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 [I'UAN-ACllU.S.- i.iK llli: AMI KI'W IN>llTt IK nV MlMNd lONulNLliUS.J 
 
 Tllh: UYbKOMICTALLUUdV OF rol'l'i:!!. A.M> ITS SEl'AliA- 
 riON FUOM rilK I'UFCIOIS MIJTALS. 
 
 
 i;V T. >l'KltllY IIINI'. I.l-.1>., IMi.S., MON ritKAl,, ( ANAUzV. 
 
 (li.M.I ;il llir \ irniiiin M-Ttiiig, .lull.', IS.Sl.) 
 
 Wkt pnn'osses for tlic extraction of coppcM- tVoui its ons li;ivt> of 
 late attracted imicli attention, especially in Kuiope, where the use 
 of cupriferous iron-pyrites as a source of suljjhur prevails. These 
 processes present an aihlitional interest, when, as is often the case, 
 the copper-ores to he treated contain one or hoth of the precious 
 metals, .since the complete separation oi' these from (!0])per, eitlu'i' in 
 the drv or the moist way, is, as is well known, one of the diilicnlt 
 prohlems of metalhiri>y. The principal wet processes hitherto in 
 use for the extraction of copper from its ores may he included under 
 three classes : 
 
 I. Those in which the copper in sulphuretted ores is rendered 
 soluble in water hy caleininjj; them, after a preliminary roastinj;' 
 which removes the t^reater part of their sulphur, with a portion of 
 common salt, hy which the copper is converted into a chloride ([.ong- 
 maid and llenders(Mi), or with sulphate of soda, hy which sidphate 
 of copper is formed (Monnier). Allied to these is the method by 
 which a portion of the copper is got as soluble sulphate by roastin-^- 
 without addition, a process whieh is sometimes modilied and rendered 
 more complete by re-roastinj,^ the lixiviated residues with the addition 
 of a ])ortion of raw sulphuretted ore (Baidcart). 
 
 II. Those methods in which free ehlorhydric or stdpluirie acid is 
 used to dissolve tlie copper from oxydi/ed or roasted ores. The.se, 
 while simple and ellieient, are too costly, exee])t in certain localities 
 where ehlorhydric acid is a waste i)roduet. Related to tliera is the 
 plan which Consists in exposing the oxydized and moistened ores to 
 the slow action of sulphurous acid mixed with air, by which a 
 soluble sulphate of copper is formed. It has been proposed to de- 
 compo.se the solutions of sulphate or chloride of copper by sulphur- 
 retted hydrogen, thus separating the copper as suli»hide, and using 
 the liberated acid to dissolve fresh portions of oxydized copper. It 
 
 1 
 
 flM|gMneuM>^Mi^ ^ 
 
 (ii 1 narfJA »*»•««*»' •-^- 
 
 \: 
 
 a^ !W i i i .nir- il M»^i ii w . J^c»iMi iKi!Bswafta.g aiiM 
 
IJYDUOMKTArj.UlUiY OK COl'PKK. 
 
 is, liowovcr, the almost univ(>rsal practice to throw down tlie copper 
 from its solulions, however ohtaiiied, in the metallic stat(' by the use 
 of iron, either serai»-iron or iron-spon,i-e, although in some instances 
 milk of lime has been used as a precipitant, by which oxide of copper 
 
 is |)roduced. 
 
 111. The method in which a hot solution of ferrous chloride, with 
 common sdt, is used to chloridize the oxydizod copper and (convert 
 it into a mixture of cupric and cuprous chlorids, which latter, thouj>;ii 
 nearly insoluble in water, is dissolved by help of the chloride of 
 sodium. From this solution the copper is precipitated by metallic 
 iron, thereby rcj.roducing the ferrous chloride, and regenerating the 
 solvent, an advantage which this process possesses over any other 
 whieli gives the copper in the metallic form. This, which is known 
 as the Hunt and Douglas method, may, in many cases, be used with 
 advantage for the treatment of low-grade copp«'r ores, and, as the 
 neutral solvent does not dissolve either arsenic or antimony, enables 
 fine copper to In; got directly from ores ht.lding these; impurities.* 
 
 AVhen, however, it is applied to the treatment of copper-ores con- 
 taining silver, the use of the bath of ferrous chloride and chloride of 
 sodium has, in common with the method of roasting with salt, the 
 disadvantage that it converts the silver into a chloride which is 
 soluble in a strong solution (»f chloride of sodium and is then with 
 dillicidty separated from the chlorides of copper. T'lu; separation of 
 silver and c..i.i>er when dissolved together in the state of chlorides 
 has greatly exercised (he ingenuity of metallurgical chemists from 
 its importance in connection with the treatment of Spanish and 
 Portuguese pyrites, now so extensively used in (jreat Britain as a 
 source' of sulphur, where their consumption in 1877 amounted to 
 G00,000 tons. These ores contain on an average about forty-nine 
 per cent, of snlphin- and two or three per cent, of copper, with a 
 little silver, wpial, according to Claudet, to from twenty to twenty- 
 eight grams to the ton of ore, and traces of gold. The residues 
 alter calcination still retain three or four per cent, of sulphur and 
 about four per cent, of coi)per, with sixty per cent, or more of iron, 
 
 * The liydn.us .silicalo of copjuji- (clirysocolla) is, liii.! tiio cufboimU's of copper, 
 complfUOy<l.>cni.>po^,.d bv a hot solution of f.-n-ous ohlorid.^ with eomnion salt. 
 An aooounlof tho nppliciition of this method to the treutn.unt of a crystalline 
 hydrous silicate of alumina, mi'.i^nesia, and copper (which is essentially u coppor- 
 ciilorite, and has been described by the writer as a new species under the name 
 of vcnerile), will be found in the Transactions of the American Institute ot 
 Mining Engineers, vol. iv, p. 328. 
 
 
TUK nYHHoMKTAr-I.t'KOY OF rOPr'I'.l!. 
 
 3 
 
 lie (M)i)j)Oi' 
 
 )y tlio use 
 
 iiistaiici'.s 
 
 <»!" cupiuT 
 
 rido, witli 
 1(1 (ioii'.'crt 
 iv, ihoiiifli 
 hloride of 
 y inotallic 
 rating tlie 
 any other 
 is known 
 used with 
 md, as the 
 ly, enables 
 lU'ities.* 
 •-ores con- 
 ['hloride of 
 ii salt, the 
 i which is 
 then with 
 |)aration oi" 
 f chlorides 
 mists from 
 »anish and 
 Jritain a& a 
 nountcd to 
 forty-nine 
 per, with a 
 to twenty- 
 lie residues 
 Lilphur and 
 )re of iron, 
 
 ti"s of copper, 
 L'omnion salt, 
 a prystalline 
 tilly 11 eoppor- 
 d(;r the name 
 1 Institute of 
 
 e 
 
 /J 
 
 
 chiefly as peroxide. This material, after havinj; Ihu'U af^ain calcined 
 for some hours ata low heat in a reverl)eratoiy with about fifteen ]n>r 
 cent.of conimon salt (or, as at Oker in ( icrinany, with crude chloride 
 of potassium), j^nvcs u|) to water aci<lulatcd with a little chlorhydric 
 acid its stilphur as sulphate of soda, and its copiM-r and silver as 
 chlorides, tojjjethcr with a considerable excess of common salt, leaviiij;- 
 V)chind a nearly pure peroxide of iron with not over two thousandths 
 of copper. A miiuite portion of jjold, which was converted into 
 anrous chloride during the roastiiii^, is also present in the solution.* 
 The lixivium, in an example given by Claudet, had a specillo gravity 
 of 1.'24, and held in a metre-cube, l)esides 1 14.0 kilograms of sid- 
 |)hatcof soda, 04.0 of chloride of sodium, and 52. S of copper as pro- 
 tochloride, besides small portions of zinc iuid iron, with a little lead, 
 and 44 grams of silver. The above details of the salt-roasting pro- 
 cess, which have often been published, are here repeated in order to 
 bring more clearly befon; us the problem of separating the silver 
 from the copper. 
 
 Various plans have been suggested for extracting from such solu- 
 tions as the al)ovo the dis-solved silver before throwing down tlii' 
 copper by metallic iron. It has been proposed to |)recipitate tli(! 
 silver by finely-divided metallic copper, as is done; in the .\ugustiu 
 process from .solutions of chloride of sodium holding oidy dissolved 
 silver-chloride; but, since metallic copper at one(> converts prolo- 
 chloride intodichloride of copper, it becomes necessary, as a prelimi- 
 nary to the precipitation of the silver by this means, that the whole 
 of tlie copper in the solution shoidd first bo brought into the latter 
 condition. This may be effected by treating the hot solution with 
 sulphurous acid, or by filtering it at a temperature near the boiling 
 point through a layer of coarsely-ground copjier matte, or of vitreous 
 or purple copper ore, from which, as I have found, a second equiva- 
 lent of copper is taken up. From solutions holding the whole of 
 the copper as dichloride, the silver may be readily thrown down in 
 the metallic state by filtering them through a layer of finely-divided 
 
 * rinttner, us is woU known, showed tlintj^old, like .silver, is cliloridizcd when 
 pyritous ores containing; it aro roasted at a low red lieat witii coninion salt; 
 an aiiroiis chloride being apparently found, which, in the presence df chloride of 
 sodium has a considerable degree of stability, though it is decomposed at higher 
 temperatures. This chloride of gold is insoluble in water, and, unlike chloride of 
 silver, is not decomposed by mercury. It is butslightly soluble in brine, (hough 
 readily dissolved by a solution of hyposulphite of soda or lime. A process (iro- 
 posed by Kiss for the simultaneous uxtraction of silver and gold from pvrilous 
 ores is based on these reactions 
 
 
I'liK l[^■m{»)^fK•|•AI,r,I'^^Y of coim'kh. 
 
 inctallir copiuT ; l.iif, iiiasmiicli as (lie diplilorido r('f|iiiivs to hold it 
 in solution, a -rival vol u mo of lio( ronccntralcd l)riiii','= tins method 
 oCscparatiiifr silver Iroiii solutions eontainiiiii; a ennsich'rahle amount 
 of eo|>|ier is not in all eases praetieahle. 
 
 Anionn- the plans whieh have Ijeen proposed (op the separation of 
 (he silver from these saline solntions are those l.ased on frueti.,nal 
 pivcipitatioii. This is effoeted, as at Oker, by the nse of snlphido 
 of sodium; or hetter, hy diluted sulphuretted hydroi;cn .ir.'is, as 
 i^(^l \)y the aetion of air mixed with earhonic a(.'id on the waste; eul- 
 eiiim-sulphide from Lehlane's soda-j)roeoss. In the latter ease, tliu 
 whole of the silver is, accordinjr to fJihl.s, earried down with 
 the (irs( six per cent, of the eopper. Siielus blows (inely-divided 
 metallic iron into the solution, and duds the first twenty p<'r eeut. 
 of eopper thus precipitated holds four-fifths of the silver. l''or the 
 extracdon of the silver from the mixed sulphides it suilices to con- 
 vert the silver into a sulphate, as in the Ziervofrol i)ro(!ess. For the 
 separatimi of silver from preeijiitated copper, J. A. Phillips, by a 
 proress patented in 1,S77, makes the material into a paste with water 
 and a mixture of eommon salt and earbouad" of soda ; and, after 
 calcination in a revorberatory, ;;cts the silver in the form of chloride, 
 which is dissolved out by brine from the oxidized copper. 
 
 The solvent power of solutions of chloride of sodium li)r chloride 
 of silver is diminished by dilution, and ujion (his ilict, apparent Iv, is 
 based !i process for the separation of silver, patented iu 1S77 in (ireat 
 FJritain by Jardine t^- f 'hadwich, which consists iu dilutina; the stroujf 
 lixivium from the salt-roasted ore to about specific j>;ravity 1.10— 
 1.12, and adding thereto, in the form of a dilute solution, about 
 half a pound of acetate of lead to the ton of liipiid. The precipi- 
 tate, whieh after a time separates, consisting, in large part, ofsidphate 
 of lead, carries witti it a portion of chloride of silver, and, it is said, 
 a trace of gold. 
 
 The most elegant method for the separation of silver from these 
 mixed solutions is, however, that patented by Claudet, and ext(>u- 
 
 * 100 CO. of a solution liolding ir).0 ^'nuns of chloride of .sodium, dissolve at 
 90° C, 10.0 griims ; at 40°, ti.O; and al 11°, ,1.5 -raiii.s of cuprous .■iiloridc ; wiiilo 
 100 cc. of a solution iioldin^' '>.() grains of clilorid(! of sodium, dissolve at !)0° 
 2.0 grams, and at lO", 1.4 .irrains of cuprous cliloridc. Tliissul>staiico, contrary to 
 the received statements, is not .piitr in>ohilili' in water When tlie eupnius 
 ehloride is hoiled witli distilled water an amount eijual to about 1.3."i !;riim> to a 
 liter pav-es into .solution, and is in p.irt tlirown down on cooling in a white cry.- 
 lalliiie form; the solution, at 14<^ C, still retaining about 6^90 grams to the 
 liter. The above numl>rs are only ap|]roxiniatiMn-, 
 
 i 
 I 
 
THK IIVlinOMKTATJ.Unc.V <)\' foPrKR. 
 
 iros to hold it 
 * this method 
 orahk' atnoiint 
 
 ! separiition of 
 I on rrucliwiiiil 
 ■ic ol' •^iil|ihi(l(' 
 rot;('ii .iras, as 
 the WA-io. cal- 
 iittor caso, lh(! 
 I down willi 
 (iiic!y-dividc(| 
 I'lity per cciil. 
 ,'C'r. Vny tlu' 
 ulliocfj to t'oii- 
 !(,'8s. For the 
 Phillips, I.y a 
 -ti' with water 
 la ; and, al'tei' 
 ni ol'ehloridcj 
 )er. 
 
 n Ii)r chloride 
 apparently, is 
 IS77 in (Ireal 
 iiiu; the .strontf 
 ravity 1.10— 
 )lntion, ahoiit 
 The preeipi- 
 ■t, oi'sidphato 
 lid, it is said, 
 
 er iVoni these 
 t, and oxton- 
 
 imii, dissolvr lit 
 cliloi-idc; wliili' 
 dissolve at 90° 
 MC'O, contrary t') 
 en tlii^ cuiiroiis 
 l.S'i giaiii> to a 
 in ii wliito cry.-- 
 grains to the 
 
 sivoly applied in (^ireat IJritaiii. It depends on the alin<isl eoinplete 
 insoluiiility ol' iodide ol' .silver in solutions of chloride of sodinni, and 
 •'oiisists in addino; to the lixivinni. in which the proportion of dis- 
 "^olved silver has previonsly heen determined, a dilute solntion of a 
 solnhlc iodide jnst sullieient in amonnt to convert the whole of the 
 silver into iodid(! of silver. The precipitate which .separates after 
 forty-eiLrht honrs of re|tose, is washed with ililnte ehlorhydri(! aciil 
 to remove adherent cop|)er--salts, and then consists chiefly of a 
 mi.xtnre of sidphate of lead with iodide of silver, which is reduced 
 l»y metallic zinc, the iodint^ heiiio- thns recovere<l for further use, 
 'J'reatcd in this manner, the calcined S|ianish ores yield to the ton 
 2(» grains of silver eontainino; 1.,'} per c(Mit. of gold, anioiniting, ac- 
 cordino- to Luniie, to ahont two-thirds the entire ;unounl of precious 
 metals contained in the ore. The presonect of dichloridt^ of copper 
 in the solution interferes, hy the |)ro(luetion of a cuprous iodide, with 
 the separation of the silver as iodide ; and hence the calcination ol' 
 the ores with .salt must I)e so conducted as to give the copper in the 
 condition of protoehloride.* 
 
 The extraction of coppei" from its ores by roa.sting with salt is 
 limited to |)yrit')im ores poor in copper, which yield, hy their pre- 
 vious calcination, a large proportion of pero.vide of iron ; the pres- 
 ence of this being necessary to the eil'ectual ehloridizing of the copper 
 in the furnace. When a])plied to richer ores this method fails to 
 render the whoh; of the copper soluble, for reasons Nvhieli are made 
 a]»parent b,- the investigations of Mr. Thomas Miicfarlane, dcscribe(J 
 by him in 1805. lie found that wliile copper-ores, such as chalco- 
 pyrite and bornite, when calcined with salt, either alone or with an 
 admi.xture of pulverized (piartz yield but a small portion of their 
 copper in the form of solubl i"'oride, such a mixture of on^ aail 
 salt, with twice its weight of pe xido of iron, and a little pyrites to 
 furnish additional sulphur, if calcined at a low terapcature, and 
 without stirring, gave up nearly all its copper to water as a soluble 
 chloride. It was m.adc evident, from these and other experiments 
 described by Macfarlanc, that the mass of heated peroxide of iron, 
 in the presence of air, favors the conversion of the sulphur into a 
 sulphate, through which the decomposition of the common salt and 
 the ehloridizing of the copper is effected. f 
 
 * For nn excellont account of wet |)r(jcc?sos for Ihf extraction of copper, sno 
 Friedr. Bode, in Dingler'.s Polytechnischcs Journal for .January Marcli, 1877, 
 ^ol. ccxxxi, pj). 254, o57, 428. 
 f Canadian Naturalist, second series, vol. ii, pp. 219-2M1, and vol. iii, p. 4o7. 
 
6 
 
 rm; iivDuoMK'iAi.i.niKtY of copi'ku. 
 
 TIk's.' roiidiiiuiis arc most fully milizcd wlicii a iiiafcriul liUc tlii' 
 ••alciiirtl residue (if Spaiiisli pyrites, (•(.iitairiiiiM' in KM) parts a!«.iit I 
 parts each of cMpper and snlpliiir, and SO part- or timre ..f p(>r(i\ide 
 <•( irnii, is eali'ined with a siiHieient aiiKnuil olCdiiinioii salt, in wliieli 
 ease, as we liavc seen, llie elil()ri<lizin,i,' of tlie copper \h nearly coni- 
 |»i"te. I^rnoranec of tlicHc conditions lias ?nore than once lei to 
 lailnre in attempts to apply this process of copper-extraction. 
 
 ITrdike the nictliod of chloridizintj by roustin;,' with salt, that de- 
 pend inij; on the nse of ii solntion of ferrous chloride with salt is a 
 KiMieral on.-, applicahle toall natii'-ally or artificially oxidized copper- 
 ores, which may he readily and cheaply chloridizod by its aid.* 
 When applied to copper ores coiitaininu; silver, however, this shares 
 with the salt-roastinjf process the disadvanta.<i;e that the silver is at 
 the same time chloridi/ed, and if not present in too Iar>^e an amount, 
 is dissolved, while the dichloridc of copper formed by the reaction 
 between the oxide of c()p|)er and the ferrous chloi'idc precludes tlio 
 use of ("laudet's method of precipitatinjr the dissolved silver by a 
 soluble i(Mlide. 
 
 There is a large; olass of coppor-boiirinj^ ores and furnaco- prod nets 
 containiuj,', besides silver, and in some oases frold, portions of anti- 
 mony and arsenic, often accompanied by lead, the treatment of 
 which, either by the wet or the dry way, oifers many diilicultics. A 
 simple and economical ^roiieral method, which will elfect a complete 
 separation of copper from silver and }j;old on the (mo hand, and from 
 Jirseni<', antimony, and lead on the other, has hitherto been a <lesi<l- 
 cratnni in metallurgy. From the want of such a process considerable 
 qnantitifs of refined copper extracted from western ores and mattes, 
 and carrying from 10 to 50 onnoes of silver per ton, have of late voars 
 )ecn sold in our inarket.s. 
 
 With my friend, Mr. James Douglas, Jr., of PlKcuixvillc, I'a., I 
 have devoted much time to the metallurgical problem thus |>rc- 
 sente(l,and as the result of our joint labors have now to bring before 
 the institute of Mining Engineers a novel wet process for the ex- 
 traction of copper from its ores, which will, I think, be found to 
 meet the required conditions. The new method is based upon the 
 reaction described by Wahler between sulphurous acid and a solu- 
 tion of protochloride of copper, which gives rise to insoluble diclilo- 
 ride with the elimination of one-half the chlorine in the form of 
 
 * A process of ooppcr-pxtructioii, based on this principio, is tlio sulyect of 
 UnilPti Stiitcs k'ttcrs-piitciit, !;raiitpd to T. Storry Hunt and Jiinies Douglas, .Jr., 
 February 9th, 1869. 
 
 ".._U " ' J"l " 
 
I'liK MVim«>MFrr.M,r.i;Kf»v oi' cofpiii:. 
 
 atcriiil like the 
 ) parts altdiit I 
 )!'*' i)\' |i('ni\i(Ic 
 1 salt, ill wliii'li 
 
 is nearly com- 
 ;ii once lr 1 to 
 I'actioii, 
 
 li salt, that <l<'- 
 witli salt is a 
 kidi/cd coppcr- 
 il by its aid.* 
 .'cr, this shai'i'H 
 till! silver is at 
 ')*i' an aiiininit, 
 )y the roaetion 
 
 precludes the 
 I'd silver hy a 
 
 rnaeo-prodiiels 
 rtioiis of anti- 
 treat iiieiit of 
 liilieiilties. A 
 eet a (•onipleto 
 and, an<l from 
 > been a <lesi<l- 
 ^s eonsiderahle 
 es and inaltos, 
 fc of lato years 
 
 ixville, I'a., I 
 oin thus prc- 
 [) briiij;- before 
 ss for the ex- 
 , be found to 
 isod upon the 
 d and a solu- 
 iliiblc dichlo- 
 tlio form of 
 
 3 the subject of 
 es Douglas, Jr., 
 
 elilorliydiic ac' I, and the simiiltan is forinulion of Milphurie aeid, 
 
 as simply expressed in the old iiolalion by the formillu 
 •Jl'iiCl fS(),+ IK) Cii/'l »■ llci I so,. 
 The resiiltiiiM; aeid solution, wlieii broni,dit in eonlaet with i-iiprie 
 oxide, will take upas mneh eopper as it orijrinally held, which iiiav, 
 in its liiiii, be thrown down by siil|)huroiis acid. In this wav, the 
 solution of copper from an oxidized ore, and its precipitation as 
 dichloridc, may be repealed iiidelinitely, provid»«(l chlorine be sup- 
 plied each time by the addition of a siiilicient animint of some solu- 
 ble chloride. 
 
 The reaction between siilphnroiis acid and a .solution of prolo- 
 ehloride of copper goes on slowly at ordinary temperaliires. but is - 
 very rapid l>elween 80" and iiO'M'. Solutions of .sulphate of copper 
 mi.\ed with an e(piivaleiil of chloride of .sodium, and holdiiijr ,S.O per 
 cent, of eopper, after being treated at !)()^ V. with an excess of siil- 
 phiiroiis acid gas, retain less 1. per cent, of dissolved copper ; while 
 in the |)resence of an excess of sulphate of copper and sulpliiiroiis 
 acid the precipitation of the chlorine from chloride of .sodium is 
 nearly eomplele ; sulphate of soda and sulphuric acid remaining in 
 solution in acrordaiKu; with the eipiation 
 
 iiCuO.SOj + NiiCl + HO.^ .- Cu.CJ (• Nii,S()., t- L>S()., 
 
 The sulphnroii.s-acid gas for clfectiiig this reactio i a large scale 
 
 is readily got in siitlicicnt purity from the burning of iron-|)yriies in 
 the ordinary kilns used by the mak(!rs of sulphuric iicid, care bciii" 
 tliat an excess of .air be avoided. A Knowlos pump, constructed for 
 the purpo.se, has proved an eflieient means of injecting the heated 
 gas into the li(juid, JJy this reaction we have found it easy, in 
 repeated trials with a small experimental plant, to throw down in 
 three hours' time 125 pounds of copper from an eight per cent, .solu- 
 tifai, the lirjuid still retaining about one per cent, of coi)per diss(»lved. 
 Th(! acid liquors, when the reaction with sulphurous acid is com- 
 plete, have exchanged their bright blue color for a pale green, and 
 now contain in .solution an excess of sulphurous acid, which must 
 be got rid of bcf:>re using them to di.ssolve a fresh portion of copper. 
 This m;'y be effected by keeping back a small portion of the chlori- 
 dized copper-solution, and after the action of the gas is complete, as 
 may be known by the changed color and the sulphurous odor of the 
 liquid, adiling the reserved portion thereto, by which means the 
 excess of sulphurous acid will be oxidized. The chief part of the 
 dichloride of copper separates during the passage of the gas, but ii 
 further portion is deposited on the cooling of the solution. 
 
i 
 
 8 Tur, nYimoMi'/rAi.ii'ndY ni* roi-i'Kit. 
 
 'I'Ih' csccsh «)!■ «.iil|»liiirous uci<l may also hi' "fnt liil nl Uy lilowiiin 
 a ciirmit n{ Iml air lliroii^rli tlir lit|iii(l iil'ltr il lia- Imcm willi.lniwii 
 frniii till' |>nri|)ilalo<l dicliloridc, and Im'sI wliilii tin- i.ruccsH ol' sal 
 inatiiij,' it with oxidr (»rco|i|Hi' U \i^n\\\i nii. This, when not hy lln' 
 falciiialiiiii til" s;il|ihiirc'tt('d i»rcs, (•(.iilaiik.- m"»iv or Irss suhoxidi- ol 
 i'o|>|Hr,' which, with chloriiytlni! afi<l I'orms a |iorlinii of .•ii|.ri)ii> 
 I'hloi'idf, ami the separation of this, under these eir<iini-tani'e>. may 
 he prevente<l hy (he action of atmosplicric o.\y;icii. 
 
 ( nprous chloride isipiielxly transftrmed into i upricoxychloiide hy 
 atmosplicric oxyj^cn, and when dissolved or sns|ieiidcd in an acid 
 li(piid is hy this means readily converted into a cnprie sail, which 
 niay he a-rain rednced to cnprous chloride hy the action of snlphiirons 
 acid, ill this way, liUc the nitri.' oxide in llic leaden chaml«r. the 
 enproii> chhn'idc acts as a medium (liroii;;!! which >iiIplinroii> and 
 and oxy^^cn are made to eomhinc and to form sidplinrie acid. 'I'hc 
 two reactions of oxitlalion and reduction just dcscrihc<l may ;:•> on 
 alternately or simnltaneonsly in the li(jnid, and thus il happens thai 
 when an excess of air enters the pyritcs-Uiln, so that coiisidcralilc 
 frei! o.xvj^fcn passes with the snlphnrons acid into the coppcr-sohition, 
 the dichloride is either separated slowly or not al all, wildcat the 
 same time much sulphuric acid is iiirmcd. iJy lakiii-' advanta;;e of 
 these reactions hctweeno.\yij;en, snlphnrons acid, and chloride <if cop 
 per, we may al will increase the solvent power of onr acid hath. 
 
 In applying' this new process of eoppcr-e.xtraction to a roasted 
 sulphnretted ore uv matte, which we will suppose to contain a por 
 tion of silver, wo het>;in hy dissolvinj-' tli(>rciVom hy water the sul- 
 phate, which, with ])roper care in roastiii;--, should contain not less 
 than one-third of the copper of the ore; laUinj,' care to add to the 
 water enouj;h of some .soluhlo chloride to <'hloridi/e and render 
 insoluhle any sulphate of silver which may ho present. From the 
 clear lixivium thus ohtuined, after addinj!; the recpiisite amount of 
 chloride of sodium, the copper is precipitated, as already dcscrilied, 
 hy the action of suliihurous-aeid i^as. The resultinjr aeid Tuiuid, 
 freed from the excess of sulphurous acid hy the addition of a re- 
 served portion of the oriffinal solution containing copper-chloride, 
 and still rclainiu}:; more or less copper, is now used to dissolve the 
 oxide of copper from a portion of the lixiviated ore ; the process being 
 
 * 1 liiivc i'ounil uaU'inc'^l siiliihurotted CDiipor-oros to (.'(mtiiiii, in !nlilitii)ii to 
 sohililc ciipi'ii.' ^\ll^lllllt(', iiiul itisotiiblc oxidis of ('opiicr, ii siiudl iiortioii of ii 
 cuiiroiis coiiiijouikI, wliicli, tl)oiii;li iiisolubli! in water, is ilissolvi'il by ii hot iind 
 stroll" solution of coiinnoii suit, iinil is probiilily ii I'liproiis siil|iliat(! or siilpliito. 
 
Tin; iiYiii{nMi;rAi,i,i-'i!iiv or n»i>pi;ii. 
 
 
 
 III l)V lili)\viii;j 
 (I'll willidriiuii 
 iiruccss of sal 
 licii y(»l Ity iIk' 
 'ss siiliiixiilc III 
 [(III III' rll|ifiill> 
 liu<^tiiiii'f>, iiiiiy 
 
 (ixyclilniitic liy 
 lied ill ail acid 
 |iiic >all, wliii'li 
 II nrslll|)lllirnll> 
 II rliallllifl', tilt' 
 -iil|iliiirtius a< id 
 iii'i(! ai'id. 'lilt' 
 lied may j^k <>ii 
 it liappfiis llial 
 lal coiisidcralili' 
 i'(t|i|K'i'-Hiliitiini, 
 ;ill, wliilc at iIk' 
 ii;i' advaiitajii' ^^i' 
 cliloridc <il'n>|i 
 1' arid lialli. 
 nil III a roast I'd 
 ) contain a |)(>r- 
 V water tlic siil- 
 coiilain not less 
 ic to add to tlu' 
 li/e and nMidtT 
 out. Frouj (lie 
 ilsitc amouni of 
 ready dcscrilji'd, 
 injr acid rK{»id, 
 iddition of a iv- 
 coppcM'cliIoridc, 
 1 to dissolve the 
 the procesa beinj;' 
 
 4 
 
 aided liy liral, and, il'llii' I'ui'inaliMii of diclilnride ul' euppi r i> in Imi 
 ("ciirt'd, liy (lie iiijcelinii III' a riirniil of air, wliidi iiiiiv lie niadr iIm? 
 means of liealiiiir and a'^nlaliiiL^ tin' miMiiie. irilu' ore loniaiiH 
 silver, eiilicr ill the form of inelal or iiiiiisii|i/ri| «iilpliide, we have in 
 file ihloridr iifi'iipiiri' whirh i-liii'iiied I he III -t aneiil for lirin;;in^ il 
 to (he ei Midi I ion of eliloride III' -ilver. 'I'lii'^ will he foinid in the vol 
 <lne after the e\trii(lion of ihe eopper, inncihi'i' with any <iu\t\ which 
 may he pri'setit, lead as -iilphale, oxide.- of anlimony and iron, and 
 earthy matters, (ohalt, iiiekel, and /iiie, if present will, however, 
 he dissolved, and not hein^- precipitated hy siilplmrnii^ acid, will, l>v 
 Miu'('<'.«*Hiv(' operations, accumulate in the solntinii, .iiid may afterwards 
 he extracted.' l''rom tin' residue- thus deprived of coppci' we havo 
 found llie silver to lie readily dis-nKrd hv hriiie, I after which, if jjold 
 he present, it may he removed hy chlorinatioii, or the two preeioiis 
 metals may be extracted lotrefher from the loidiies hy amalt^amatiou. 
 When, as ill the case of eertain mattc-^ tVom I'tah, for exiunpic, tin; 
 residues eonfain a larj^e amount of lead as sulphate, this inav \n' 
 recovered hy smelting, and a hasi' hiillioii ;j,(»t contaiiiinu,' the precious 
 metals. The same result mav also he attained hv smeltiiiii' the re.s- 
 sidiies with an admixture of a lead-ore. 
 
 Chloride of silver is sohihle to simie extent in soliitiun of eiiprio 
 chloride, and is then in part carried down with the i-iiprous chloride 
 in the preci|»itatioii of the laiter. 'IMie formation of ciipric (;hlorid(! 
 may be avoided hy addinj^ to tlic solutioii of sulphate of copper 
 little more than the amount of chloride of sodium necessary for tlu* 
 oonversion of the copper into diehloride. In this case, as we havct 
 seen, the acid liipiid aft-'r precipitalion by snlplnirous acid will con- 
 tain ehielly sulphuric acid, tliou;j;li .still holdiiiL;' siillicient enpi'ic 
 chloride to eireet tlw; chlordizing of any silver which may be present 
 in the ore. 
 
 The difihloride of copper, as obtained hy precipitation, is a white 
 coarsely erystalline powder, having a npccific gravity of .").;}7() (I'lav- 
 liiir and Joule), and, as we have .seen (note on page I), is iiearlv 
 insoluble in cold water. After being washed from the acid licpiid, it 
 may be readily reduced by placing metallic iron in tlw? moist di- 
 ehloride, which should he covered with water to exclude the iiir. 
 The action spreads rapidly through the [irecipitate, so that a single 
 
 luiii. ill :iililitii>ii l<> 
 5iiii>ll iiortiuii 111' II 
 iiivi'il by It liiil iiml 
 Ifilmto or siilpliito. 
 
 * For ()li.«i«fviitio!is on tlu; iisHoi.'iiaion of r.iclicl ami I'uljiilt wiili ci:rUiin (iiiipnr- 
 orcs, sec Appuiidix J. 
 
 t for iKitus on tlu^ solubility "( I'lilorido ol' >ilvor in solulionn of I'oininon .-iiilt 
 and otlior chlorides, sue Apiicndix II. 
 
10 
 
 THE HYPROMETALIJTROY OF COPPEIl. 
 
 mass ol" iron will, in a lew hours, clianjio a considerable volume of 
 (lieliloride around it into pure spontry metallic copper. The reduc- 
 tion of copper from solutions obtained in those wet processes where 
 the copper exists as protochloride, often accompanied by salts of iron, 
 entails a considerable loss of metallic iron, and <jjives a (!op|)er which 
 is impure from the presence of basic iron-salts. The reduct'on of 
 the solid dichloride, however, presents none of tliese disadvantajfcs. 
 Forty-five parts of iron sufTu^e to reduce one hundred parts of cop- 
 per ; the j)recisc ratio being as 2(S.0:G3.4. Tiie ferrous chloride 
 which remains in solution may with advantage be used instead of 
 chloride of sodium lor chloridizing subsequent solutions of sulphate 
 of co|)per, ferrous sul[)hate being formed which, as it accumulates, 
 may be separated by crystallization from the acid liquid. The 
 ferrous dicldoride requireil to chloridize twenty i)arts of copper 
 would ecpial about sixty-one parts of hydrated ferrous sulphate. 
 
 Another mode of treating the dichloride, which may in some cases 
 be resorted to, consists in decomposing it, best at a boiling lieat, with 
 a slight excess of milk of lime. The dichloride is by this means 
 converted into a dense orange-red suboxide of copper which, after 
 being washed from chloride of calcium, in a filter-press or otherwise, 
 and dried, may be readily reduced to metallic copper in a reverbera- 
 tory furnace. For this reaction, 28.0 parts of pure quicklime are 
 required for G3.4 parts of copper, and the resulting chloride of cal- 
 cium may be used instead of chloride of sodium or chloride of iron 
 for chloridizing solutions of sulphate of copper. In this case, there 
 will be formed an insoluble snlj)hatc of lime or gypsum, while the 
 free sulphuric acid of the solution is re])laced by chlorhydric acid. 
 The use of the chloride of calcium wouki, however, require an addi- 
 tional operation, since, to avoid the presence of^the precipitated 
 gypsum cither with the dichloride or the undissolved residue of the 
 copper-ore, it would be necessary to add the chloride of calcium to 
 the clear copper-solution, and, after allowing time for the gypsum to 
 subside, to transfer the liquid to the vats in which the copper is to 
 be precipitated by sulphurous acid. There may, however, be local- 
 ities in which the cost both of metallic iron and of common salt is 
 such as to render advantageous the decomposition of the dichloride 
 of copper by lime, provided there is no silver to be extracted. 
 
 We have heretofore considered only the case in which the acid 
 liquor got by jirecijiitating the (fO]ij)cr from neutral solutions in the 
 form of dichloride is used to dissolve successive portions of oxide of 
 copper alone. This can be done in the case of pure ores free from 
 
TIIK IIVl)|«).MK'l'AI,I-irU(JV OK COPI'KIJ. 
 
 11 
 
 hie voluiiio of 
 . The roduc- 
 rocesst's where 
 y salts of iron, 
 
 (iopper wliifh 
 : re(hu't*oii of 
 lisadvanta}:;e8. 
 
 parts of cop- 
 rroiis chloride 
 scd instead of 
 lis of sulphate 
 t accumulates, 
 
 liquid. The 
 rts of copper 
 sulphate. 
 
 in some cases 
 ing heat, with 
 by this means 
 ir which, after 
 I or otherwise, 
 n a roverbera- 
 quicklime are 
 iloride of cal- 
 loride of iron 
 his case, there 
 urn, while the 
 orhydric acid, 
 juire an addi- 
 B precipitated 
 residue of the 
 of calcium to 
 he gypsum to 
 e copper is to 
 3ver, be local- 
 immon salt is 
 the dichloride 
 :tracted. 
 hich the acid 
 lutions in the 
 ns of oxide of 
 ores free from 
 
 other stntiigly basie oxides, if witlioiit loss, yet withoul any gain of 
 a('i<l save what comics incidentally from the portion of sulphuric 
 anhydride which is given olf in the calcination of pvritcs. or from 
 the reaction between sulphnrons iicid and oxygen in the presence of 
 chloride of copper, as already explained. If, however, as is more 
 often the case, we are treating artitieially oxidi/ed sulphuretted ores 
 or mattes, which yield by roasting a mixture of oxide and sulphate 
 of eopjier, it will be apparent that by the repeated use of the present 
 process there nuist result a constantly augmenting {iroportion of free 
 acid in tli(( licpiid. 
 
 This may bo made clearer by examples. F.et us suppose a solution 
 holding in a cubic foot (equal 1000 ounces of water) ().}.4 ounces or 
 two equivalents of copper in the ibrm of sulphate. To convert this 
 into protochloride would reijuire two equivalents or 117 ounces of 
 chloride of sodium, but i'n- the production of the dicihloride, as we 
 have seen, one equivalent, or a little more, will suflicc, or, in place 
 thereof, a corresponding amount of ferrous or calcic chloride. When, 
 by the action of sulphurous acid, the whole of the copper is reducecl 
 to the cuprous condition, and in a great part thrown down as di- 
 chloride, the previously neutral solution will contain two equivalents 
 or 98 ounces of sulphuric acid* (oil of vitriol), which, if a larger 
 amount of chloride had been added, would be in i)art rei)laced by 
 eh'orhydric acid. These two equivalents of acid are capable ol" 
 taking up two equivalents, or 79.4 ounces of oxide of copper, after 
 which the solution will contain, as at first, 63.4 ounces of copper. 
 If, however, we add to this acid solution, instead of simple oxide of 
 <;opper, a calcined ore or matte in which one-third of the copper is 
 present as soluble sulphate, and two-thirds as oxide, it is clear that 
 when the acid is saturated we shall have in the liquid, besides the 
 GbA ounces of copper from the oxide one-half as much more, or 
 31.7 ounces of copper which were already present as sulphate in 
 the roasted ore; making in all three equivalents or 95.1 ounces of 
 dissolved cop{)er, which are, in their turn, to be converted into 
 dichloride. Now, as the amount of acid set free in this reaction is 
 equal to that originally combined with the copi)er, it follows that 
 the liquid after the precipitation of the dichloride will contain three 
 
 * Whilo wo recognize tlie dyiid nature of oopjier, oxygen and sulphur, and 
 the l)il)asicity of suliiluiric acid, it is simpler and uiore oonvi.'nient for the enl- 
 culaiions of the manufaeturini,' elu'mist and the metallurgist to use, as wo have 
 done in tho present paper, the older notation, ami to speak of ai.7 parts of cop- 
 per, 8 parts of oxygen, 40 j.arts of sulphuric oxide, 40 parts of oil of vitriol, 3U.5 
 parts of chlorliydric acid, and 58.5 parts of chloride of sodiuu as e<iuivulents. 
 
12 
 
 iiiK iivi>I!()metai,i,uk(;y ok COrPEIJ. 
 
 'it 
 
 ?il 
 
 eqiiiviik'iits oi" acid, instead oi' I wo :is hcfdrc II' to this we add, a 
 second time, cnoiiiili of tlic mixture oi' (wo-tliirds oxide and one-tliird 
 sul|iliate oi' eo|)|ier to noiilralize tlies(> three equivalents, we shall 
 have I'our and a hali'ecjwivalents ofdissolved copper, i'roni which, hy 
 a third repetition oi' the ])i'oeess oC precipitation by sulphurous acid, 
 I'onr and a halt' e(piivalcnls of sulphuric acid woidd he set f Vc" ; so 
 that in place of !)8 ounces we should have 2'20\ ounces in the solu- 
 tion ; — an amount which a I'onrth repetition ol'thc process of satura- 
 tion and ])recipitation woidd raise to six and threo-(juartcr ccjuiva- 
 lents or ;>■"»(• ounces ol'oil of vitrol. 
 
 if, instead of a m i xt nre con tainin<:;one-third.of its copper as sulphate, 
 we have one in which only one-i'ourth is sulphate and three-fourths 
 are oxide, we should jict hy saturatinii: with this a solution con- 
 taining two equivalents oi' acid, and subsequent ])recipitatiou with 
 sulphurous acid, a licpiid holding' 2.G(! equivalents of free acid, 
 which by a thinl repetition of the process would yield -'i.or), and by 
 a fourth 4.73 e(|uivalents of free acid, in place of the 2.00 c(jui.valents 
 which were present after the fn-st precipitation. 
 
 The above calculations arc founded on the su])|)ositiou that the 
 roasted ore or matte contains, besides the oxide oi' copper, no base 
 that woidd be attacked by dilute acids. In tact, however, oxides of 
 lead; zinc and, n.iore rarely, nickel and cobalt, nuiy aceonq)any the 
 copper-oxide, and give rise, the first to an insoluble and the others 
 to soluble sidphatcs, consuming more or less acid. Ores containing 
 more or less carbonate of lime (oi'ten with carbonate of magnesia) 
 are also of frc<pient occurrence, and here is seen a great advantage 
 wdiich this mode of coppcr-exti-action |)ossesses over all the other 
 wet j)ro(^esscs; for since lime and magnesia, and their carbonates, not 
 only neutrali/e free acids, but throw down cop[»er from its solutions, 
 the treatment, by these processes, ol'ores containing any considerable 
 proportion of calcareous matter is iin])racticablc. With the process 
 here pro])osed, which generates an abinnlanee of free a<'id, the ex- 
 traction of coi)[»er from ores which do not contain an excessive 
 amount of calcareous matter pn^sents no diilie\dty except such as 
 arises from the mechanical obstacle <rcatcd by the ibrmation of 
 gypsum in the solutions. 'I'he accumulation of acid in the bath is 
 indeed so rapid in many cases that it will become unnecessarily 
 strong, and mav bedilulcd with water; while that portion not nee<led, 
 al'ter being deprived ol' the last portions of copjter by the action of 
 metallic iron, may be rejected unless it retains in solution other 
 metals of value. 
 
 it. 
 
TUF; IIYI)R()MKT.\F,I,UlHiY OF COI'I'KH. 
 
 13 
 
 this we add, a 
 (■ iiiid oiic-tliird 
 il('ii)s, we slmll 
 iVom wliicli, l)v 
 dpIiiu'DUs acid, 
 1)0 sot fre" ; so 
 ■OS in llio solu- 
 (icoss of satiira- 
 juaitor o(jiiiva- 
 
 il)ora8sul|)liato, 
 (1 tliroe-tburtlis 
 I solution oon- 
 >oi|)itation with 
 < of froo aoid, 
 d •i.i)i'), and by 
 .00 C(jiiivalonts 
 
 sition that iho 
 'oppor, no haso 
 over, oxidos of 
 ao'onipany tho 
 and tlio othoi's 
 )ros oontainin"' 
 
 of niaj>;nosia) 
 •oat advantago 
 r all tlip othoi" 
 oarbonatos, not 
 111 its solutions, 
 [\y oonsidorablo 
 
 ith tho process 
 !0 acid, the ox- 
 
 1 an oxcossivo 
 [•xcopt such as 
 ! (brniation of 
 
 in tho bath is 
 ; nnnocossarily 
 ion not noodod, 
 y tho action of 
 sohitiou otiior 
 
 I 
 
 Ft will bo soon from iho ("orogoiiig description that tho now process 
 here dosoribod rosembles those which, at tho beginning of this paper, 
 wo have placed in Class If, inasmuch as the oxidi/od copper is sepa- 
 rated from foreign metals by dissolving it in sulphuric and chlorhy- 
 dric acids; with tho diilorenoo, however, that tho icids tor this pur- 
 pose are gonoratod in the process itself, by the action of sulphurous 
 acid, while tho copper is separated from its solutions in the form of 
 diehlorid(v, the reduction of which to pure copper is readily en'octed 
 by the consumption of a minimum amount of metallic iron. At the 
 same time, any silver or gold whieli may bo present in tho ore is left 
 undissolved, and in tho best (condition fi)r subsequent extraction by 
 well known methods, while the saving of cobalt and nickel, of load, 
 or of antimony, should these bo ])resont in quantities of economic im- 
 portance, may be subsequently oirecte(i by very simple processes. 
 
 Tho apjiaratus for this new general method of copper-extraction is 
 simple and inexpensive. The chlorine re(juire(l in the precipitation 
 of the copper being rc(!0vered tor further use, the only reagent con- 
 sumed, except the sulphurous aoid — which is a waste j)roduot 
 from the roasting of sulphurous ores — is an amount of iron which is 
 equal to less than one-half the weight of tho copper, and may be 
 recovered in the form of sulphate of iron, — or, instead thereof, the 
 same quantity of caustic lime.* 
 
 Appendix I. 
 
 Tho presence of small portions of cobalt and nickel in cupri- 
 ferous pyrites is not uncommon, and mixed earthy oxides of copper, 
 nickel, and cobalt have been found in considerable (piantitios in ^[is- 
 .souri. A greenish, translucent, amorphous niin«>ral, with black 
 stains, resembling chrysocolla in appearance, from some place in 
 western Xovada, where it was said to be abundant, and to have 
 been mined tor the manufiicture of sulphate of (Mtppor, was brought 
 to mo in 187(5, and found to contain considerable <|uantities of both 
 cobalt and nickel. One of two closely agreeing analyses by my 
 tbrmer pmiil, Mr. Ilardman, made at tho Mass. Institute of Tech- 
 nology, in 1877, gave for this mineral as follows: ()xi<le of co|)per, 
 1>.G.'3 ; oxide of nickel, .'5.2.'} ; oxide of cobalt, 3.88 ; |)oroxide of iron, 
 3.08; peroxide of manganese, 2.-10; lime, 1.01; magnesia, 0.10; 
 
 * United Stiitc* lctlt'rs-])iitcnt, No. '2'2'i,'M)2, I'.n' lliis iiii'tliod oC ici|i|iiT-i'xtni(;- 
 tion wore y run tud to Thuiniis Slurry Hunt und Jumes Douglus, .Jr., Miiy L'Slh 
 1880. 
 
14 
 
 Tin; llYDUOMKTArJAJItOY OK COl'PKK. 
 
 aliiiniiiii, i;i.01 ; silica, 42.97; walor, 1.S.38 =-^ {>7.72. The cobalt 
 and nickel wm; separated l)y Itose's niethod. Another analysis, in 
 wliieli tliese metals were sei)anited hy the met hod of Fischer, with 
 nitrite of potassinni, yave of oxide ol'eohalt, 4.11. Snch an ore, if 
 iibnndant, wonid be a valnable soiinte of b(»lh nickel and eol>alt. 
 
 This alnnunons mineral, like chrysoeoUa {ante, page 2) is attacked 
 by a solntion of ferrous chloride and (!onnnon salt, by which the oxides 
 of cobalt and nickel are indirectly <lissolved ; since, althoufrh they 
 have not the |)ower of decomposinjj; ferrous chloride, they decom- 
 pose the cupric chloride which is tbrmed by its reaction with cuprie 
 oxide. 
 
 Al'PKNDIX If. 
 
 As regards the solubility of chloride of silver in solutions of chlo- 
 ride of sodium, Vogel found that one liter of a saturated solution, at 
 ordinary temperatures, lield dissolved ().l»50 grams of chloride of 
 silver, while according to llahn, a liter at 19.6" C. holds 1.269 
 grams. IJeccpiercl ibund at ordinary temperatures for a similar 
 solntion 0.800 grams to the liter. 100 parts of water, saturated at 
 100° ('., hold 26.61 parts, and at 15.6" C, 26.34 parts of chloride 
 of sodium, the densities of the solutions being respectively 1206.93 
 and 1204.03. Hence, one liter of a saturated solntion at 15,6" 
 holds 316 grams of common salt, 1000 parts of which solution 
 under these conditions dissolve, according to llahn, at 15.6° C, 3.0 
 parts of chloride of silver; while, according to the observations of 
 Vogel and of Becqnerel, at "ordinary temperatures," not defined, 
 1000 [)arUs, in saturated solution, dissolve respectively 4.0 i)arts and 
 2.53 parts ol' chloride of silver. The latter figure approximates to 
 that given by Pelouze and Fremy, according to whom 1000 parts of 
 salt at 18" C. hold dissolved 2.40 i)arts of chloride of silver. The 
 solvent power, according to these chemists, varies greatly with the 
 temperature, the amount dissolved being equal to 1.70 parts at 10° 
 C, and not less than 6.80 at 100° C, while at 0" C. but traces of 
 chloride of silver are dissolved. Differences of temi)erature may 
 suffice to explain the discrepancies between the results of Vogel, 
 llahn, and JJecquercl, but not those of Pelouze and Fremy at 18.0° 
 C, a temperature above that mentioned by llahn, It is possible 
 that these chemists may not have emiiloyed solutions saturated with 
 chloride of sodium, to which the observations of the others refer. 
 Fresenins, speaking of the solubility of chloride of silver in hot 
 concentrated solutions of the chlorides of sodium, potassium, am- 
 
 •il 
 
THE HYDROMirrALMTROY OF COPI'KIl. 
 
 16 
 
 '2. Tlip cobalt 
 Mer aimIy.siH, in 
 >r Fischer, with 
 Siicli an ore, if 
 I and c()l>alt. 
 ire 2) is attacked 
 ,viiich the oxides 
 ', althoiiffh they 
 th", tiiey deeoni- 
 tion with cuprio 
 
 ohitions of'chlo- 
 ated solution, at 
 s of chloride of 
 
 C. holds 1.269 
 !s for a similar 
 iter, saturated at 
 tarts of chloride 
 L'ctivoly 1200.93 
 (lution at 15.6^ 
 
 which solution 
 
 at 15.G° C.,3.() 
 
 observations of 
 L's," not defined, 
 ily 4.0 [)arts and 
 approximates to 
 im 1000 parts of 
 
 of silver. The 
 greatly with the 
 .70 parts at 10° 
 C. but traces of 
 emi)erature may 
 ,'sults of Vogel, 
 
 Fremy at 18.0° 
 
 It is possible 
 
 IS saturated with 
 
 the others refer. 
 
 of silver in hot 
 
 potassium, am- 
 
 monium, calcium, zinc, etc., says "On sMllicicnt dilution with cold 
 water the dissolv<'d portion separates so completely that the liltratc 
 is not colored by suljthuretted hydrogen."" 
 
 An to the solubility of chloride of silver in some other chlorides, 
 riahn foinnl that a liter holding .'>(). 70 per cent, of ferrous chloride, 
 and having a specific gravity of 1.119, dissolves, at 20' ('., 2.38;") 
 grams of chloride of silver ; while a solution, holding 14. IS per cent, of 
 cupric chloride, and having a specific gravity of 1.5720, dissolves at 
 30° C, for 1 liter, O..S30 grains of clilori<lc of silver. For farther 
 observations on the solubility of chloride of silver in other chlorides, 
 sec I'ercy, MditUurijn of Si/rcr mul (laid, J'art I, p. oS, and also 
 Malm, Traimaviions Avirrican Imlilutc Minimj J'Jni/iiun;^, Vol. II, 
 p. 99. 
 
 * Frescnius, Quanlilativi^ Atmlysis, .Amor. Kd., IS'O, p. 124. 
 
^J