Zinc Sentence Examples

Zinc and marble are worked in the neighbourhood.

The principal mining product is mercury, extracted at Idria, while iron and copper ore, zinc and coal are also found.

The joists are covered with a waterproof material such as asphalt, lead, zinc or copper, the three last materials being usually laid upon boarding, which stiffens the structure and forms a good surface to fix the weatherproof covering upon.

For example, when metallic zinc is dissolved in dilute sulphuric acid with production of zinc sulphate (in solution) and hydrogen gas, a definite quantity of heat is produced for a given amount of zinc dissolved, provided that the excess of energy in the initial system appears entirely as heat.

There are important zinc works at Auby and St Amand (Nord) and Viviez (Aveyron) and Noyelles-Godault (Pas-de-Calais); there are lead works at the latter place, and others of greater irirportance at Couron (Loire-Infrieure).

Sodium amalgam or zinc and hydrochloric acid reduce it to lactic acid, whilst hydriodic acid gives propionic acid.

The manufactures comprise sheet-iron, boilers, zinc, brick and tiles, paraffin, petroleum, soap and candles.

Copper, lead and zinc are produced in small quantities, being found in fissure veins with gold and silver.

The molybdates may be recognized by the fact that they give a white precipitate on the addition of hydrochloric or nitric acids to their solutions, and that with reducing agents (zinc and sulphuric acid) they give generally a blue coloration which turns to a green and finally to a brown colour.

Iron, zinc and lead are found in the vicinity, and some coal is mined.

The principal manufactures are firearms, ironmongery, earthenware, woollen cloth, beer, stoneware, zinc goods, colours and salt; in the neighbourhood are iron and coal mines.

The output of zinc was 2,168,783 lb (valued at $127,958).

One of the neighbouring mines, the Proprietary, is the richest in the world; gold is associated with the silver; large quantities of lead, good copper lodes, zinc and tin are also found.

Copper and zinc have also been found.

With bromine in acetic acid solution at ordinary temperature, nicotine yields a perbromide, C10H10Br2N20 HBr 3, which with sulphur dioxide, followed by potash, gives dibromcotinine, C10H10Br2N20, from which cotinine, C10H12N20, is obtained by distillation over zinc dust.

Galena and other lead ores are abundant in veins in the limestone, but they are now only worked on a large scale at Mill Close, near Winster; calamine, zinc blende, barytes, calcite and fluor-spar are common.

Galena and other lead ores are abundant in veins in the limestone, but they are now only worked on a large scale at Mill Close, near Winster; calamine, zinc, blende, barytes, calcite and fluor-spar are common.

Besides lead, gypsum and zinc are raised, to a small extent; and for the quarrying of limestone Derbyshire is one of the principal English counties.

In the neighbourhood are lead, zinc and silver mines, and some 20 m.

The neighbourhood is rich in zinc and lead; and copper is also found.

Grapes, barley, esparto grass, dry figs, almonds and zinc are exported.

The mineral wealth of Carinthia is great, and consists in lead, iron, zinc and coal.

It is a strong acid, and dissolved in water decomposes carbonates and attacks iron and zinc.

The ores found here comprise silver-free galena, sulphate of zinc and calamine.

Ruthenium dichloride, RuC1 2, is obtained (in solution) by reducing the sesquichloride by sulphuretted hydrogen or zinc. It is stable in the cold.

The distribution of weight in chemical change is readily expressed in the form of equations by the aid of these symbols; the equation 2HC1+Zn =ZnCl2+H2, for example, is to be read as meaning that from 73 parts of hydrochloric acid and 65 parts of zinc, 136 parts of zinc chloride and 2 parts of hydrogen are produced.

The Egyptians obtained silver, iron, copper, lead, zinc and tin, either pure or as alloys, by smelting the ores; mercury is mentioned by Theophrastus (c. 300 B.C.).

The action of these acids on many metals was also studied; Glauber obtained zinc, stannic, arsenious and cuprous chlorides by dissolving the metals in hydrochloric acid, compounds hitherto obtained by heating the metals with corrosive sublimate, and consequently supposed to contain mercury.

Stromeyer detected a new metallic element, cadmium, in certain zinc ores; it was rediscovered at subsequent dates by other observers and its chemical resemblance to zinc noticed.

Richter in 1863, and of gallium, detected in certain zinc blendes by Lecoq de Boisbaudran in 1875.

If the hot bead is colourless and remains clear on cooling, we may suspect the presence of antimony, aluminium, zinc, cadmium, lead, calcium and magnesium.

To the filtrate from the aluminium, iron and chromium precipitate, ammonia and ammonium sulphide are added; the precipitate may contain nickel, cobalt, zinc and manganese sulphides.

The next group precipitate may contain the white gelatinous aluminium hydroxide, the greenish chromium hydroxide, reddish ferric hydroxide, and possibly zinc and manganese hydroxides.

The next group may contain black nickel and cobalt sulphides, flesh-coloured manganese sulphide, and white zinc sulphide.

The solution with ammonium sulphide gives a white precipitate of zinc sulphide.

Neumann, who, in 1831, deduced from observations on many carbonates (calcium, magnesium, ferrous, zinc, barium and lead) that stoichiometric quantities (equimolecular weights) of compounds possess the same heat capacity.

The industries of the Lake District include slate quarrying and some lead and zinc mining, and weaving, bobbin-making and pencil-making.

It is remarkable that even a small addition of zinc-white (oxide of zinc) to the reddish varieties especially causes a considerable diminution in the intensity of the colour, while dilution with artificial precipitated sulphate of lime ("annalin") or sulphate of baryta ("blanc fix") acts pretty much as one would expect.

The objection that a copper plate shows signs of wear after a thousand impressions have been taken has been removed, since duplicate plates are readily produced by electrotyping, while transfers of copper engravings, on stone, zinc or aluminium, make it possible to turn out large editions in a printing-machine, which thus supersedes the slow-working hand-press.

Owing to the great weight of stones, their cost and their liability of being fractured in the press, zinc plates, and more recently aluminium plates, have largely taken the place of stone.

The manuscript maps intended to be produced by photographic processes upon stone, zinc or aluminium, are drawn on a scale somewhat larger than the scale on which they are to be printed, thus eliminating all those imperfections which are inherent in a pen-drawing.

A third method consists in placing the specimen within bibulous paper, and enclosing the whole between two plates of coarsely perforated zinc supported in a wooden frame.

The zinc plates are then drawn close together by means of straps, and suspended before a fire until the drying is effected.

Bosnia is rich in minerals, including coal, iron, copper, chrome, manganese, cinnabar, zinc and mercury, besides marble and much excellent building stone.

The empire is rich in minerals, including gold, silver, lead, copper, iron, coal, mercury, borax, emery, zinc; and only capital is needed for successful exploitation.

Volta's cell consists essentially of two plates of different metals, such as zinc and copper, connected by an electrolyte such as a solution of salt or acid.

As an example of a fairly constant cell we may take that of Daniell, which consists of the electrical arrangement - zinc zinc sulphate solution copper sulphate solution copper, - the two solutions being usually separated by a pot of porous earthenware.

When the zinc and copper plates are connected through a wire, a current flows, the conventionally positive electricity passing from copper to zinc in the wire and from zinc to copper in the cell.

Zinc dissolves at the anode, an equal amount of zinc replaces an equivalent amount of copper on the other side of the porous partition, and the same amount of copper is deposited on the cathode.

This process involves a decrease in the available energy of the system, for the dissolution of zinc gives out more energy than the separation of copper absorbs.

But the internal rearrangements which accompany the production of a current do not cause any change in the original nature of the electrodes, fresh zinc being exposed at the anode, and copper being deposited on copper at the cathode.

Thus as long as a moderate current flows, the only variation in the cell is the appearance of zinc sulphate in the liquid on the copper side of the porous wall.

In spite of this appearance, however, while the supply of copper is maintained, copper, being more easily separated from the solution than zinc, is deposited alone at the cathode, and the cell remains constant.

Thus in the Daniell cell the dissolution of copper as well as of zinc would increase the loss in available energy.

But when zinc dissolves, the zinc ions carry their electric charges with them, and the liquid tends to become positively electrified.

Hence zinc can only dissolve when some more easily separable.

Plates of platinum and pure or amalgamated zinc are separated by a porous pot, and each surrounded by some of the same solution of a salt of a metal more oxidizable than zinc, such as potassium.

The concentration of the simple copper ions is then so much diminished that the copper plate becomes an anode with regard to zinc. Thus the cell - copper I potassium cyanide solution I potassium sulphate solution - zinc sulphate solution I zinc - gives a current which carries copper into solution and deposits zinc. In a similar way silver could be made to act as anode with respect to cadmium.

Hence, if we assume that, in the Daniell's cell, the temperature coefficients are negligible at the individual contacts as well as in the cell as a whole, the sign of the potential-difference ought to be the same at the surface of the zinc as it is at the surface of the copper.

Since zinc goes into solution and copper comes out, the electromotive force of the cell will be the difference between the two effects.

By both these methods the single potential-differences found at the surfaces of the zinc and copper have opposite signs, and the effective electromotive force of a Daniell's cell is the sum of the two effects.

It is a centre of the iron and steel industries, producing principally cast steel, cast iron, iron pipes, wire and wire ropes, and lamps, with tin and zinc works, coal-mining, factories for carpets, calcium carbide and paper-roofing, brickworks and breweries.

Sherard Cowper Coles patented a process in which, working with a high current density, a lead anode is used, and powdered zinc is kept suspended in the solution to maintain the proportion of zinc in the electrolyte, and so to guard against the gradual acidification of the bath.

The electro-deposition of brass-mainly on iron ware, such as bedstead tubes-is now very widely practised, the bath employed being a mixture of copper, zinc and potassium cyanides, the proportions of which vary according to the character of the brass required, and to the mode of treatment.

The colour depends in part upon the proportion of copper and zinc, and in part upon the current density, weaker currents tending to produce a redder or yellower metal.

An authority on precious stones, and especially the diamond, he succeeded in artificially making some minute specimens of the latter gem; and on the discovery of radium he was one of the first to take up the study of its properties, in particular inventing the spinthariscope, an instrument in which the effects of a trace of radium salt are manifested by the phosphorescence produced on a zinc sulphide screen.

Thus, a mixture of lead sulphate (45%) and oxide (44%) with some sulphide (8%), zinc and carbonaceous matter, is agglomerated by a heap-roast and then smelted in a slag-eye furnace with grey slag from the ore-hearth.

This is drawn off, cooled and filtered, and forms a white paint of good body, consisting of about 65% lead sulphate, 26% lead oxide, 6% zinc oxide and 3% other substances.

In 1842 Karsten discovered that lead could be desilverized by means of zinc. His invention, however, only took practical form in1850-1852through the researches of Parkes, who showed how the zinc-silver-lead alloy formed could be worked and the desilverized lead freed from the zinc it had taken up. In the Parkes process only 5% of the original lead need be cupelled.

When zinc is placed on the lead (heated to above the melting-point of zinc), liquefied and brought into intimate contact with the lead by stirring, gold, copper, silver and lead will combine with the zinc in the order given.

By the second addition of zinc most of the silver will be collected in a saturated zinc-silver-lead crust, which, when worked up, gives fine silver.

As this complete desilverization is only possible by the use of an excess of zinc, the unsaturated zinc-silver-lead alloy is put aside to form part of the second zincking of the next following charge.

A zincking takes 5-6 hours;1 1 5-2.5% zinc is required for desilverizing.

The liquated zinc-silver-lead crust contains 5-10% silver, 30-40% zinc and 65-50% lead.

Before it can be cupelled it has to be freed from most of the zinc, which is accomplished by distilling in a retort made of a mixture similar to that of the plumbago crucible.

The distillation of 1000 lb charge lasts 5-6 hours, requires 500-600 lb coke or 30 gallons reduced oil, and yields about to% metallic zinc and I% blue powder - a mixture of finely-divided metallic zinc and zinc oxide.

About 60% of the zinc used in desilverizing is recovered in a form to be used again.

The desilverized lead, which retains o 6-0.7% zinc, has to be refined before it is suited for industrial use.

The zinc and some lead are oxidized; part of the zinc passes off with the fumes, part is dissolved by the litharge, forming a melted mixture which is skimmed off and reduced in a blast-furnace or a reverberatory smelting furnace.

In the kettle covered with a hood the zinc is oxidized by means of dry steam, and incidentally some lead by the air which cannot be completely excluded.

A yellowish powdery mixture of zinc and lead oxides collects on the lead; it is skimmed off and sold as paint.

Here compounds of divalent lead have not yet been obtained; by acting with zinc ethide on lead chloride, lead tetraethide, Pb(C 2 IH Q) 4, is obtained, with the separation of metallic lead.

The reaction is a general one for all aldehydes with zinc methyl and zinc ethyl, but not with the higher zinc alkyls.

Its chief mineral products are coal, nitre, sulphur, alum, soda, saltpetre, gypsum, porcelain-earth, pipe-clay, asphalt, petroleum, marble and ores of gold, silver, mercury, copper, iron, lead, zinc, antimony, cobalt and arsenic. The principal mining regions are Zsepes-Giimor in Upper Hungary, the Kremnitz-Schemnitz district, the Nagybanya district, the Transylvanian deposits and the Banat.

Small up to the beginning of the 19th century, Holywell has increasingly prospered, thanks to lime quarries, lead, copper and zinc mines, smelting works, a shot manufactory, copper, brass, iron and zinc works; brewing, tanning and mineral water, flannel and cement works.

The mother liquor includes generally more or less of nickel, cobalt, zinc and other heavy metals, which, as Wailer showed, can be removed as insoluble sulphides by the addition of ammonium sulphide; uranium, under the circumstances, is not precipitated by this reagent.

A strip of metallic zinc when placed in a solution of stannous chloride precipitates the tin in crystals and takes its place in the solution.

When heated with zinc dust, it yields ethylene and water.

The mineral wealth is great, including copper, tin, lead, zinc, iron and especially coal.

Bernthsen (Ann., 1884, 224, p. 1) condensed diphenylamine with fatty acids, in the presence of zinc chloride.

The newer glasses, on the other hand, contain a much wider variety of chemical constituents, the most important being the oxides of barium, magnesium, aluminium and zinc, used either with or without the addition of the bases already named in reference to the older glasses, and - among acid bodies - boric anhydride (B20 3) which replaces the silica of the older glasses to a varying extent.

The materials are generally used in the form either of oxides (lead, zinc, silica, &c.) or of salts readily decomposed by heat, such as the nitrates or carbonates.

The oxides of lead, barium, zinc and antimony are found perceptibly to retard the rays.

Wohler, Ann., 1856, 97, p. 266; 1857, 102, p. 382); by heating silica with magnesium in the presence of zinc (L.

The organic derivatives of silicon resemble the corresponding carbon compounds except in so far that the silicon atom is not capable of combining with itself to form a complex chain in the same manner as the carbon atom, the limit at present being a chain of three silicon atoms. Many of the earlier-known silicon alkyl compounds were isolated by Friedel and Crafts and by Ladenburg, the method adopted consisting in the interaction of the zinc alkyl compounds with silicon halides or esters of silicic acids.

Triethyl silicol, (C2H5),Si OH, is a true alcohol, obtained by condensing zinc ethyl with silicic ester, the resulting substance of composition, (C2H5)3 SiOC2H51 with acetyl chloride yielding a chloro-compound (C2H5)3SiC1, which with aqueous ammonia yields the alcohol.

Many are found as minerals, the more important of such naturally occurring carbonates being cerussite (lead carbonate, PbC03), malachite and azurite (both basic copper carbonates), calamine (zinc carbonate, ZnCO 3), witherite (barium carbonate, BaCO 3), strontianite (strontium carbonate, SrC03), calcite (calcium carbonate, CaC03), dolomite (calcium magnesium carbonate, CaCO 3 MgCO 3), and sodium carbonate, Na 2 CO 3.

It is easily broken down by many substances (aluminium chloride, zinc chloride, &c.) into ethyl chloride and carbon dioxide.

Water, at ordinary or slightly elevated temperatures, is decomposed more or less readily, with evolution of hydrogen gas and formation of a basic hydrate, by (I) potassium (formation of KHO), sodium (NaHO), lithium (LiOH), barium, strontium, calcium (BaH 2 O 2, &c.); (2) magnesium, zinc, manganese (MgO 2 H 2, &c.).

Of the rest, the following are readily oxidized by steam at a red heat, with formation of hydrogen gas - zinc, iron, cadmium, cobalt, nickel, tin.

Iron, zinc, cadmium, also tin under certain conditions, reduce the dilute acid, partially at least, to nitrous oxide, N 2 0, or ammonium nitrate, NH4N03.

The most important of these are aluminium and zinc, which are converted into aluminate, Al(OK,Na) 3, and zincate, Zn(OK,Na) 2, respectively.

Potassium, for example, yields peroxide, K202 or K204; sodium gives Na202; the barium-group metals, as well as magnesium, cadmium, zinc, lead, copper, are converted into their monoxides MeO.

There are also iron, zinc and chemical manufactures, and the cultivation of agricultural seeds is carried on.

On warming the osazone with hydrochloric acid the phenylhydrazine residues are removed and an osone results, which on reduction with zinc and acetic acid gives a ketose.

It also results on condensing acetylene, and on reducing phenylacetylene by zinc dust and acetic acid.

Zinc as a component of brass (XaXKOs, 6pei-XaXKos) had currency in metallurgy long before it became known as an individual metal.

Pliny explicitly speaks of a mineral Katiµ€ia or cadmic as serving for the conversion of copper into aurichalcum, and says further that the deposit (of zinc oxide) formed in the brass furnaces could be used instead of the mineral.

Moreover, zinc and bismuth were confused, and the word spiauter (the modern spelter) was indiscriminately given to both these metals.

From his account it is quite clear that that metal was zinc, but he did not recognize it as the metal of calamine.

It is not known to whom the discovery of isolated zinc is due; but we do know that the art of zinc-smelting was practised in England from about 1730.

Zinc does not occur free in nature, but in combination it is widely diffused.

Second in importance is the carbonate, calamine (q.v.) or zinc spar, which at one time was the principal ore; it almost invariably contains the carbonates of cadmium, iron, manganese, magnesium and calcium, and may be contaminated with clay, oxides of iron, galena and calcite; "white calamine" owes its colour to much clay; "red calamine" to admixed iron and manganese oxides.

Other zinc minerals are willemite, Zn 2 SiO 4, hydrozincite or zinc bloom, ZnCO 3.2Zn(OH)2, zincite or red zinc ore, ZnO, and franklinite, 3(Fe,Zn)0 (Fe,Mn) 2 0 3 .

Oxide of zinc, like most heavy metallic oxides, is easily reduced to the metallic state by heating it to redness with charcoal; pure red zinc ore may be treated directly; and the same might be done with pure calamine of any kind, because the carbon dioxide of the zinc carbonate goes off below redness and the silica of zinc silicate only retards, but does not prevent, the reducing action of the charcoal.

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.

As ores of zinc are usually shipped before smelting from widely separated places - Sweden, Spain, Algiers, Italy, Greece, Australia and the Rocky Mountains region of North America - it is important that they be separated from their mixtures at the mines.

The difficulty in separating zinc blende from iron pyrites is well known, and probably the most elaborate ore-dressing works ever built have been designed with this end in view.

Here very clean non-magnetic concentrate of willemite, which is an anhydrous zinc silicate and a very highgrade zinc ore, is separated from an intimate mixture of willemite, zincite and franklinites, with calcite and some manganese silicates.

The magnetic concentrates contain enough zinc to be well adapted to the manufacture of zinc oxide.

Neither mechanical nor magnetic concentration can effect much in the way of separation when, as in many complex ores, carbonates of iron, calcium and magnesium replace the isomorphous zinc carbonate, when some iron sulphide containing less sulphur than pyrites replaces zinc sulphide, and when gold and silver are contained in the zinc ore itself.

The ore, even if it is not blende, must be roasted or calcined 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 zinc sulphide passes in the first instance into sulphate, which demands a high temperature for its conversion into oxide.

For the desulphurization of zinc blende where it is not intended to collect and save the sulphur there are many mechanical kilns, generally classified as straight-line, horse-shoe, turret and shaft kilns; all of these may be made to do good work on moderately clean ores which do not melt at the temperature of desulphurization.

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.

After a time the flame becomes dazzling white, showing that zinc vapour is beginning to escape.

The iron adapters are now slipped on, 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 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."

Through an orifice in the outlet pipe (which is closed during the distillation by a loose plug) a hot iron rod can be introduced from time to time to clear away 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.

The distillate consists of a conglomerate of drops ("drop zinc").

When hydraulic pressure to the amount of 2000 to 3000 lb per square inch is applied, the saving is unquestioned, since less time is required to dry the pressed retort, its life in the furnaces is longer, its absorption of zinc is less, and the loss of zinc by passage through its walls in the form of vapour is reduced.

The men who charge and empty the retorts, those who draw and cast the metal, and those who keep the furnace in repair, need not know anything about the making or using of gas, and the men who make the gas need not know anything about a zinc furnace.

The specific effects of different impurities on the physical properties of zinc have only been imperfectly studied.

Fortunately, however, the small amounts of any of them that are likely to be found in commercial zinc are not for most purposes very deleterious.

Grades of commercial zinc are usually based on selected ores, and brands, when they mean anything, usually mean that the metal is made from certain ores.

Chemical control of the metal purchased is not nearly as common as it should be, and the refining of zinc is at best an imperfect operation.

To obtain the metal chemically pure a specially prepared pure oxide or salt of zinc is distilled.

A redistilled zinc, from an ordinarily pure commercial zinc, is often called chemically pure, but redistillation is seldom practised except for the recovery of zinc from galvanizer's dross and from the skimmings and bottoms of the melting furnaces of zinc rolling mills.

A bath, even of very impure zinc, is allowed to stand at about the temperature of the melting-point of the metal for forty-eight or more hours, whereupon the more easily oxidizable impurities can be largely removed in the dross at the top, the heavier metals such as lead and iron settling towards the bottom.

This method is rarely practised except by the rollers of zinc. A certain amount of refined zinc can be dipped from the furnace; a further amount, nearly free from iron, can be liquated out of the ingots cast from the bottom of the bath in a subsequent slow remelting, and it is sometimes possible to eliminate a zinciferous lead which collects in the sump of the furnace.

Owing to the fact that at temperatures between its melting and boiling point zinc has a strong affinity for iron, it is often contaminated by the scraper while being drawn from the condenser, as is shown by the fact that the scraper wears away rapidly.

Some brassfounders break from a single ingot the quantity of zinc required to produce the amount of brass they wish to compound in one crucible, but when perfect uniformity is desired the importance of remelting the zinc on a large scale cannot be too strongly emphasized.

The deposition of pure zinc is beset with many difficulties.

Zinc being more electro-positive even than nickel, all the heavy metals must be removed before its deposition is attempted.

Borchers, trace it to the presence of oxide, produced, for example, either by the use of a solution containing a trace of basic salt of zinc (to prevent which the bath should be kept just - almost imperceptibly - acid), or by the presence of a more electro-negative metal, which, being co-deposited, sets up local action at the expense of the zinc. Many processes have been patented, the ore being acted upon by acid, and the resulting solution treated, by either chemical or electrolytic means, for the successive removal of the other heavy metals.

The pure solution of zinc is then electrolysed.

Ashcroft patented a process of dealing with complex ores of the well-known Broken Hill type, containing sulphides of silver, lead and zinc, but the system was abandoned after a long trial on a practical scale.

Nahnsen's process, with an electrolyte containing alkali-metal sulphate and zinc sulphate, has been used in Germany, and a process invented by Dieffenbach has also been tried in that country.

Borchers and others deposit zinc from the fused chloride.

Properties Zinc is a bluish-white metal, showing a high lustre when freshly fractured.

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.

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 7.191 after rolling.

Compact zinc is bluish white; it does not tarnish much in the air.

If zinc be heated 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 (lana philosophica, " philosopher's wool").

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, copper or other more electro-positive metal be brought into contact with the zinc, it dissolves readily, with evolution of hydrogen and formation of the sulphate.

Cold dilute nitric acid dissolves zinc as nitrate, with evolution of nitrous oxide.

Zinc is also soluble in soda and potash solutions, but not in ammonia.

Zinc is largely used for "galvanizing" iron, sheets of clean iron being immersed in a bath of the molten metal and then removed, so that a coat of zinc remains on the iron, which is thereby protected from atmospheric corrosion.

Zinc forms only one oxide, ZnO, from which is derived a wellcharacterized series of salts.

It is chemically related to cadmium and mercury, the resemblance to cadmium being especially well marked; one distinction is that zinc is less basigenic. Zinc is capable of isomorphously replacing many of the bivalent metals - magnesium, manganese, iron, nickel, cobalt and cadmium.

Zinc oxide, ZnO, is maufactured for paint by two processes - directly from the ore mixed with coal by volatilization on a grate, as in the Wetherill oxide process, and by oxidizing the vapour given off by a boiling bath of zinc metal.

It is also manufactured by the latter process from the metallic zinc liquated out of galvanizer's dross.

Zinc hydroxide, Zn (OH) 2, is prepared as a gelatinous precipitate by adding a solution of any zinc salt to caustic potash.

At a boiling heat, zinc chloride dissolves in any proportion of water, and highly concentrated solutions, of course, boil at high temperatures; hence they afford a convenient medium for the maintenance of high temperatures.

Zinc chloride solution readily dissolves the oxide with the formation of oxychlorides, some of which are used as pigments, cements and for making artificial teeth.

Zinc bromide, ZnBr 2, and Zinc iodide, Zn12, are deliquescent solids formed by the direct union of their elements.

Zinc sulphide, ZnS, occurs in nature as blende (q.v.), and is artificially obtained as a white precipitate by passing sulphuretted hydrogen into a neutral solution of a zinc salt.

Zinc sulphate, ZnS04+7H20, or white vitriol, is prepared by dissolving the metal in dilute sulphuric acid.

If care be taken to keep the zinc in excess, the solution will be free from all foreign metals except iron and perhaps manganese.

A green pigment known as Rinmann's green is prepared by mixing I oo parts of zinc vitriol with 2.5 parts of cobalt nitrate and heating the mixture to redness, to produce a compound of the two oxides.

Zinc sulphate, like magnesium sulphate, unites with the sulphates of the potassium metals and of ammonium into crystalline double salts, ZnS04 R2S04-+-6H20, isomorphous with one another and the magnesium salts.

Zinc carbonate, ZnCO 3, occurs in nature as the mineral calamine (q.v.), but has never been prepared artificially, basic carbonates, ZnCO 3 .xZn(OH) 2, where x is variable, being obtained by precipitating a solution of the sulphate or chloride with sodium carbonate.

To obtain a product free of Cl or S04, there must be an excess of alkali and the zinc salt must be poured into the hot solution of the carbonate.

Of zinc phosphates we notice the minerals hopeite, Zn.

Zinc may be quantitatively estimated by precipitating as basic carbonate, which is dried and ignited to zinc oxide.

Pharmacology And Therapeutics Of Zinc Compounds Zinc chloride is a powerful caustic, and is prepared with plaster of Paris in the form of sticks for destroying warts, &c. Its use for this purpose at the present day is, however, very rare, the knife or galvanocautery being preferred in most cases.

Numerous other salts of zinc, used in medicine, are of value as containing this metal.

Lotio Rubra, the familiar "Red Lotion," a solution of zinc sulphate, is widely used in many catarrhal inflammations, as of the ear, urethra, conjunctiva, &c. There are also innumerable ointments.

It may be prepared by fusion of ortho-toluene sulphonic acid with potash; by the action of phosphorus pentoxide on carvacrol; or by the action of zinc chloride on camphor.

Lead, zinc and other metals have also been reduced in this manner.

Anthracene has also been obtained by heating ortho-tolylphenyl ketone with zinc dust C6H4(CH CH =H20+C6H4 I)C6H4.

At a red heat rutile is produced, at the boiling point of zinc brookite, and of cadmium anatase.

Wallach, Ber., 1881, 14, P. 421); by the action of reducing agents on nitroparaffins; by the action of zinc and hydrochloric acid on aldehyde ammonias (German Patent 73,812); by the reduction of the phenylhydrazones and oximes of aldehydes and ketones with sodium amalgam in the presence of alcohol and sodium acetate (J.

Tafel, Ber., 1886, 19, p. 1924), by distilling the amido-acids with lime, by heating phenols with zinc chloride ammonia (V.

The secondary amines may be of two types-namely,the purely aromatic amines, and the mixed secondary amines, which contain an aromatic residue and an alkyl group. The purely aromatic amines result upon heating the primary amines with their hydrochlorides, and, in some cases, by heating a phenol with a primary amine and anhydrous zinc chloride.

When heated with monobasic saturated acids and zinc chloride it yields acridines.

The principal exports are olive oil, wheat, esparto grass, barley, sponges, dates, fish (especially tunny), hides, horses, wool, phosphates, copper, zinc and lead.

Within these limits are to be found most of the minerals known - gold, silver, quicksilver, copper, lead, zinc, iron, manganese, wolfram, bismuth, thorium, vanadium; mica, coal, &c. On or near the coast are coal, salt, sulphur, borax, nitrates and petroleum.

Practically any vessel may serve as a receiver - test tube, flask, beaker, &c. If noxious vapours come over, it is necessary to have an air-tight connexion between the condenser and receiver, and to pro vide the latter with an outlet tube leading to an absorption column or other contrivance in which the vapours are taken up. If the substances operated upon decompose when heated in air, as, for example, the zinc alkyls which inflame, the air within the apparatus is replaced by some inert gas, e.g.

Lead is of frequent occurrence, and indeed the area through which copper, silver, lead, tin and zinc are distributed in sufficient quantities to make mining answer, comprises at least 80,000 sq.

There are also present small quantities of arsenic and antimony, and zinc is found generally as a mere trace, but sometimes reaching to 6%.

Copper, tin, lead and zinc, mixed in various proportions by different experts, are the ingredients, and the beautiful golden hues and glossy texture of the surface are obtained by patina-producing processes, in which branch of metal-work the Japanese show altogether unique skill.

The mineral wealth of Baden is not great; but iron, coal, zinc and lead of excellent quality are produced, and silver, copper, gold, cobalt, vitriol and sulphur are obtained in small quantities.

Its other mineral resources include graphite, copper, zinc, lead, salt, alum, potter's clay, marble and good mill and building stones.

Hermite, which consisted in the production of bleach-liquors by the electrolysis (according to the 1st edition of the 1884 patent) of magnesium or calcium chloride between platinum anodes carried in wooden frames, and zinc cathodes.

Rotating zinc cathodes were used, with scrapers to prevent the accumulation of a layer of insoluble magnesium compounds, which would otherwise increase the electrical resistance beyond reasonable limits.

On treatment with zinc and alkyl iodides or with zinc alkyls they are converted into esters of hydroxy-dialkyl acetic acids.

If we melt copper and add to it about 30% of zinc, or 20 of tin, we obtain uniform liquids which when solidified are the well-known substances brass and bell-metal.

For example, if vapours of the volatile metals cadmium, zinc and magnesium are allowed to act on platinum or palladium, alloys are produced.

Fromm have shown that alloys may be precipitated from dilute solutions by zinc, cadmium, tin, lead and copper.

Thus a strip of zinc plunged into a solution of silver sulphate, containing not more than 0.03 gramme of silver in the litre, becomes covered with a flocculent precipitate which is a true alloy of silver and zinc, and in the same way, when copper is precipitated from its sulphate by zinc, the alloy formed is brass.

A very similar fact, that brass may be formed by electrodeposition from a solution containing zinc and copper, has long been known.

The presence of minute quantities of cadmium, lead, bismuth, antimony, arsenic, tin, tellurium and zinc renders gold brittle, 2 ' 0 15th part of one of the three metals first named being sufficient to produce that quality.

Magnetic pyrites, copper pyrites, zinc blende and arsenical pyrites are other and less important examples, the last constituting the gold ore formerly worked in Silesia.

They may be said to possess a series of bronzes, in which gold and silver replace tin and zinc, all these alloys being characterized by patina having a wonderful range of tint.

Gold and Zinc.-When present in small quantities zinc renders gold TABLE II.-Gold brittle, but it may be added to gold in larger quantities without destroying the ductility of the precious metal; Peligot proved that a triple alloy of gold, copper and zinc, which contains 5.8% of the lastnamed, is perfectly ductile.

The alloy of II parts gold and i part of zinc is, however, stated to be brittle.

The strengths employed depend also upon the mode of precipitation adopted, stronger solutions (up to 0.25% KCN) being used when zinc is the precipitant.

In the Transvaal the operation occupies 32 to 4 days for fine sands, and up to 14 days for coarse sands; the quantity of cyanide per ton of tailings varies from 0.26 to 0.28 lb, for electrolytic precipitation, and o 5 lb for zinc precipitation.

The precipitation is effected by zinc in the form of bright turnings, or coated with lead, or by electrolysis.

It may be noticed that the potassium zinc cyanide is useless in gold extraction, for it neither dissolves gold nor can potassium cyanide be regenerated from it.

In the wider compartments are placed sieves having sixteen holes to the square inch and bearing zinc turnings.

The slime is cleaned out fortnightly or monthly, the zinc turnings being cleaned by rubbing and the supernatant liquor allowed to settle in the precipitating boxes or in separate vessels.

The slime so obtained consists of finely divided gold and silver (5-5 0%), zinc (30-60%), lead (io%), carbon (io%), together with tin, copper, antimony, arsenic and other impurities of the zinc and ores.

This dissolves out the zinc. Lime is added to bring down the gold, and the sediment, after washing and drying, is fused in graphite crucibles.

Its advantages over the zinc process are that the deposited gold is purer and more readily extracted, and that weaker solutions can be employed, thereby effecting an economy in cyanide.

The Carpathian system is richer in metallic ores than any other mountain system of Europe, and contains large quantities of gold, silver, copper, iron, lead, coal, petroleum, salt, zinc, &c., besides a great variety of useful mineral.

It is precipitated as the metal from solutions of its salts by the metals of the alkalis and alkaline earths, zinc, iron, copper, &c. In its chemical affinities it resembles arsenic and antimony; an important distinction is that it forms no hydrogen compound analogous to arsine and stibine.

The metal can be reduced by magnesium, zinc, cadmium, iron, tin, copper and substances like hypophosphorous acid from acid solutions or from alkaline ones by formaldehyde.

Tin amalgam is used for "silvering" mirrors, gold and silver amalgam in gilding and silvering, cadmium and copper amalgam in dentistry, and an amalgam of zinc and tin for the rubbers of electrical machines; the zinc plates of electric batteries are amalgamated in order to reduce polarization.

Lead and zinc are mined in much smaller quantities, alum and sulphur are also.

It imports general merchandise and manufactures, and exports phosphates, iron, zinc, barley, sheep, wool, cork, esparto, &c. There are manufactories of native garments, tapestry and leather.

Many of the elements such as copper, lead, zinc, nickel, cobalt and manganese have only been found in the substance of sea-weeds and corals.

It combines with many metallic sulphates (silver, zinc, cobalt, nickel, &c.) to form double sulphates of the type Cs2S04 RS04.6H20.

Mourlot has shown that aluminium sulphide, zinc sulphide and cadmium sulphide are the only sulphur compounds which can resist the heat of the electric furnace without decomposition or volatilization, and of these aluminium sulphide is the only one which is decomposed by water with the evolution of sulphuretted hydrogen.

Other minerals found in small quantities are copper, lead, zinc, iron ores, manganese ores and tin.

The first mines to be worked in Iowa were those for lead and zinc at Dubuque and to the northward.

These are little mined at present, only 110 tons of lead ore and 516 tons of zinc ore being taken from the mines in 1908.

It behaves more as a ketone than as a quinone, since with hydroxylamine it yields an oxime, and on reduction with zinc dust and caustic soda it yields a secondary alcohol, whilst it cannot be reduced by means of sulphurous acid.

It may be prepared from osmiridium by fusing the alloy with zinc, the zinc being afterwards removed by distillation.

As an alternative the osmiridium is fused with zinc, the regulus treated with hydrochloric acid, and then heated with barium nitrate and barium peroxide.

The tetroxide, 0s04, can be easily reduced to the metal by dissolving it in hydrochloric acid and adding zinc, mercury, or an alkaline formate to the liquid, or by passing its vapour, mixed with carbon dioxide and monoxide, through a red-hot porcelain tube.

The best metals for coinage are gold, silver, platinum, copper, tin, nickel, aluminium, zinc, iron, and their alloys; certain alloys of gold, silver, copper and nickel have the best combination of the required qualities.

Silver bullion, and the copper, tin and zinc required to make up bronze, are bought by the Mint and manufactured into coin, which is kept in stock and issued as it may be required.

Coinage bronze consists of copper 95 parts, tin 4 parts and zinc I part, and a ton yields X44 8 in pence or £ 373, 6s.

It is the centre of the mining district of Upper Silesia, and its population is mainly engaged in such operations and in iron and zinc smelting.

There are many other valuable ores - copper, iron, lead, zinc, antimony, chrome and manganese.

A small quantity of zinc (7 tons in 1906) is occasionally produced.

Copper, zinc and bismuth are also worked.

The manufacture of iron and steel goods is carried on; other industries include the manufacture of zinc wares, tanning, distilling and brewing.

Bernburg is the seat of considerable industry, manufacturing machinery and boilers, sugar, pottery and chemicals, and has lead and zinc smelting.

The Edison electric meter, like those of Sprague and Lane-Fox, was based upon the principle that when an electric current flows through an electrolyte, such as sulphate of copper or sulphate of zinc, the electrodes being plates of copper or zinc, metal is dissolved off one plate (the anode) and deposited on the other plate (the cathode).

Before being placed in the cells the zinc plates were weighed.

The shunted voltameter was then inserted in series with the electric supply mains leading to the house or building taking electric energy, and the current which passed dissolved the zinc from one plate and deposited it upon the other, so that after a certain interval of time had elapsed the altered weight of the plates enabled the quantity of electricity to be determined from the known fact that an electric current of one ampere, flowing for one hour, removes 1.2533 grammes of zinc from a solution of sulphate of zinc. Hence the quantity in amperehours passing through the electrolytic cell being known and the fraction of the whole quantity taken by the cell being known, the quantity supplied to the house was determined.

Owing to the cost and trouble of weighing a large number of zinc plates, this type of meter fell into disuse.

The minerals of Siam include gold, silver, rubies, sapphires, tin, copper, iron, zinc and coal.

A freshly prepared surface of the metal closely resembles zinc in appearance, but on exposure to the air it rapidly tarnishes, becoming yellowish and ultimately grey or white in colour owing to the formation of a surface layer of calcium hydrate.

At first a trade was carried on in wine, colonial wares, alcoholic liquors and salt; there are now manufactures of earthenware, glass and crystal, arms, paper, woollens, tools, lead, copper and zinc work, as well as breweries, and tobacco and cigar factories, and a trade in corn and butter.

Such was the case not only with some metals, such as lead, zinc, copper, but still more strikingly with textile materials such as wool, flax, and the like, and most of all with agricultural products such as grain, meat and meat products, timber.

Copper, silver, lead, and zinc are found in considerable quantities, and as regards quicksilver, Kwei-chow is probably the richest country in the world.

The olefines may be synthetically prepared by eliminating water from the alcohols of the general formula CnH2n+1 OH, using sulphuric acid or zinc chloride generally as the dehydrating agent, although phosphorus pentoxide, syrupy phosphoric acid and anhydrous oxalic acid may frequently be substituted.

The higher members of the series readily polymerize in the presence of dilute sulphuric acid, zinc chloride, &c. For the first member of the series see Ethylene.

It may be prepared by passing carbon dioxide over red-hot carbon, or red-hot iron; by heating carbonates (magnesite, chalk, &c.) with zinc dust or iron; or by heating many metallic oxides with carbon.

Algeria is rich in minerals, found chiefly in the department of Constantine, where iron, lead and zinc, copper, calamine, antimony and mercury mines are worked.

The most productive are those of iron and zinc. Lignite is found in the department of Algiers and petroleum in that of Oran.

The chief exports are sheep and oxen, most of which are raised in Morocco and Tunisia, and horses; animal products, such as wool and skins; wine, cereals (rye, barley, oats), vegetables, fruits (chiefly figs and grapes for the table) and seeds, esparto grass, oils and vegetable extracts (chiefly olive oil), iron ore, zinc, natural phosphates, timber, cork, crin vegetal and tobacco.

In the case of the Clark standard cell above mentioned the elements are mercury and zinc separated by a paste of mercurous sulphate mixed with a saturated solution of zinc sulphate.

In the Weston standard cell cadmium and cadmium sulphate are substituted for zinc and zinc sulphate; it has the advantage of a much smaller coefficient of temperature variation than the Clark cell.

The legs are filled with solutions of zinc sulphate and copper sulphate, the zinc rod being in the zinc sulphate and the copper rod in the copper sulphate.

The solutions are made by dissolving the purest recrystallized sulphate of copper and sulphate of zinc in distilled water.

For the zinc solution, take 55.5 parts by weight of crystals of zinc sulphate (ZnS0470H2) and dissolve in 44.5 p arts by weight of distilled water; the resulting FIG.

The manufactures are insignificant; and although silver, copper, iron, zinc, lead and marble are said to exist in considerable quantities, the only ores that have been worked are gold, silver and copper.

Lead and zinc are mined in small quantities near Marion in Crittenden county and elsewhere in connexion with mining for fluorspar; in 1907 the output was 75 tons of lead valued at $7950 and 358 tons of zinc valued at $4 2, 2 44.

It can be prepared by the reduction of phenyl propiolic acid with zinc and acetic acid, by heating benzal malonic acid, by the condensation of ethyl acetate with benzaldehyde in the presence of sodium ethylate or by the so-called "Perkin reaction"; the latter being the method commonly employed.

After coal and iron the most valuable minerals are zinc, lead, pyrites and copper.

The sulphocyanide is converted into the potassium salt by adding potassium sulphate, and finally desulphurized by lead, zinc, or iron.

It can be estimated quantitatively by mixing a dilute solution with potassium iodide and hydrochloric acid in excess, adding excess of zinc sulphate, neutralizing the excess of free acid with sodium bicarbonate, and determining the amount of free iodine by a standard solution of sodium thiosulphate.

In the neighbourhood of Cracow there are mines of coal and zinc, and not far away lies the village of Krzeszowice with sulphur baths.

So also do the lead and zinc of south-western Wisconsin and the adjacent parts of Iowa and Illinois.

The zinc and lead of the Joplin district of Missouri are in the limestone of this system, and the corresponding limestone in some parts of Colorado, as at Leadville, is one of the horizons of rich ore.

The extent and value of the deposits of zinc ore in the Saucon Valley, Pennsylvania, had also just become known in 1850.

According to the bureau of the census the value in 1902 of the lead yielded by copper, by non-argentiferous lead and zinc, and by gold and silver ores respectively was $19,053, $5,850,721 and $12,311,239.

According to the census data for 1889 and 1902 there was an in Zinc crease in value of product of 184.1% in the interval, and of 109.5% in the quantity of ore produced.

The value of products in 1902 were reported as $340,686 from gold and silver ores, and $8,665,675 from non-argentiferous lead and zinc ores.

The total product of zinc from domestic ore for the entire country was 7343 short tons in 1873, passed 100,000 tons in 1898, and 200,000 in 1907, when it amouiited to 223,745 tons.

Summing up the economic features of the Cordilleran belt, it includes many of the best coal-mines and the most extensive deposits of gold, copper, lead and zinc of the Dominion, while in silver, nickel and iron Ontario takes the lead.

Epsom salts crystallizes in the orthorhombic system, being isomorphous with the corresponding zinc and nickel sulphates, and also with magnesium chromate.

Wohler reduced the sesquioxide by zinc, and obtained a shining green powder of specific gravity 6.81, which tarnished in air and dissolved in hydrochloric acid and warm dilute sulphuric acid, but was unacted upon by concentrated nitric acid.

The principal industries are the smelting of zinc and the manufacture of cement, rolled zinc, bricks, sulphuric acid and clocks; in 1905 the city's factory products were valued at $3,158,173.

They may be prepared by the reduction of nitro compounds in alkaline solution (using zinc dust and alkali, or a solution of an alkaline stannite as a reducing agent); by oxidation of hydrazo compounds; or by the coupling of a diazotized amine and any compound of a phenolic or aminic type, provided that there is a free para position in the amine or phenol.

Mitscherlich in 1834, may be prepared by reducing nitrobenzene in alcoholic solution with zinc dust and caustic soda; by the condensation of nitrosobenzene with aniline in hot glacial acetic acid solution; or by the oxidation of aniline with sodium hypobromite.

In the vicinity there are valuable lead, zinc and coal mines, and quarries of Carthage "marble," with which the county court house is built.

The spectra of magnesium, calcium, zinc, cadmium and mercury, give the two branch series, and each series is repeated three times with constant difference of frequency.

Heated with anhydrous sodium acetate and acetic anhydride it gives cinnamic acid; with ethyl bromide and sodium it forms triphenyl-carbinol (C 6 H 5) 3 C OH; with dimethylaniline and anhydrous zinc chloride it forms leuco-malachite green C6H5CH[C6H4N(CH3)2]2; and with dimethylaniline and concentrated hydrochloric acid it gives dimethylaminobenzhydrol, C 6 H 5 CH(OH)C 6 H 4 N(CH 3) 2.

It may also be prepared by heating a mixture of carbon, oxide of iron and magnesite to bright redness; and by heating a mixture of magnesium ferrocyanide and sodium carbonate, the double cyanide formed being then decomposed by heating it with metallic zinc. Electrolytic methods have entirely superseded the older methods.

Further he prepared a large number of substances, including the chlorides and other salts of lead, tin, iron, zinc, copper, antimony and arsenic, and he even noted some of the phenomena of double decomposition.

The first experiment which he has recorded was the construction of a voltaic pile with seven halfpence, seven disks of sheet zinc, and six pieces of paper moistened with salt water.

The deposits of zinc in the vicinity of Beuthen are perhaps the richest in the world, and produce twothirds of the zinc ore of Germany (609.000 tons).

Blue or Roman vitriol ' is copper sulphate; green vitriol, ferrous sulphate (copperas); white vitriol, zinc sulphate; and vitriol of Mars is a basic iron sulphate.

Both schemes appeared practically impossible; potassium cost about L 1 7 per lb, gave a very small yield and was dangerous to manipulate, while on the other hand, the only source of electric current then available was the primary battery, and zinc as a store of industrial energy was utterly out of the question.

An absolutely clean surface becomes tarnished in damp air, an almost invisible coating of oxide being produced, just as happens with zinc; but this film is very permanent and prevents further attack.

For stove and greenhouse plants, orchids, ferns, &c., labels made of xylonite, zinc and other materials are also used.

After boiling about an hour, it is allowed to cool, the water is drawn off, and the oil is transferred to zinc tanks or clarifiers capable of holding from 60 to loo gallons.

It consists, indeed, mainly of iron-pyrites, with a notable but variable proportion of copper, sometimes with silver and gold, and not infrequently associated with lead and zinc sulphides.

Within the Carboniferous rocks, but due to the action of various agencies long after their deposition, are important ore formations; such are the Rio Tinto ores of Spain, the lead and zinc ores and some haematite of the Pennine and Mendip hills and other British localities, and many ore regions in the United States.

Zinc dust and alcoholic acetic acid reduce it to aniline and phenylhydrazine.

In preparing the gas by the action of metals on acids, dilute sulphuric or hydrochloric acid is taken, and the metals commonly used are zinc or iron.

When prepared by the action of metals on bases, zinc or aluminium and caustic soda or caustic potash are used.

Hydrogen may also be obtained by the action of zinc on ammonium salts (the nitrate excepted) (Lorin, Comptes rendus, 1865, 60, p. 745) and by heating the alkali formates or oxalates with caustic potash or soda, Na2C204+2NaOH = H 2 +2Na 2 CO 3.

Dixon); by passing air through solutions of strong bases in the presence of such metals as do not react with the bases to liberate hydrogen; by shaking zinc amalgam with alcoholic sulphuric acid and air (M.

Traube, Ber., 1882, 15, p. 659); in the oxidation of zinc, lead and copper in presence of water, and in the electrolysis of sulphuric acid of such strength that it contains two molecules of water to one molecule of sulphuric acid (M.

Iron ore is found in abundance near Coblenz, the Bleiberg in the Eifel possesses an apparently inexhaustible supply of lead, and zinc is found near Cologne and Aix-la-Chapelle.

Zinc, lead and copper are also extensively worked in the Palaeozoic rocks of the Ardennes.

Other minerals are iron, manganese, lead and zinc. The iron mines produce much less than formerly, and the want of iron is a grave defect in Belgian prosperity, as about £5,000,eoo sterling worth of iron has to be imported annually, chiefly from French Lorraine.

The yield of lignite is less than 100,000 tons annually; of zinc 10,000 to 12,000 tons; of copper and lead small.

Characteristic, also, is their action on a photographic plate, and the phosphorescence which they occasion when they impinge on zinc sulphide and some other salts.

The minerals found in the department include the coal of the basins of Aubin and Rodez as well as iron, zinc and lead.

The substance is usually optically isotropic, though sometimes it exhibits anomalous double refraction; fibrous zinc sulphide which is doubly refracting is to be referred to the hexagonal FIG.

The mineral is also frequently found massive, with a coarse or fine granular structure and a crystalline fracture; sometimes it occurs as a soft, white, amorphous deposit resembling artificially precipitated zinc sulphide.

Black blende containing ferrous sulphide, in amounts up to 15 or 20% isomorphously replacing zinc sulphide, is known as marmatite (from Marmato near Guayabal in Colombia, South America) and christophite (from St Christophe mine at Breitenbrunn near Eibenstock in Saxony).

Blende occurs in metalliferous veins, often in association with galena, also with chalcopyrite, barytes, fluorspar, &c. In oredeposits containing both lead and zinc, such as those filling cavities in the limestones of the north of England and of Missouri, the galena is usually found in the upper part of the deposit, the blende not being reached until the deeper parts are worked.

In these cases the zinc sulphide has probably arisen from the reduction of sulphate by organic matter.

The hydroxide Be(OH)2 separates as a white bulky precipitate on adding a solution of an alkaline hydroxide to a soluble beryllium salt; and like those of aluminium and zinc, this hydroxide is soluble in excess of the alkaline hydroxide, but is reprecipitated on prolonged boiling.

About 90% of the zinc produced in Europe is yielded by Belgium and Germany.