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This new process, for which Letters Tatent have been granted in the United Slates, Great Britain, Canada and Newfoundland, may be understood from the specification of the liritish patent, sivcn below, to which are appended a series of explanatory notes and comments. The date of the patent in Canada is Jan. 14, 18G9, iu the United States, Feb. 9, 18G9, and in the United Kingdom, Aug. 1-3, 1869. SPECIFICATION. 1. For the extraction of copper from its ores by this process it should be in the state of an oxyd or some compound thereof, as oxychlorid or carbonate. These oxydized forms of copper are decomposed under proper conditions by protochlorid of iron, with the production of dichlorid of copper, Avhich is sokible in certain saHne solutions, and in some cases a portion of protochlorid of copper, together Avith insoluble peroxyd of iron, and more or less insoluble oxychlorid or basic persalt of iron, which may be rendered soluble by the action of sulphurous acid. 2. The naturally or artificially oxydized ores are to be digested with a watery solution of neutral protochlorid of iron, with or without the addition of an earthy or alkaline chlorid, as common salt. The neutral protochlorid of iron may be conveniently prepared by double decomposition of protosulphate of iron with an equivalent of clilorid of calcium or clilorid of sodium. In preparing the solution, here- inafter designated as the bath, we may proceed as follows : 3. One hundred and twenty (120) pounds of sea salt, or one hundred and twelve (112) pounds of dry clilorid of calcium, or its equivalent of hydratcd clilorid, arc to be dissolved with two hundred and eighty (280) pounds of protosulphate of iron, (green copperas,) in one hundred (100) imperial gallons of water. In place of the above salts we may substitute an amount of protochlorid of iron prepared by any other method, containing fifty-six (5t)) pounds of metallic iron. To the bath prepared in cither way, two hundred (200) pounds of sea salt are then added, Avhen the solution is ready for use, and will be found capable of chloridizing and dissolving about ninety (90) pounds of copper. The power of brine to dissolve the dichlorid of copper formed increases greatly with the strength • and temperature. The proportions above given arc convenient, but in the case of poor ores, a solution ot one-half the strength may be used with advantage. 4. In the treatment of copper ores by this process, they may be divided into two classes, non-sulphuretted and sulphuretted ores. 5. The first class or non-sulphuretted oxydized ores, includes the native oxyds of copper, the carbonates, and the oxychlorid. To prepare these for treatment they should be finely pulverized, and the carbonates may with advantage be gently calcined before or after grinding, in order to expel carbonic acid. The red oxyd, if alone or greatly predominating, should also be gently calcined after grinding to convert it into protoxyd ; but if it be mixed with a considerable proportion of protoxydized ore this is not necessary. 6. The pulverized oxydized ores thus prepared are to be digested in the above bath, with frequent agitation. Heat is not neces- sary, but it accelerates the solution of the oxyd of copper, which in practice should not be more than sufficient to yield sixty or seventy pounds of co[»pcr to the above bath of one hundred gallons. When the solution is complete and the liquid drawn off, the insoluble re- sidue should be lixiviated with a small volume of hot strong brine. The li(iuid is then digested with metallic iron, by which the copper is thrown clown as cement copper, two parts of iron yielding three parts of metallic copper. 7. The hath thus freed from copper contains a large amount of regenerated protochlorid of iron, and can be used at once to treat a fresh portion of oxydized ore. A. small loss of chlorine, which separates as oxychlorid of iron, has, however, to be supplied ])y add- ing to the bath, from time to time, protochlorid of iron or the salts required to produce it. This need not, however, exceed for each repetition, one-eighth of the original quantity, and by careful exclu- sion of the air the quantity to be added each time may be reduced to much less. The strength of the bath in protochlorid of iron should be determined from time to time by appropriate tests. 8. In localities where it may be desirable to economize the proto- chlorid of iron a modification of the process may be adopted, which consists in treating with sulphurous acid the iron compounds preci- pitated by the oxyd of copper. To this end sulphurous acid li-om the roasting of sulj)huretted ores, or from any other source, maybe made to pass over or through the bath after or during the process of dissolving the oxyd of copper. In this case the protosalts of iron are constantly regenerated, and serve to chloridize fresh portions of oxyd of copper. A small amount of protochlorid of iron, with the aid of sulphurous acid, may, in this modification, be used to convert a large quantity of copper into dichlorid, the excess of which is pre- cipitated, and may be washed out with hot strong brine. As this deposits a large quantity in cooling, the same brine may be employed indefinitely for dissolving dichlorid by heating and cooling it each time. 9. The sohd dichlorid is rapidly reduced by contact with me- tallic iron, especially when wet with brine, and yields metallic cop- per and protochlorid of iron, one part of iron giving two of copper. To prevent any precipitation of oxychlorid of copper from the di- chlorid solution by the air, it is well in all cases to have a small por- tion of protosalt of iron present. A little free sulphurous acid will also prevent such precipitation ; but any excess of this gas should be expelled or allowed to escape from the solution before adding metallic iron. 6 10. In the case of sulphuretted ores, tlio first step in the applica- tion of our ))rocess has for its object to convert the metal into an oxyd Soluble in the bath already described. This conversion is effected by calcination in the air, by Avhicli means all copper, iron and sulphur are oxydized. [Pyritous ores, holding much iron and sulphur, may be I'oastcd in hilns, then ground and recalcined, but native sulphurets, rich in copper, or regains, should be ground be- fore calcination, which is best done in a mufffc furnace. In cither case] a low red heat suffices, and what is called a ilead roast is to be avoided, not only because it involves a waste of time and fuel, but because the high temperature renders a portion of the oxyd of cop- per insoluble in the protochlorid of iron bath. The roasting need be continued only until the complete oxydation of the sul|)hurct of copper, and its conversion into a mixture of oxyd with a variable proportion of sulphate of copper. This product may be treated directly with the bath, Avithout addition, as directed for non-sulphu- retted ores, but the excess of sulphates thus introduced renders the bath impure, and much more metallic iron is required for the subsc(|uent precipitation than when the whole of the coytpcr is in the form of oxyd. 11. We therefore prefer to proceed as follows : We deter- mine in the roasted ore the amount of copper present as sulphate, which will vary very little for any given ore roasted under constant conditions, and we add thereto an cfpiivalent of lime, which gives rise to insoluble sulphate of lime and oxyd of copper. In practice it is well to leave undecomposed a small amount of sulphate of copper, which, in a subsequent stage of the process, will give with metallic iron the sulphate of iron re(![uired to replace the small loss already mentioned as occurring when sulphurous acid is not used. To an ore, for instance, with eight per cent, of copper, Avhich after roasting contains three per cent, of copper as oxyd, and five per cent, as sulphate, we may add lime enough to decompose four-fifths of the latter, at the rate of 28-0 parts of pure lime for 31-7 parts of copper, or about an equal weight of ordinary non-magnesian lime ; being four pounds of finely ground lime for each one hundred pounds of the above roasted ore. An equivalent quantity of carbonate of lime, or other alkaline or earthy base, may be used instead of quick- lime, but with less advantage. The roasted ore and lime may be «^ added to tlio bath together, or better, the ore is to be added first. The subsequent part of the process is to be conducted as ah-cady described for the ores of the first class. 12. When protosulphate of iron is used instead of the proto- chlorid in preparing the bath, or in keeping up its strength, as in . the case of ores of the first class, sulphate of soda is formed, which may in great part be crystallized out by extremes of heat and cold. The formation and accumulation of this sulphate may, however, be prevented by the use of chlorid of calcium as already set forth. The still larger production of sulphate of soda, which would take place if calcined ores of the second class were added directly to the bath, is prevented by the use of lime as already described, and that portion Avhich must result from the excess of sulphate of copper, as recommended, may be decomposed by the addition of small portions of chlorid of calcium from time to time. By attending to these precautions the strength of the bath in chlorid of sodium, and its sol- vent power may be indefinitely maintained. 13. We do not claim the use of any particular form of furnace, nor of any special arrangement for calcining, lixiviating or precipi- tating, reserving to ourselves the choice of the best forms of appa- ratus for these purposes ; neither do we cli\ ■.■^ the use of protosalts of iron otherwise than in solution, nor the use of perclilorid or other persalts of iron, nor yet the use of sulphurous acid save and except in connection with protosrHs of iron, as already set forth. 14. What we claim as our in^ ention is : I. The use and application of a solution of neutral protochlorid of iron, or of mixtures containing it, for the purpose of converting the oxyd or suboxyd of copper, or their compounds, into chlorids of copper. II. The use of sulphurous acid for the purpose of decomposing the oxychlorid of iron formed in the preceding reaction. KI. The use of a process for the purpose of extracting copper from its naturally or artificially oxydized compounds by the aid of the first, or the first and second of the above reactions, substantially in the manner already set forth. 8 EXPLANATIONS. Chforidizwg the Copper. — The reaction between protoxyd of copper and protochlorid of iron gives rise to pcroxyd of iron, and a mixture of the two chlorids of copper, two thirds being as dichlorid, and one third as protochlorid of copper, as shewn in the equation A. The red oxjd or dinoxyd of copper in like manner gives rise to peroxyd of iron, but yields a mixture of two thirds dichlorid and one third of metallic copper, as shown in the equation B. A. — 3Cu,0, +4rcCl = 2Fo,03+2Cu2Cl + 2CuCl. B. — 3Cu",0 + 2roCl = Fc2 0, + 2Cu,Cl-t-2Cu. Inasmuch as the metallic copper (2Cu) set free in B. is readily converted into dichlorid by the protochlorid, (2CuCl) of A, it fol- lows that if not more than one half of the copper be dinoxyd, the remainder being protoxyd, the whole will be chloridizcd by the action of the protochlorid of iron bath. Soluhility of the Dichlorid of Copper. — While the protochlorid of copper is very soluble, the dichlorid is insoluble in water, but readily soluble in a strong solution of sea-salt, and of most other chlorids. A saturated brine at a temperature of 194° Fahrenheit ^ (90° Centigrade,) will hold in solution more than 16 per cent, of dichlorid of copper, and at 104° F. (40° C.,) more than 8 per cent. A brine containing fifteen parts of salt to one hundred of Avater, dis- solves at 194° F. (90° C . ) 10 • per cent., at 104° F. (40° C.) 6-0 per cent., and at 57° F. (14° C.) 3-5 per cent, of dichlorid of cop- per. When these strong solutions are diluted with water they deposit much of the dichlorid as a white crystalline powder. A solution made with five parts of salt to one hundred of water, dissolves at 194° F. (90° C.) only 2-6 per cent., and at 104° F. (40° C.) only 1 • 1 per cent, of dichlorid of copper. The above figures are approximate and a little below the results of actual experiment . 100 parts of dichlorid contain 64 parts of metallic copper. Composition of the Bath. — The equivalent weight of j^rotosul phate of iron or copperas is 139, and that of common salt 58 • 5, ivccn protoxyd of 'oxyd of iron, and 1 being as' dichlorid, in the equation A. nner gives rise to irds dichlorid and ition B. + 2CuCl. 2Cu. 50 in B. is readily :!uCl) of A, it fol- r be dinoxyd, the hloridizcd by the e the protochlorid iblo in water, but ind of most other 194° Fahrenheit, 1 16 per cent, of Q than 8 per cent, .red of Avater, dis- :° F. (40° C.) 6-0 ' dichlorid of cop- vater they deposit rder. A solution ^ater, dissolves at •4'"F. (40° C.) ibove figures are experiment. 100 per. iight of protosul mmon salt 58 • 5, \ J/./ " while that of copper is 347, and that of iron i the proportions for the bath, numbers a little given, to allow for impurities in the salts erapl three equivalents, say 95*1 pounds of copper, of protoxyd, two e(piivalent3 of protochlorid ( from 280 pounds of copperas and 120 pound 100 imperial gallons or 1000 pounds of v;ater. convert one third of the copper into protochlori dichlorid, equal to 98*9 pounds of dichlorid of this soluble we have prescribed the addition of cent, additional of salt to the bath, Avhile, as wc holding but 15 per cent., will dissolve at 194° ] than this quantity. While these are the theore is in practice, from a secondary re-action resul of an insoluble basic per-sait, a loss of protocl] ing to from five to ten per cent. , so that the c the bath is somewhat less than above represen considerable portion of dinoxyd of copper be [ amount of dichlorid will be larger than above ci of these reasons it is not well to add to the al 60 or 70 pounds of copper for each 100 gallo the copper from a properly prepared ore wi by several hours digestion or percolation, eve more rapid in proportion as the heat approach Preparation of the Ores . — In the calcinati recommended, the object is to expel the carboi otherwise cause mucb effervescence in the batb dinoxyd predominates in the ore, this should be, verted into protoxyd by calcination in the air, leaves one third of its copper undissolved in tb ing sulphuretted ores by roasting till all the there is obtained a mixture of sulphate of coppi a portion of dinoxyd, which latter, according to P to 20 or 30 per cent, of the copper. Farther ror will convert both this and the sulphate into pr( dition is less advantageous, inasmuch as botl: 10 consumed and the copper is rendered less soluble. The large pro- portion of dinoxyd, moreover, suffices, as already explained, to con- vert much of the protochlorid of copper into dichlorid, thereby effecting a saving of iron in precipitating. Consumption of Metallic Iron. — With few exceptions the copper extracted by solution from its ores is thrown down in the metallic state as cement copper, by means of metallic iron. In theory there are required less than 89 (88*3) parts of pure iron to precipitate 100 parts of copper from a solution of protosulphatc or protochlorid, but in practice two or three times as much are consumed. This great consumption of metallic iron is due to two principal causes : 1st. In the ordinary processes for extracting copper from its ores by the moist way, acids (and sometimes pcrsalts of iron) are employed to render the copper soluble, either as the principal agents or as auxilliaries. When these are employed the solutions contain more or less of persalts of iron, which consume the metallic iron that would otherwise throw down the copper. Thus an amount of persulphate holding four equivalents of iron consumes five equivalents of metallic iron, and is thereby converted into protosul- phatc, depositing at the same time four equivalents of iron in the form of an insoluble basic persulphate, which contaminates the cement copper. 2n(l. The second cause of the waste of iron is the action of the air. In order to separate the whole of the copper from the solutions a digestion of several days with metallic iron is resorted to. The protosalt of iron, which is formed in this re-action, greedily absorbs oxygen from the air and is thereby converted into a mixture of an insoluble and a soluble persalt. The latter, as above shown, dis- solves a quantity of iron in its turn, and yields another portion of insoluble persalt, which falls with the cement copper. The result of the above causes combined is that histead of 89 parts of iron there are consumed,according to circumstances, from 200 to 300 parts of metallic iron to produce 100 parts of metallic copper in the form of cement copper. This, too, is rendered impure by an admix- ture of insoluble persaits of iron, generally amounting to from 20 to 40 per cent., and even more. The present process avoids both of 11 these faults, and enables us to obtain a pure cement copper with a very small consumption of iron. The solution obtained with the bath of protochlorid of iron can contain no persalt of iron in solution, and if protoxyd of copper alone has been employed will hold three equi- valents of copper combined with two equivalents of chlorine, so that they will be precipitated by two equivalents of iron, being at the rate of r)9 parts of metallic iron for 100 parts of metallic copper. If, from the presence of much dinoxyd,or from other reasons, the greater part of the copper be present as dichlorid, it will be remembered that this requires only one equivalent of iron to precipitate two equivalents of copper, being at the rate of 45 parts of iron for 100 parts of metallic copper. The precipitation of copper from the solutions is at first rapid, especially if these are hot, and kept in agitation. Inasmuch as the waste li(|Uors are not rejected in this, as in the ordinary process, the long digestion with iron rc(i[uircd to remove the last portion of cop- per is dispensed with, and the \h[\ik\, after having given up the greater part of its metal, is withdrawn and used for the treatment of a fresh portion of ore. The prolonged action of the air on the bath is thus avoided, and avc obtain a cement copper almost entirely free from insoluble iron salts, and with the consumption of a minium quantity of iron. The RegcrifraU'dBath. — If the action of the air be excluded it will be found that the bath, after complete precipitation of the cop- per by iron, will be nearly as rich in protochlorid of iron as before the solution of the copper. The loss, which is due to the separation of a i)ortion of oxyehlorid of iron during the solution, is variable, and in some cases does not exceed six per cent. The various ways of supplying this loss are three : (1) The direct addition to the bath of a portion of protosulphate or protochlorid of iron. (2) The addi- tion of a portion of sulphate of copper from the roasted ore, and (3) the use of sulphurous acid. Of these the first requires no explana- tion, and the second and third will be explained mider the two fol- lowing headings. The proportion of iron in the bath should bo determined from time to time by the following method : A small por- tion of the bath, freed from cojiper by digestion for some hours with metallic iron in a stoppered bottle, is diluted with 50 parts of water, 12 and strongly acidulated with sulphuric acid. A standard solution of permanganate of potash of known strength is then added from a graduated tube so long as it is decolorized. By comparative experi- ments of this kind on tlie regenerated bath its strength in proto- chlorid of iron is readily determined. Tlie Protosalts of Iron. — In preparing the bath wo have recom- mended either protosnl[thate or protochlorid of iron. The f )rmer salt, being an article of commerce, is to be obtained in many places where the latter cannot readily be procured, and may be easily manufactured for the purpose in regions where neither of these can be readily obtained, provided sulphuretted copper ores are to be had. It is Avell known that in roasting these a considerable portion of the copper is converted into sulphate, which may be readily dissolved by water from the roasted oro. If to each G3.4 pounds of copper thus dissolved, we add 120 poimds of common salt, and digest tho liquid with metallic iron in a close vessel, best with the aid of heat, till the copper is precipitated, the solution will contain such an amount of protochlorid of iron that it will only be necessary to add 200 pounds of common salt and a sufficient amount of water, to make 100 gallons of the bath of the strength before prescril)ed. If a roasted ore, charged with sulphate, be added directly to the bath of protochlorid of iron, it will be found, after precipitating the copper by metallic iron, that the regenerated bath will contahi not only the protosalt of iron, corresponding to that originally present in the bath, but also that resulting from the action of the metallic iron on the sulphate of copper introduced, which has given rise to proto- chlorid of iron and sulphate of soda by double decomposition ; thus rendering the bath impure both from the presence of sidphtites and from an excess of protochlorid of iron. To obviate these results wo add to such roasted ores, (as already described in § 11), so much lime as may be necessary to convert the whole or the greater part of the sul- phate of copper present into insoluble sulphate of lime and protoxyd of copper, which latter is at once soluble in tho protochlorid bath. A small portion of sulphate of copper as above prescribed, may bo left undecomposed by lime, and by its re-action with metallic iron ■will give the protosulphatc of iron rc( quired to supply the small loss 13 already explained, and keep up the regenerated bath to its original standard, as shoAvn by the test "s\'ith permanganate. The use of protosulphato of iron for making the bath, introduces a large proportion of sulphate of soda. A large amount of this, it is true, crystallizes out when the bath is exposed to cold, and may thus be got rid of. The use of a portion of chlorid of calcium may also, as already explained, be resorted to with advantage Avherc this substance can be cheaply procured. In districts ■where hydrochloric acid is a bye-product of little value it will be best to obtain the protochlorid of iron directly by saturating the crude acid with scrap iron and employing the product as already explained in § 3. Use of Sulphurous Acid. — When the mixture resulting from the action of oxyd of copper upon the bath of protochlorid of iron, is heated and exposed to the action of an excess of sulphurous acid, the whole of the separated peroxyd of iron is converted into a protosalt, and the bath, after precipitation by metallic iron, is found to contain much more protosalt than at first. Such a result is of course to be avoided, but by passing into the bath a small portion of sulpluirous acid towards the close of the digestion, it is easy to dis- solve such apportion of the precipitated oxychlorid or oxyd of iron as to prevent the loss of iron which otherwise occurs, and keep up the standard of the regenerated bath Avithout the addition of a salt of iron or of sulphate of copper. Solvent Power of Protocldorid of Copper. — Protochlorid of cop- per readily attacks metallic copper, forming with it dichlorid. Hence, as already explained, the metallic copper which is separated when the protochlorid of iron bath acts on dinoxyd of copper is at once dissolved if an e(i[uivalent of protoxyd of copper be present to yield the reipiisite amount of protochlorid. The protochlorid of copper will also attack the certain sulphuretted compounds of copper. Cop- per glance, purple copper ore, or artificial products as regulus approaching these in composition, are readily dissolved by a solution of protochlorid of copper mixed with common salt, dichlorid of cop- 14 per being formed. Hence, a sulphuretted ore Imperfectly roasted, and still containing a small portion of sulpliuret, rich in copper, m\i give it up to the action of a bath containing protochlorid of copper. For further information address, T. Sterrt Hunt, Montreal, Canada, James Douglas, Jr., Quebec, Canada, or their Agents, James Leavis & Son, 1 Femvick Street, Liverpool, Eiujland. ^