Volume 14 (1867) (436 pages)

The Mining antl Scientific Dress, Communications. In THIS NRPARTMENT we invite the FRRE Discussion of all roper subjeets—correspondciits alone being responsible for he ideas and theories they advance. iWritten for the Mining and Setentific Press.] Progress of Metallurgy and Saving of Fuel. Messrs. Hnrrors.—It seems strange that with the abundance of ore we have in our mines, and the qnantity of fuel at our command, we are still obliged to send oves abroad for reduction, and afterward buy the metals at snch prices as the sméliers may choose to place uponthem. Itmustseem to outside observers that we neither possess the ores or fuel, so often mentioned in your valnable paper, or that we laek the knowledge of extracting the metals from the ores. Yet the fact is, we have both ores and talent in abundance ; and having in our favor the expeusive transport of ore to Europe aud the metal back again, we surely onght to compete suecessfully with the foreign manufacturers, not ouly in gold, silver and copper ores, but in ironaswell. If metallurgy had made no progress, and we had to resort to old modes of smelting, we still eould retain the field; but if we take into consideration the improvements made in the saving of fuel by various inventions, foremostamong which stands C. W. Siemeu’s, we shall find that we possess all wo need in our midst if we ouly take advantage thereof. Various experiments have been mace in the way of smelting works in California, and as far as gold and silver ore is concerued, I believe I was the owner of the only successful works ever erected in this State. For copper ores various experiments have been made with very poor success. The parties engaged in those experiments here had some theoretical, but not the practical knowledge necessary to make the proper calculation for desired results ; for if it had been otherwise, and they had formed a full knowledge of the . fuel and ore which they expected to mauipulate, they would not have speut their friends’ money in vain, and destroyed all, confidence in further euterprise. The impression has goue out that, as the Antioch smelting works were a failure, Mount Diablo coal is not fit for smelting ores. To this I respectfully dissent by saying it makes but little difference with regard to the character of the coal, whether it he anthracite, bituminous, lignite, or eveu wood, peat or sawdust; any material containing hydro-caxbon may be employed to raise as high a degree of heat as is necessary to smelt any metal or ore. Ali that is necessary is the proper Imowledge of the fuel and its apphecation ; with that we need never fail to produce the degree of heat requisite to effect the reduction of the ores of metals. Few of our mineralogisis have given this subject the proper attention it deserves ; but men of the greatest ability, like Professor Faraday, haye greatly ventilated the subject. I will give you a short abstract of what he has said on the subject of fuel, in connection with gas regenerating furnaces : ‘Gaseous fuel is obtained by the mutual action of coal, air and water, at a moderate ved heat, A brick chamber, perhaps six feet by twelve, and about ten feet high, is constructed with one of its end walls converted into a fire grate, 7. ¢., about half way down it is a solid plate, and for the rest of the distance consists of strong horizoutal plate bars, where air enters, the whole being at an inclination, such as that which the side of a heap of coals wonld naturally take. Coals are poured through openings above, upon this combination wall and grate, and being fired at the under surface, they burn at the place where the air enters ; but asthe layer of coal is from two to three feet thick, various operations go on in those parts of the fuel which cannot burn, for want of aiz. “Thus the upper and cooler part of the coal produces a large body of hydro-carbons ; the cinders or coke which are not volatilized, approach, in descending, towards the grate; that part which is nearest the grate burns, with the entering air, into carbonic acid, and the heat evolved ignites the mass above it. The carbonic acid passes slowly through the ignited carbon, becomes converted into carbonie oxyd, and mingles in the upper part of the chamber (or gas producer) with the former hydrdé-carbons. The water, which is purposely introduced at the bottom of the arrangement, is first vaporized by the heat and theu decomposed by the ignited fnel, and re-arranged as hydrogen aud carbonic oxyd; and only the ashes of the coal are removed, as solid matter from the chamber at the bottom of the fire bars. ‘These mixed gases form the gaseous fuel, The nitrogen which enters with the air at the grate, is mingled with them, constituting about one-third of the whole volume. The gas vises up a large vertical tube, from twelve to fifteen feet, after which it proceeds horizontally for any required distance, and then desceuds to the heat regenerator, throngh which it passes before it enters the furnaces. “A yegenerator is a chamber packed with fire bricks, separated so as to allow of the free passage of air or gas between them. There are geuerally four of them placed uuder a furnace. The gas ascends through one of these ehambers while air ascends through the neighboring ehamber, and both are conducted through one end of the furnace where, mingled, they burn, produciug the heat due to their chemieal action. Passing onward to the other end of the furnace, they (the combined gases) find precisely similar outlets down which they pass ; and traversing the two remaining regenerators from above downwards, heat them intensely, especially the upper part; and so travel ou in their cooled state to the chimney. ‘Now the passages between the four regenerators and the gas aud air are supplied with yalves aud deflecting plates, which are like four way cocks in their action ; so that by the use of a lever these regulators admit air or gas to the furnace. “Tt is to be observed that the intensity of the heated flame, which leaves the furnace for the stack, always proceeds downwards through the regeuerators ; so that the upper part thereof is most intensely ignited, keeping back, as it does, the inteuse heat. So effectually is this accomplished, that the gases which enter the stack to be cast into the air, are not heated above three hundred degrees of Fahrenheit. “Tt is cousidered that when the furnace is in full order, the heat carried forward to be evolved by the chemical action of combustion is aboutfour thousand degrees, whilst that carried back by the regenerator is about three thousand degrees; making an intensity of power which, unless moderated, would fuse furnace and all else exposed to its action. “Thus the regeuerators are alternately heated and cooled by the outgoing aud cutering gases and air. “Great facility is afforded in the management of a gas fuynace. Not merely can the supply of gas and air to the furuace be goyerned by valvesin the passages, but the very manufacture of the gas fuel itself can be diminished, or eveu stopped, by cutting off the supply of air to the grate of the gas producer ; and this is important, inasmuch as there is no gasometer required. “‘The economy in fuel is estimated practically as oue-half, even wheu the cheapest kind of fuel is used. Carbon, when burnt perfectly into carbonic acid, in a gas producer, evolves about four thousaud degrees of heat; but if burnt into carbonic oxyd, it only evolves twelve hundred degrees. The carbonic oxyd, in its fuel form, carries ou with it the twenty-eight hundred degrees in chemical force which it evolves when burning in the real furnace, with a suflicient supply of air. “The remaining twelve hundred degrees are employed in the gas producer, in distilling hydro-carbons, decomposing water, ete. . The whole mixed gaseous fnel cau evolve about four thousand degrees in the furnace, . to which the regenerator can return about) three thousand more.” In addition to the above, I can produce other statements, from more than fifty establishments where gas furnaces are used, and where a saving of more than 50 per cent. of fuel is effected. IT have not only seeu, but built and worked such furnaces ; and if our people would adopt them for metallurgical operations, we should not be obliged to send any more ore to a foreign country for reductiou. In my next I will give you a description of the application of petrolenm and coal tar for heating boilers, smelting and glass furnaces. J. Mosuemer. An Avanancaz.—A gang of Chiuamen at work on the Central Pacific Railroad, were buried by asnow-shde on the 22d December. Some four or five were dead when exhumed. The snow is from ten to fifteeu feet deep on the Summit. (Written for the Mining and Seicntifie Press.) PROCESS OF ROASTING ORES, ETO, Translated from the Germau of F. Plattner, for the Mining aud Gas-Light Jonrnal, New York. — ‘ BY J. H. TIEMANN, M. E. Numner Five. 8. Matt.—This mill product consists chiefly of F.25, Fe S in different proportions, so that either the F,?5 is in larger proportions than tho F, 8, or—which less frequently occurs—that the Fe § is in larger proportions than the Fe2S. Iu the former case we may suppose the matt composed of x(Fo 2S, Fo S)4+4(Fe 2S, Fe S) and in the latter case a8 x (Fe 2S, Fe S)+(Fe 28, nFo S), in which case, however, a small part of the protosulphide and subsulphide is sometimes replaced by other metals, as snbsulphide of copper, sulphides of lead, zinc, Manganese and silver; the matt also often contains slag mechanically combined, which, in a furnace matt containing sulphide of zine, and consequently difficulily fusible, may often amount to twenty per cent. When,ores consisting chicfly of pyrites, partly in a natural and partly in a roasted state, are smelted to a matt in a furnacc, under a covering of slag, the sesquoxyd of iron in the roasted part is reduced, ut the expense of the sulphur of the raw part which escapes as a vapor to a protoxyd, and combines as such with the earthy materials forming a slag, which afterwards combines with the slag used as a covering.* When the slaging (fluxing) is imperfect, wbich occurs when there is a lack of earthy material, particularly quartz, a part of the protoxyd of iron may be taken np by the matt, an oxysulphuret may be formed (™Fo25+I, O) and a matt may be formed haying the fermula, Fo? S+nyFe (8, O). If the ore was not free from other metals, which are likewise inclined to separate as sulphurets, they will be included in the compound. Pulverized matt, when roasted, acts similar to magnetic pyrites. If it be roasted at a low temperature and with proper precautions at first, besides free sequoxyd of iron, considerable quantities of protosulphate is formed, which, afterwards, a, an increased temperature, as in the case of that formed from mugnetie pyrites, is changed to persulphate under evolution of sulphurous acid; the anount fermed is abeut twenty-ono per cent., having seven per ccnt. of sulphuric acid. 4. Kupferkies (copper pyrites) Cu? S, Fo? S38 when roasted, acts similar to magnetie pyrites, except that besides a small quantity of persulphate of iron, a sulphato and free oxyd of copper is formed, If coarsely pulverized, copper pyrites be roasted at a dark-red heat and constantly stirred, and atmospheric air admitted until the smell of sulphurous acid disappears, it changes to a spongy powder, which, when cooling, chauges to a dark red color. This powder consists chiefly of sesquoxyd of iron, a suboxyd and protoxyd of copper, and contains protosulphate and persulphate of iron, and sulphate of copper—the latter in considerable quantities. If this product be now submitted to a bright red heat, and air admitted, the protesulphate of iron (as in the case of pyrites and magnetie pyrites) changes to persulphate; and there remains, besides the sesquoxyd of iron and the protoxyd of copper, only sulphate of copper and a little persulphate of iron with twenty per cent. of sulphurie acid. If the temperatnre be still increased, thcso sulphates are decomposed, leaving the free oxyds of iren and copper, the sulphuric aeid escaping partly as such, and partly as sulplmrous acid and oxygen. ~ 5. Kupferstein’ (copper matt). This mill product, when containing a high percentage of copper, consists principally of mCu 25, Fe S; when centaining a medium pereentage of copper Cz 8, Fe 2 8; and when having a low percentage, m(Cu? 8, F,2S)+Fe §, or in the latter ease is a mixture of eopper matt mCu2S, Fe S, witb iron matt Fe 2 8, F, §, in variable proportions, so that a eopper matt, with a very low pereentago of copptr, may have tbe composition (Cy 28, Fo 25)+Fe S$). The copper matt sometimes contains other sulpur metals, as lead, zine, manganese and silver, which replace one another; and is not always free from a mixtnro of sulphide of antimony or arsenic, which unito with the disulphide of copper, and pass jnto the matt. When pulverized copper matt is exposed to a dark red heat, and air admitted, it glows readily in consequence of the oxydation of its components ; at first it is converted into suboxyd of copper, sesquoxyd and protosnlpbate of iron, sulphurous aeid * When a part of the sesquoxyd has been reiuced only to magnetic oxyd (sesquoxyd plus protoxyd), and is present in any quantity, 1t crystallizes in beautiful glistening octahedrons, if the slag, iu a Jarge mass, be allowed to cool j slowly. passing off; but after the sulphides, being kept constantly stirred, have heen mostly oxydized, and the temperature increased decomposing the protosulphate of iron, it is converted into free oxyd of copper and sesquosyd of iron, with sulphate of copper and persulphate of iron, having abont eighteen per cent. of sulphnric acid; by continued roasting and constant stirring, tbe sulphates of copper and iron—the fermer only at a bright red heat—are decomposed, leaving free oxyds, while sulphurous acid, oxygen and sulphurie acid pass off—the latter in tho form of white vapors. 6, Bleiglanz (sulphide of lead) Pp S, when pulyerized and exposed to a dark red: beat, air being admitted, glows of itself in consequence of the ox_ ydation, evolves sulphurons acid, and at a continned dark red beat is converted into sulphate and free oxyd of lead. A higher temperature, not sufficient, however, to cause a sintering or smelting of tho free oxyd, produces no further ebange, for tho reason that the sulphate formed during the roasting eannot he decomposed and cenverted into fico oxyd. As the proportion between the snlphate and free oxyd varies in proportion to the amonnt of other metals present, this portion_of our snbject will he treated more fully further on, when wo come to explain the chemical changes which take place in the roasting of sulphur metals. 7, Wismnthglang (sulphurct of bismuth) B; 2 83, In a powder, when beated on a clay saucer ina muffel, just to redness, air being admitted, clows of itself, evolves sulphurous acid, and is very soon conyerted into a light grey powder without sintering (caking). This powder cousists of an oxyd and sulphate of hismuth. If the substanée contained copper pyrites, the product when cool has a dark yellowish green color. If this be heated in a glass tube to a bright red, it smelts, with the evolution of 2 little sulphurie acid, to a light brownish grey mass, which on the edges is translucent. 8. Zinkblond (sulphuret of zinc), yellow and brown, Zy S and Black F, S+3Z» §, is, of all sulphur metals whieb require to be treated by fire, the most difficult to roast. Even when in a fine pewder, it requircs an uninterupted red heat and strong draught of air for its complete oxydation, under whicb circumstances sulphurous acid is evolved, while free oxyd and more or less sulphate of zinc (nentral and hasic) is formed. If the blend contains irou sulphuret, cither as a component (blackjack) or as an admixture, this is converted into free seequoxyd. If, during thio roasting, the temperature be kept pretty high, bnt a small quantity of neutral sulphate of zinc is formed, and that which has been already formed at a lower temperature, in large quantities, resolves itself into basic sulphate, evolving sulpbnrie acid, oxygen, and anhydrous sulphuric acid. The basie sulphate is decompescd to a free oxyd, only at a white heat. Tf the blend contains sulphide of cadmium, this acts in precisely the same manner as the sulphide of zainc, 9. Sulphuret of manganese, M" Se or MnS, found in combination with most of the sulphurets, and mill products from sulphur metals, whon heated to a red heat and air admitted, is decomposed to sulphate and red oxyd of manganese ; coutinued rousting at a red heat produces no change; at a higher tempcrature the sulphate formed is decemposed to sniphurous acid, oxygen, anhydrous sulphuric acid, and red oxyd. [To be Continued.) Dazu’s Maun.—The loss of this mill by fire on the 21st December, was a serious affair. The Virginia Union says: The ruin was complete, as nota fraction of machinery was saved. Whatever of amalgam or bullion was in pans, will of course be saved. Several hundred tons of ore were awaiting reduction. There was a large amount of salt in the mill, on storage, valued at $12,000, which was badly damaged. The insurance on the mill amounted to $15,000, There was about $15,110 insurance on the outbuildings, which, however, were saved. The entire value of the mill was probably not less than $150,000, Wo learn that Mr. Schamp, the superintendent, has, without any delay, leased the Ophir mill, and will immediately proceed to improve and fix it up after the style of the Dall mill. Asrertcan Cxtep Iron.—Five Amerieau chilled railway wheels have arrived in Londen. ‘They will be broken experimentally, and further wheels of this kind will be sent over for trial under Eughsh rolling stock. , We have samples of the iron from which these wheels are cast, and it is of magnificent quality. The fracture is a rich dark gray, medinm grained, and shows great toughness, the particles appearing to have been irregularly torn, rather than broken short off ‘The specific gravity ranges from 7.25 to 7.3185, and the tensile strength from 32,000 to 35,102 Ibs., or say 1414 to 16 tons per square inch. The iron is that known as the Salisbury cold-blast charcoal iron, and is worth about £10 per tou in New York.—Lngineering. Sl (

The Mining antl Scientific Dress, Communications. In THIS NRPARTMENT we invite the FRRE Discussion of all roper subjeets—correspondciits alone being responsible for he ideas and theories they advance. iWritten for the Mining and Setentific Press.] Progress of Metallurgy and Saving of Fuel. Messrs. Hnrrors.—It seems strange that with the abundance of ore we have in our mines, and the qnantity of fuel at our command, we are still obliged to send oves abroad for reduction, and afterward buy the metals at snch prices as the sméliers may choose to place uponthem. Itmustseem to outside observers that we neither possess the ores or fuel, so often mentioned in your valnable paper, or that we laek the knowledge of extracting the metals from the ores. Yet the fact is, we have both ores and talent in abundance ; and having in our favor the expeusive transport of ore to Europe aud the metal back again, we surely onght to compete suecessfully with the foreign manufacturers, not ouly in gold, silver and copper ores, but in ironaswell. If metallurgy had made no progress, and we had to resort to old modes of smelting, we still eould retain the field; but if we take into consideration the improvements made in the saving of fuel by various inventions, foremostamong which stands C. W. Siemeu’s, we shall find that we possess all wo need in our midst if we ouly take advantage thereof. Various experiments have been mace in the way of smelting works in California, and as far as gold and silver ore is concerued, I believe I was the owner of the only successful works ever erected in this State. For copper ores various experiments have been made with very poor success. The parties engaged in those experiments here had some theoretical, but not the practical knowledge necessary to make the proper calculation for desired results ; for if it had been otherwise, and they had formed a full knowledge of the . fuel and ore which they expected to mauipulate, they would not have speut their friends’ money in vain, and destroyed all, confidence in further euterprise. The impression has goue out that, as the Antioch smelting works were a failure, Mount Diablo coal is not fit for smelting ores. To this I respectfully dissent by saying it makes but little difference with regard to the character of the coal, whether it he anthracite, bituminous, lignite, or eveu wood, peat or sawdust; any material containing hydro-caxbon may be employed to raise as high a degree of heat as is necessary to smelt any metal or ore. Ali that is necessary is the proper Imowledge of the fuel and its apphecation ; with that we need never fail to produce the degree of heat requisite to effect the reduction of the ores of metals. Few of our mineralogisis have given this subject the proper attention it deserves ; but men of the greatest ability, like Professor Faraday, haye greatly ventilated the subject. I will give you a short abstract of what he has said on the subject of fuel, in connection with gas regenerating furnaces : ‘Gaseous fuel is obtained by the mutual action of coal, air and water, at a moderate ved heat, A brick chamber, perhaps six feet by twelve, and about ten feet high, is constructed with one of its end walls converted into a fire grate, 7. ¢., about half way down it is a solid plate, and for the rest of the distance consists of strong horizoutal plate bars, where air enters, the whole being at an inclination, such as that which the side of a heap of coals wonld naturally take. Coals are poured through openings above, upon this combination wall and grate, and being fired at the under surface, they burn at the place where the air enters ; but asthe layer of coal is from two to three feet thick, various operations go on in those parts of the fuel which cannot burn, for want of aiz. “Thus the upper and cooler part of the coal produces a large body of hydro-carbons ; the cinders or coke which are not volatilized, approach, in descending, towards the grate; that part which is nearest the grate burns, with the entering air, into carbonic acid, and the heat evolved ignites the mass above it. The carbonic acid passes slowly through the ignited carbon, becomes converted into carbonie oxyd, and mingles in the upper part of the chamber (or gas producer) with the former hydrdé-carbons. The water, which is purposely introduced at the bottom of the arrangement, is first vaporized by the heat and theu decomposed by the ignited fnel, and re-arranged as hydrogen aud carbonic oxyd; and only the ashes of the coal are removed, as solid matter from the chamber at the bottom of the fire bars. ‘These mixed gases form the gaseous fuel, The nitrogen which enters with the air at the grate, is mingled with them, constituting about one-third of the whole volume. The gas vises up a large vertical tube, from twelve to fifteen feet, after which it proceeds horizontally for any required distance, and then desceuds to the heat regenerator, throngh which it passes before it enters the furnaces. “A yegenerator is a chamber packed with fire bricks, separated so as to allow of the free passage of air or gas between them. There are geuerally four of them placed uuder a furnace. The gas ascends through one of these ehambers while air ascends through the neighboring ehamber, and both are conducted through one end of the furnace where, mingled, they burn, produciug the heat due to their chemieal action. Passing onward to the other end of the furnace, they (the combined gases) find precisely similar outlets down which they pass ; and traversing the two remaining regenerators from above downwards, heat them intensely, especially the upper part; and so travel ou in their cooled state to the chimney. ‘Now the passages between the four regenerators and the gas aud air are supplied with yalves aud deflecting plates, which are like four way cocks in their action ; so that by the use of a lever these regulators admit air or gas to the furnace. “Tt is to be observed that the intensity of the heated flame, which leaves the furnace for the stack, always proceeds downwards through the regeuerators ; so that the upper part thereof is most intensely ignited, keeping back, as it does, the inteuse heat. So effectually is this accomplished, that the gases which enter the stack to be cast into the air, are not heated above three hundred degrees of Fahrenheit. “Tt is cousidered that when the furnace is in full order, the heat carried forward to be evolved by the chemical action of combustion is aboutfour thousand degrees, whilst that carried back by the regenerator is about three thousand degrees; making an intensity of power which, unless moderated, would fuse furnace and all else exposed to its action. “Thus the regeuerators are alternately heated and cooled by the outgoing aud cutering gases and air. “Great facility is afforded in the management of a gas fuynace. Not merely can the supply of gas and air to the furuace be goyerned by valvesin the passages, but the very manufacture of the gas fuel itself can be diminished, or eveu stopped, by cutting off the supply of air to the grate of the gas producer ; and this is important, inasmuch as there is no gasometer required. “‘The economy in fuel is estimated practically as oue-half, even wheu the cheapest kind of fuel is used. Carbon, when burnt perfectly into carbonic acid, in a gas producer, evolves about four thousaud degrees of heat; but if burnt into carbonic oxyd, it only evolves twelve hundred degrees. The carbonic oxyd, in its fuel form, carries ou with it the twenty-eight hundred degrees in chemical force which it evolves when burning in the real furnace, with a suflicient supply of air. “The remaining twelve hundred degrees are employed in the gas producer, in distilling hydro-carbons, decomposing water, ete. . The whole mixed gaseous fnel cau evolve about four thousand degrees in the furnace, . to which the regenerator can return about) three thousand more.” In addition to the above, I can produce other statements, from more than fifty establishments where gas furnaces are used, and where a saving of more than 50 per cent. of fuel is effected. IT have not only seeu, but built and worked such furnaces ; and if our people would adopt them for metallurgical operations, we should not be obliged to send any more ore to a foreign country for reductiou. In my next I will give you a description of the application of petrolenm and coal tar for heating boilers, smelting and glass furnaces. J. Mosuemer. An Avanancaz.—A gang of Chiuamen at work on the Central Pacific Railroad, were buried by asnow-shde on the 22d December. Some four or five were dead when exhumed. The snow is from ten to fifteeu feet deep on the Summit. (Written for the Mining and Seicntifie Press.) PROCESS OF ROASTING ORES, ETO, Translated from the Germau of F. Plattner, for the Mining aud Gas-Light Jonrnal, New York. — ‘

BY J. H. TIEMANN, M. E. Numner Five. 8. Matt.—This mill product consists chiefly of F.25, Fe S in different proportions, so that either the F,?5 is in larger proportions than tho F, 8, or—which less frequently occurs—that the Fe § is in larger proportions than the Fe2S. Iu the former case we may suppose the matt composed of x(Fo 2S, Fo S)4+4(Fe 2S, Fe S) and in the latter case a8 x (Fe 2S, Fe S)+(Fe 28, nFo S), in which case, however, a small part of the protosulphide and subsulphide is sometimes replaced by other metals, as snbsulphide of copper, sulphides of lead, zinc, Manganese and silver; the matt also often contains slag mechanically combined, which, in a furnace matt containing sulphide of zine, and consequently difficulily fusible, may often amount to twenty per cent. When,ores consisting chicfly of pyrites, partly in a natural and partly in a roasted state, are smelted to a matt in a furnacc, under a covering of slag, the sesquoxyd of iron in the roasted part is reduced, ut the expense of the sulphur of the raw part which escapes as a vapor to a protoxyd, and combines as such with the earthy materials forming a slag, which afterwards combines with the slag used as a covering.* When the slaging (fluxing) is imperfect, wbich occurs when there is a lack of earthy material, particularly quartz, a part of the protoxyd of iron may be taken np by the matt, an oxysulphuret may be formed (™Fo25+I, O) and a matt may be formed haying the fermula, Fo? S+nyFe (8, O). If the ore was not free from other metals, which are likewise inclined to separate as sulphurets, they will be included in the compound. Pulverized matt, when roasted, acts similar to magnetic pyrites. If it be roasted at a low temperature and with proper precautions at first, besides free sequoxyd of iron, considerable quantities of protosulphate is formed, which, afterwards, a, an increased temperature, as in the case of that formed from mugnetie pyrites, is changed to persulphate under evolution of sulphurous acid; the anount fermed is abeut twenty-ono per cent., having seven per ccnt. of sulphuric acid. 4. Kupferkies (copper pyrites) Cu? S, Fo? S38 when roasted, acts similar to magnetie pyrites, except that besides a small quantity of persulphate of iron, a sulphato and free oxyd of copper is formed, If coarsely pulverized, copper pyrites be roasted at a dark-red heat and constantly stirred, and atmospheric air admitted until the smell of sulphurous acid disappears, it changes to a spongy powder, which, when cooling, chauges to a dark red color. This powder consists chiefly of sesquoxyd of iron, a suboxyd and protoxyd of copper, and contains protosulphate and persulphate of iron, and sulphate of copper—the latter in considerable quantities. If this product be now submitted to a bright red heat, and air admitted, the protesulphate of iron (as in the case of pyrites and magnetie pyrites) changes to persulphate; and there remains, besides the sesquoxyd of iron and the protoxyd of copper, only sulphate of copper and a little persulphate of iron with twenty per cent. of sulphurie acid. If the temperatnre be still increased, thcso sulphates are decomposed, leaving the free oxyds of iren and copper, the sulphuric aeid escaping partly as such, and partly as sulplmrous acid and oxygen. ~ 5. Kupferstein’ (copper matt). This mill product, when containing a high percentage of copper, consists principally of mCu 25, Fe S; when centaining a medium pereentage of copper Cz 8, Fe 2 8; and when having a low percentage, m(Cu? 8, F,2S)+Fe §, or in the latter ease is a mixture of eopper matt mCu2S, Fe S, witb iron matt Fe 2 8, F, §, in variable proportions, so that a eopper matt, with a very low pereentago of copptr, may have tbe composition (Cy 28, Fo 25)+Fe S$). The copper matt sometimes contains other sulpur metals, as lead, zine, manganese and silver, which replace one another; and is not always free from a mixtnro of sulphide of antimony or arsenic, which unito with the disulphide of copper, and pass jnto the matt. When pulverized copper matt is exposed to a dark red heat, and air admitted, it glows readily in consequence of the oxydation of its components ; at first it is converted into suboxyd of copper, sesquoxyd and protosnlpbate of iron, sulphurous aeid * When a part of the sesquoxyd has been reiuced only to magnetic oxyd (sesquoxyd plus protoxyd), and is present in any quantity, 1t crystallizes in beautiful glistening octahedrons, if the slag, iu a Jarge mass, be allowed to cool j slowly. passing off; but after the sulphides, being kept constantly stirred, have heen mostly oxydized, and the temperature increased decomposing the protosulphate of iron, it is converted into free oxyd of copper and sesquosyd of iron, with sulphate of copper and persulphate of iron, having abont eighteen per cent. of sulphnric acid; by continued roasting and constant stirring, tbe sulphates of copper and iron—the fermer only at a bright red heat—are decomposed, leaving free oxyds, while sulphurous acid, oxygen and sulphurie acid pass off—the latter in tho form of white vapors. 6, Bleiglanz (sulphide of lead) Pp S, when pulyerized and exposed to a dark red: beat, air being admitted, glows of itself in consequence of the ox_ ydation, evolves sulphurons acid, and at a continned dark red beat is converted into sulphate and free oxyd of lead. A higher temperature, not sufficient, however, to cause a sintering or smelting of tho free oxyd, produces no further ebange, for tho reason that the sulphate formed during the roasting eannot he decomposed and cenverted into fico oxyd. As the proportion between the snlphate and free oxyd varies in proportion to the amonnt of other metals present, this portion_of our snbject will he treated more fully further on, when wo come to explain the chemical changes which take place in the roasting of sulphur metals. 7, Wismnthglang (sulphurct of bismuth) B; 2 83, In a powder, when beated on a clay saucer ina muffel, just to redness, air being admitted, clows of itself, evolves sulphurous acid, and is very soon conyerted into a light grey powder without sintering (caking). This powder cousists of an oxyd and sulphate of hismuth. If the substanée contained copper pyrites, the product when cool has a dark yellowish green color. If this be heated in a glass tube to a bright red, it smelts, with the evolution of 2 little sulphurie acid, to a light brownish grey mass, which on the edges is translucent. 8. Zinkblond (sulphuret of zinc), yellow and brown, Zy S and Black F, S+3Z» §, is, of all sulphur metals whieb require to be treated by fire, the most difficult to roast. Even when in a fine pewder, it requircs an uninterupted red heat and strong draught of air for its complete oxydation, under whicb circumstances sulphurous acid is evolved, while free oxyd and more or less sulphate of zinc (nentral and hasic) is formed. If the blend contains irou sulphuret, cither as a component (blackjack) or as an admixture, this is converted into free seequoxyd. If, during thio roasting, the temperature be kept pretty high, bnt a small quantity of neutral sulphate of zinc is formed, and that which has been already formed at a lower temperature, in large quantities, resolves itself into basic sulphate, evolving sulpbnrie acid, oxygen, and anhydrous sulphuric acid. The basie sulphate is decompescd to a free oxyd, only at a white heat. Tf the blend contains sulphide of cadmium, this acts in precisely the same manner as the sulphide of zainc, 9. Sulphuret of manganese, M" Se or MnS, found in combination with most of the sulphurets, and mill products from sulphur metals, whon heated to a red heat and air admitted, is decomposed to sulphate and red oxyd of manganese ; coutinued rousting at a red heat produces no change; at a higher tempcrature the sulphate formed is decemposed to sniphurous acid, oxygen, anhydrous sulphuric acid, and red oxyd. [To be Continued.) Dazu’s Maun.—The loss of this mill by fire on the 21st December, was a serious affair. The Virginia Union says: The ruin was complete, as nota fraction of machinery was saved. Whatever of amalgam or bullion was in pans, will of course be saved. Several hundred tons of ore were awaiting reduction. There was a large amount of salt in the mill, on storage, valued at $12,000, which was badly damaged. The insurance on the mill amounted to $15,000, There was about $15,110 insurance on the outbuildings, which, however, were saved. The entire value of the mill was probably not less than $150,000, Wo learn that Mr. Schamp, the superintendent, has, without any delay, leased the Ophir mill, and will immediately proceed to improve and fix it up after the style of the Dall mill. Asrertcan Cxtep Iron.—Five Amerieau chilled railway wheels have arrived in Londen. ‘They will be broken experimentally, and further wheels of this kind will be sent over for trial under Eughsh rolling stock. , We have samples of the iron from which these wheels are cast, and it is of magnificent quality. The fracture is a rich dark gray, medinm grained, and shows great toughness, the particles appearing to have been irregularly torn, rather than broken short off ‘The specific gravity ranges from 7.25 to 7.3185, and the tensile strength from 32,000 to 35,102 Ibs., or say 1414 to 16 tons per square inch. The iron is that known as the Salisbury cold-blast charcoal iron, and is worth about £10 per tou in New York.—Lngineering. Sl (