sulphur still remains. The chief inferiority of zinc blende as an ore to the carbonate, silicate, or red oxide lies in the greater cost of the roasting as compared with the calcination of the latter ores. About nine times as much fuel is required per unit of zinc subsequently produced.

Moreover, the usually greater impurity of blende, and the higher temperature required in its treatment, cause the presence of a larger amount of metallic oxides (iron, lead, manganese, &c), which both attack destructively the retorts and yield a final product of inferiof quality. This is not the case with exceptionally pure blendes. The choice of apparatus for roasting blende is determined to some extent by the utilization of the sulphurous acid vapors. If these are to be transformed into sulphuric acid, muffle furnaces, or the inclined furnace of Hasenclever, or the upright terrace furnace of Gerstenhofer (Stetefeldt's showering furnace has also been recommended), may be employed. The Hasenclever furnace, in its latest form, with which the name of Hilbig also is associated, is used at several European works. In the accompanying sectional sketch, i is the hopper into which the ore is charged; s, an inclined channel, depressed 43° from horizontal, 1.8 metre wide, 0.5 metre high, and 9 metres long, heated from below by the flame in the flue d from around the muffle furnace b; h, h, 50 partitions, which stop short several centimetres above the inclined floor, forcing the ore to descend in a thin layer, while the gases from the muffle, b, passing through openings placed zigzag in these partitions, are made to traverse the surface of the ore for a long distance, and finally allowed to escape at s, loaded with sulphurous acid.

The inclined channel and the flues are accessible through side doors. At g is a hollow, air-cooled, revolving feeder, operated periodically by a water power, at each turn of which a certain amount of ore is taken from the bottom of the incline and pushed into the muffle, while the layer of ore in the incline slips downward. Every two hours the ore is spread out in the muffle by hand, through working doors, and gradually pushed to the back, where it falls through an opening upon the hearth a, heated by direct flame. Here it is completely roasted, the last portions of sulphurous acid escaping with the gases of combustion through e, c, d, and m into the stack. The Boetius gas producer Z, and the air supplied at n, give an economical heat to the hearth, the working door of which is at f. It will be seen that this arrangement keeps the flame gases, smoke, etc,: separate from the charge till the roasting is nearly complete, and thus furnishes sulphurous acid gas of greater purity (escaping ats) for the manufacture of sulphuric acid. The gas passes from s first into a cooling chamber, on the iron top of which ore is dried, thus completing the utilization of the heat. Even blende poor in sulphur (which is the hardest to roast) can be successfully treated in this apparatus.

A blende containing 20 per cent, of sulphur when charged was found to contain at g 10 per cent., at the back side of b 6.4 per cent., and at the fire bridge of a (just before withdrawal) 1*2 per cent. The further dimensions of the furnace are, in metres: muffle, 5, 6.5 long, 1.8 wide, 0.4 high, with five working doors on one side; hearth, a, 5 7 long, 0.4 high; generator, l, 1.5 high, 0.5 broad at the bottom, 1.4 at the arch. This furnace is a good example of the modern improvement of combining the muffle and the reverberatory, neither of which is perfectly satisfactory alone, since the former furnishes usually a dilute gas for the sulphuric acid chambers, with a relatively large consumption of fuel, and effects an incomplete roasting, while the latter contaminates the sulphurous acid with flame gases and smoke. Nevertheless, the reverberatory is still largely employed, especially with two hearths disposed one over the other, or at different levels side by side, to permit the more complete utilization of heat and the gradual advance of the ore to hotter zones. Very long reverberatories are sometimes employed for the same purpose.

Blende is crushed fine before roasting; other zinc ores, which have been calcined in lumps, are crushed likewise, preliminary to distillation, finer for the Belgian than for the Silesian process. The crushing apparatus for hard ores may be rock breakers, rollers, &c; for softer material, grinding or Chilian mills, or centrifugal pulverizers. The preparation of charges for distillation consists in mixing the calcined ore with a proper proportion (sometimes 100 per cent, but usually 40 to 46 per cent, for calamine, and 55 to 60 per cent, for blende) of lean coal, as free as may bo from pyrites and slate. It is well to substitute coke for half the coal, since coke forms no water, and thus diminishes that cause of the production of zinc powder. But coke alone is said to reduce less powerfully and to require a higher temperature. The distillation of zinc from the oxidized ores is always conducted in muffles (Silesian method), retorts (Belgian method), or crucibles (old English method), and hence involves much consumption of fuel and destruction of refractory material. Great losses of metal are also unavoidable, ranging from 9 to over 30 per cent, of the zinc in the charge.

All attempts to reduce the cost of distillation by employing shaft furnaces, reverberatories, or very large muffles have hitherto failed, by reason of their production of zinc powder or zincic oxide, or both, which must after all be treated in retorts, to obtain liquid zinc. - The old English method is a distillation per descensum, the ore being charged into crucibles placed in a circle about a central fire and under an arch. These crucibles are covered, and the zinc vapors, formed by heating, are obliged to pass down through the charge and by openings in the bottom of the crucibles, to be condensed below. The capacity of such furnaces is small, the emptying of the crucibles inconvenient, the destruction of fire clay comparatively light, and the consumption of fuel very great (22 to 27 parts of fuel for one part of zinc produced). For these reasons the process is now generally abandoned, except for the redistillation of zinc residues, in localities where fire clay is dear and coal is very cheap. - The Silesian and Belgian methods are now chiefly followed.

The former employs muffles, and, according as the flame outside of the muffles is allowed to escape freely upward into the air through openings in the arch, or is conducted downward through openings in the hearth to a chimney, the process is known as the old Silesian or the Belgian-Silesian. The Belgian system employs cylindrical retorts, placed in rows, gently inclined, in the furnace. The old Silesian furnace consists of a square, arch-covered hearth, with a depressed fire box in the middle, on both sides of which muffles are arranged in rows Such a furnace may contain 20 to 26 muffles, averaging 3 ft. 7 in. in length, about half as much in height, and a quarter as much in width. Lean coal, giving a short flame, is burned on the grate, and the flame plays around the muffles, subsequently escaping, either through openings in the arch, or through side openings into chambers for "tempering" muffles, calcining ore, or remelting zinc. The zinc vapors from the muffles escape through elbow-formed nozzles and fall, condensed into drops, into receptacles, where they congeal, to be subsequently remelted and cast into bars. The residues, withdrawn from the muffles, fall on the floor of the works, and, together with the gases and smoke escaping from the top, cause much inconvenience to the workmen.

Moreover, the fuel consumption is large (17 parts to one part of zinc produced), and the total loss of zinc may reach more than 30 per cent. Charging fresh ore into the adjoining calcination chambers may cool down the distilling space injuriously, as may also the necessary poking of the coals, or opening of the furnace door to promote combustion, there being no chimney to give a draft. The addition of a chimney, on the other hand, is said to cause with certain coal, like the lean coal of Silesia, too quick a combustion; and moreover the draft causes a leakage of zinc vapors through defective places in such muffles as are nearly worn out. The muffles are made with care of fire clay and "chamotte" (coarsely pulverized old muffle material), kneaded and moulded by hand or machinery. The imperfections of this process have not prevented its continued use in Silesia, where habit and skill, cooperating with local conditions, seem to permit its employment with fair results. The charge per 24 hours for a 20muffle furnace (apparently the best type) is 750 to 800 kilogrammes of calamine; duration of muffles, six to eight weeks.

The following are the stages of the process of distillation: careful drying and heating of the furnace; introduction of the glowing muffles from the tempering chamber, and placing of them upon a bed of sand in the hearth; filling of spaces where the flame is not to pass with clay and fragments of brick; attachment of the nozzles; plastering of all cracks with loam; gradual charging with long semi-cylindrical spoons, through openings in the elbows; closing of these and other openings; accumulation for the first two or three hours of zinc powder in the cold necks or nozzles, and its removal by means of an iron wire; white heat in the furnace and an increasing production of drops of zinc for six or eight hours; maintenance for an equal period of the maximum flow; gradual diminution after 24 hours from charging; opening of the furnace, and removal of the liquid zinc to a cooler space; raking out of the residues, scraping, repairing, or replacing of muffles; fresh charge; remelting of the zinc in iron kettles.

In the Belgian-Silesian method, a long flame strikes from the fire box against the arch, reverberates around the muffles back to the hearth, and is drawn through openings in the latter into a flue below, which leads either direct to the chimney or to calcining chambers.

Fig. 1. - Hasenclever Furnace.

This arrangement more completely utilizes the fuel, and reduces the consumption of coal to from six to eight parts for one part of zinc •produced. The production is also increased, and the annoying smoke is removed. The long flame permits an increase of the number of muffles to 40; and by the use of gas as fuel (see below) as many as 136 have been heated successfully in a single furnace. The nozzles are made like those in the Belgian retort furnaces, so that the zinc, instead of issuing in drops, and requiring to be remelted afterward, flows at once into moulds, with less loss by oxidation. What zinc powder is formed is mostly caught in balloons attached to the extremity of the nozzles. The residues fall, when the furnace is cleaned out, through slits into ash pits, from which their vapors are conducted away through flues. A great improvement in this variety of the Silesian process has been effected by the use of gas producers instead of ordinary grates. The Siemens regenerative gas furnace has been adapted for the purpose, with the advantages of a great gain in fuel, and an increased durability of the muffles, which carries with it a diminution both in the cost of repairs and in the leakage of vapors.

On the other hand, this apparatus requires large expenditure in construction, careful adjustments, and skill and faithfulness in attendance. Zinc oxide, which accumulates in the regenerators, requires to be removed. The Siemens apparatus, invaluable for metallurgical operations requiring the very highest temperatures, can be advantageously replaced in the present case by the simpler gas producer of Boetius, shown above in connection with the Hasenclever furnace. The general operations of distillation by the Belgian-Silesian method resemble those of the old Silesian, except as to the liquid zinc, mentioned above. The following examples will show the economy of the process: 1. Furnace with ordinary grate (requiring a long-flame coal): 24 muffles; daily charge, 580 kilos of calamine, containing 50 per cent, zinc, of which 39.2 per cent, is obtained; consumption of coal for reduction, 150 kilos; for fuel, 1,808 kilos; 0.4 muffle and 2 nozzles destroyed daily. The consumption of fuel is to the product of zinc about as 8:1. 2. Furnace with Siemens regenerators: 72 muffles; duration of campaign, 2,798 days; daily destruction of muffles, 1.1; ore treated daily per muffle, 28.24 kilos; zinc produced, 11.18 kilos; percentage of zinc in ore, 48; of yield, about 42 per cent. (i. e., a loss of about 13 per cent, of the zinc in the ore); consumption of fuel per unit of zinc, 5.34 units. 3. Furnace with Boëtius producer: 136 muffles; ores containing 50 per cent, yield 41 per cent, of zinc; proportion of fuel to zinc, 5 to 6: 1. - The Belgian system of distillation is conducted in inclined cylindrical retorts, disposed in rows above the. fireplace, and provided with fireclay nozzles or condensers, over the outer ends of which conical tubes (balloons, caps, or "prolongs") of sheet iron are placed during the operation.

The ordinary form is shown in fig. 2, which presents a section from front to rear. In this furnace the eight retorts, a', of the lowest row are left empty, to serve as "protectors" and regulators of the temperature, by means of openings in them, through which the flame may be drawn at will. Above them are 61 useful retorts, a. A very important matter in this process is the manufacture of the retorts, which are formed from a carefully prepared mass of clay, chamotte (dried or burnt clay in sharp fragments), and water, kneaded, and after some weeks rekneaded, etc. Coke powder may be added, to give solidity, imperviousness to zinc vapors, and smooth surface. A good composition, used at Engis, is 30 raw clay, 27 chamotte, 18 coke, 15 old retort material, 10 sand. From this mass the retorts are formed either by machinery (a core being pressed into a mould filled with the material, or the clay being pressed over a mandrel, as in the manufacture of lead pipes, or massive cylinders of clay being bored out), or by hand, in various ways, the best of which, at least for some materials, appears to be the building up of the retort, like a circular tower, by winding spirally around its upper edge a succession of long rolls of plastic clay.

This is the method in the Lehigh works at Bethlehem, Pa. The proper drying of the retorts requires months, the longer the better. It is performed in large heated chambers. They are highly heated just before use, and are introduced glowing into the furnace. Eecently more silicious materials (up to 94 per cent, silica) have been employed in Belgium, with gain in durability and saving of cost. The stages of the distillation are as follows: The furnace is gradually heated for two days, the retorts being empty. (The material of the retorts first put in, at the beginning of a campaign, should contain no coke or anthracite, since this would burn up while the retorts were thus heated empty.) The charges are then gradually introduced by means of semi-cylindrical spoons, the nozzles being removed for this purpose. The lower rows of retorts are most heavily charged with ore. The furnace attains its full productive capacity on the 13th or 14th day. After charging, the condensers are attached, and when the zinc flame makes its appearance through these, the sheet-iron prolongs are added. The liquid zinc is drawn from the condensers at intervals into ladles, skimmed, and cast into ingots.

When the distillation in each retort is complete, the condenser is removed and cleaned, and the residues are scraped out of the retort. A row can be emptied in 10 to 15 minutes. The residues from the uppermost are the richest. The retort is then patched or replaced, if damaged. The destruction of the furnace ends the campaign. The following examples show the working of the process: 1. Engis. New double furnace, 92 retorts; day charge, 400 kilos ore (calamine and blende), 72 kilos rich scraps, and 166 kilos coal for reduction; night charge (the furnace being hotter), 500 kilos ore. Charging from 6 to 9.15 A. M. First tap at 1 P. M., second at 4.30, third at 6. Length of campaign, 150 to 180 days; production, 82,910 kilos zinc from 285,520 of ore, containing 40.32 per cent, zinc; loss, 11.28 per cent.; consumption for 100 kilos zinc produced, 5.8 hectolitres coal for fuel, 1'8 hectolitres coal for reduction; cost of treatment, 38.97 francs. 2. Other Belgian works. Furpaces with 70 retorts, taking 1,300 kilos of charge per 24 hours (ore containing 47 to 48 per cent, zinc), use 700 kilos of coal for reduction and 2,000 as fuel, and produce 470 to 480 kilos of zinc; say 18 per cent. gross loss, which is reduced by subsequent treatment of the residues.

New furnaces with 164 retorts produce in 24 hours 1,050 kilos of zinc with 4,000 kilos of fuel. Furnaces which are heated with gas producers yield the same quantity of zinc with 3,000 kilos of fuel. As compared with the Silesian process, the Belgian requires less fuel, but a longer flame, owing to the greater distance of the retorts from the fire; a larger quantity and more refractory quality of clay; a finely crushed charge; richer ores, on account of the expense for fuel and clay; and greater skill and endurance of workmen. On the other hand, it furnishes a more rapid and complete extraction. - The mines worked by the Lehigh zinc company are in Lehigh co., Pa.; in a valley from two to three miles broad, and four miles south of Bethlehem. The north and south boundaries of the valley are syeuitic hills, and between these a dolomitic limestone, underlaid by slate, Potsdam sandstone, and syenite, in downward order, is the outcropping rock. In this limestone the zinc deposits occur, in nearly vertical bodies, along an anticlinal axis. They comprise a massive light-colored blende of waxy lustre, and smithsonite and calamine, in pure, earthy, and argillaceous varieties, up to a compact, unctuous clay, containing from 26 to 32 per cent, of zinc.

The first discovery was made by Prof. "W. T. Roepper in 1845, and the property was bought by the present company in 1861, since when it has been regularly worked. About 80,000 tons of ore are extracted annually. The chief difficulty of mining is the large quantity of water, which flows underground in rivers into the mines, all the wells and surface streams of the neighborhood having been drained. At intervals since 1854 pumping engines of increased power have been erected, until in 1871. the climax was reached with the largest minepumping engine in the world, the diameter of the steam cylinder being 110 in. and the stroke 10 ft., the power at 60 lbs. steam 3,000 horse power, and the ordinary capacity at considerably lower pressure 17,000 gallons of water lifted per minute from a depth of 300 ft. The mechanical and metallurgical treatment of the ore is described in a paper in vol. i. of the "Transactions of the American Institute of Mining Engineers." The following is a brief outline. The blende is crushed in a Blake's crusher, and passed over a sieve with one mesh to the inch. The larger pieces, passing over the sieve, 'are separated by hand from gangue, and sent directly to the furnaces, or roasted in heaps of 50 tons.

The silicates and carbonates are washed and sized, and the larger pieces sent to the furnaces, the fine stuff being concentrated in buddies or jigs. For the manufacture of spelter, the heap-roasted and also the screened blende are thoroughly roasted in reverberatories, with the addition of 40 per cent, of coal dust. The silicates and carbonates are calcined in kilns, and then crushed with 40 per cent, of coal and sifted, before charging into the retorts. The ordinary Belgian process of distillation is employed. Each furnace contains 56 retorts, in seven rows, besides a bottom row of six protectors or " cannons," which are not charged. The retorts are 42 in. long, 9 in. exterior and 6 in. interior diameter, made of a mixture of fresh fire clay and ground fragments of old retorts, and provided with condensers or nozzles, 16 in. long, 6 in. diameter at the largest and 3 in. at the smallest end. The furnaces are in groups of four, with internal walls of fire brick and external of common brick lined with fire brick. The slant of the retorts varies with the quality of the ore, but is generally from 3 to 6 in. from the rear to the front.

Of the mixture of ore (47 per cent, zinc) and coal 40 lbs. is charged every 12 hours into each retort, except the upper row, which are charged every 24 hours with skimmings, etc, containing from 60 to 65 per cent, of zinc. As soon as zinc vapors are seen burning at the ends of the condensers, prolongs or conical caps of sheet iron are put on. Every 12 hours the zinc is collected in ladles and poured into ingot moulds, 7 by 24 by 1 in., containing 40 to 45 lbs. The chemical reactions are described as follows. The air introduced with the charge causes an imperfect combustion of a portion of the carbon present, forming carbonic oxide, which reduces oxide of zinc to a metallic state, and forms carbonic acid. There are then present in the retort, at a high temperature, oxide of zinc, carbon, and carbonic oxide. By the reduction of two equivalents of the former, one equivalent of carbonic oxide is converted into carbonic acid, and one of carbon into carbonic oxide; and so the process continues, repeating itself until the zinc oxide has been completely reduced.

Carbonate and silicate ores, containing 47 per cent, of zinc, yield actually from 34 to 35 per cent.; blende of the same richness yields 33 to 34 per cent., its smaller yield being due to the proportion of sulphur left in it, even after careful roasting. The spelter works deliver about 65 cwt. daily to the rolling mill, where it is remelted in a reverberatory and run into shallow moulds. Rolled down to the desired thickness, and annealed and trimmed, the sheets are packed in casks, containing 1,200 lbs. each. The same company manufactures zinc white. Its product since 1863 has been 47,191,829 lbs. of oxide and 34,983,717 lbs. of spelter; in 1875 it was 1,988,600 lbs. of oxide and 3fc370,641 lbs. of spelter. The New Jersey zinc company, having mines near Franklin, N. J., both of calamine and of red zinc ore, manufactures at its works in Newark oxide, spelter, and (from the residues of the zinc manufacture) franklinite iron and spiegeleisen. (See Franklinite.) The product of oxide and spelter by this company has been in 24 years, from January, 1852, to the end of 1875, 61,480 tons (of 2,000 lbs.) of oxide, and in 12 years, from May 17, 1864, to tire end of 1875, 5,980 tons of spelter.

The mines of this company are the most extensive and valuable zinc mines in the country, presenting a vein of great size and length, filled with massive ore (silicates, red oxide, and franklinite). The Passaic zinc company (mines at Ogdensburg, N. J., works at Communipaw, near Jersey City) began operations in 1855. The company works two veins, respectively 40 and 20 ft. wide, by open pits and cuts (present maximum depth, 180 ft.), extracting 5,000 or 6,000 tons of silicate and oxide per annum. The (Belgian) spelter furnaces are in two stacks of four each, back to back, 70 retorts in each furnace. There are also about 50 furnaces for making zinc white; and a rolling mill for sheet zinc was finished in 1876. The total product of oxide since 1855 has been between 30,000 and 35,000 tons, of which two thirds was produced within the last ten years. The spelter manufacture was begun in October, 1874, and about 900 tons had been produced down to the end of 1875. The best spelter of this company is exceedingly pure. The ores yield 36 per cent., which is said to be about 85 per cent, of the total quantity of zinc contained in them.

The-Bergen Port zinc company, at Bergen Port, N. J., manufactures spelter and oxide, employing for the former the Lehigh ore, from a mine adjoining that of the Lehigh zinc company at Friedensville, Pa. The product in 1875 was 500 tons of spelter and 1,000 tons of oxide. - An important centre of zinc production in the United States is La Salle, 111., where several establishments treat the ores (both blende and calamine) of the Mississippi valley, which are brought to this point on account of the availability of cheap coal. The most important works are those of the Matthiessen and Hegeler zinc company, which were first established in 1857, the earliest west of the Alleghanies, except an unsuccessful furnace at Mineral Point, Wis. This company manufactures spelter and sheet zinc, in gas furnaces built after a special design of the proprietors, and strictly neither Silesian nor Belgian in principle. The product in 1874 was 8,108,062 lbs. of spelter; in 1875, 7,845,992 lbs. of spelter* (7,412,132 lbs. of sheet zinc, principally made from the spelter produced at the works). In 1867 the product was a little over 2,000,000 lbs. of spelter (sheet zinc, about 2,000 lbs.). It has steadily increased since.

The La Salle (formerly the Mineral Point) zinc company has six Belgian furnaces, containing 82 to 96 retorts each, and a rolling mill started in October, 1875. The works of Robert Lanyon and co., at La Salle, comprise four Belgian furnaces; those of the Illinois zinc company, at Peru, near La Salle, have the same capacity. The ores employed by all these works are chiefly carbonate and blende, associated with lead ore (principally galena), iron pyrites, and iron oxides, from S. "W. Wisconsin. Blende and carbonate, and, by the Illinois company in particular, hydrous silicate, are also brought from Missouri. The Chicago zinc and mining company," at Cherokee, Kansas, has four Belgian furnaces, of 102 retorts each. The mines are in Newton co., Missouri, and yield blendecontaining 50 to 60 per cent., and silicate containing 30 to 40 per cent, of zinc. The works began running about the beginning of 1874, and have produced annually about 2,000,000 lbs. of spelter. The Martindale, Missouri, and Carondelet companies, at St. Louis, complete the list of the producing works of the United States. There are some establishments which buy spelter for the manufacture of sheet zinc.

None of the western works manufacture zinc white, this being produced from the purer ores of the east. - The manufacture of metallic zinc in the United States is shown by the following table, compiled by Messrs. Behr and Steiner of New York from the returns of the various works. The figures given include the amount of metal rolled into sheets.

Fig. 2. - Section of Belgian Furnace.

The importations of Silesian spelter, which have averaged 3,400 tons per annum since 1862, amounted in 1875 to only 540 tons. The total annual product of zinc in Europe is over 150,000 tons, of which about half is produced in the German empire. - Zinc White. The use of zinc oxide as a substitute for white lead was first suggested by Courtois, a manufacturer of Dijon, near the close of the last century. M. Leclaire, a house painter of Paris, some years later devised a cheap method of producing it, by heating zinc in retorts and exposing the escaping vapors to a current of air, drawn by a chimney or exhausting fan through the condensing apparatus. He also prepared a drying oil suitable for its use, by boiling linseed oil with about 5 per cent, of oxide of manganese, and furthermore substituted new yellow and green unchangeable pigments for the poisonous ones containing lead, copper, or arsenic. The chief excellence of zinc white is its brilliant lustre and its freedom from' discoloration when exposed to sulphuretted vapors, which turn lead paint black. Magnesia, or a mixture of the chloride and sulphate of zinc in small proportions, may be boiled in linseed oil, instead of manganese, to form a suitable drying oil.

The Europeans still employ metallic zinc for this manufacture, and by selecting the purest spelter make the best varieties of zinc white. Such is the blanc de neige or "snow white " of the French, used by painters instead of "silver white." The ordinary zinc white, and" stone gray" and "gray oxide" of the English, are less pure. Stone gray is used as a ground color for walls, iron work, etc, and gray oxide for painting ships and as a ground cojor on stone or cement. The manufacture of zinc white from natural oxide or oxidized ores can only be practised with pure materials and a smokeless fuel. The following outline of the process as carried on at the Lehigh works, Bethlehem, Pa., will suffice as an example. The ores used for this purpose (20 per cent, zinc) are mixed with 50 per cent, pea or dust coal, rolled, and screened; and the fine and coarse ores are treated separately though similarly. The furnaces are single or double reverberatories, in which the charge is placed on heavy rollediron grates, with perforations for the passage of air. The charge is, for the single furnaces (5 ft. by 3), 240 lbs. of ore, 120 lbs. of anthracite, and 100 lbs. of pea coal as a bed; for the double ores (16 ft. by 5), 640 lbs. of ore, 320 lbs. of coal, 240 lbs. of pea coal.

No fluxes are added, the object being to keep the charge from becoming impervious to the blast, which is furnished by four fan blowers. The process lasts four hours for each charge. A workman tends four furnaces, cleaning and charging one each hour. The chemical reactions give a curious instance of the performance of reduction and oxidation in the same furnace at the same time. The blast first oxidizes the lowest coal to carbonic acid, which, passing upward through the bed of coal, is reduced to carbonic oxide. This reduces the zincic oxide of the ore to metallic zinc, becoming itself carbonic acid again. The zinc volatilizes at the high temperature resulting; and its heated vapors, uniting with the carbonic acid, are again oxidized. The oxide thus formed is carried along a conducting channel over a sheet of water into a cooling tower, 75 ft. high and 80 ft. in circumference at the base. Much of the damp, impure oxide settles in this tower; the remainder is conveyed down another tower, 50 ft. high, and by an exhaust fan is forced through another channel, or cooling chamber floored with sheet zinc, on which another portion of impure oxide collects.

The remainder is carried forward by the draft into the bag room, where a large number of muslin bags, 30 ft. long are suspended vertically from the sheetiron tubes conveying the oxide. Through these bags the air and gases of the draft leak out, while the flocculent zinc-white powder is retained. The bags are shaken every four hours, and the oxide is removed. By a similar method the red oxide ores of New Jersey are manufactured into zinc white; and a few years ago a considerable amount of so-called Bartlett oxide, containing both zinc and lead, and highly recommended for paint, was manufactured from the ore of a mine in North Carolina, which consisted of an intimate mixture of galena and zinc blende, in fortunately suitable proportions. The mine is at present idle (1876), and the product, under that name, is no longer in market; but it is said that galena is now sometimes mixed with zinc ores, to produce an oxide superior to white lead for vulcanizing rubber and for painting surfaces exposed to the weather.

Zinc white is often mixed with barytes or white lead; and besides its use as paint, it has been applied as a mastic for metallic joints, as glazing for pottery, as enamel for papers and cardboards in place of lead or barium carbonate, and as an ingredient in artificial gems and glass instead of lead or other metallic oxides.