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I
[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