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'~ntagcs i fueh as makinR lhem harder, and leCs fuhjcD
lOlofe lheir dutlilllY, This may probably arife Irom
htncc, thallhe dnttililY of copper has lhe pcculiarilY o(
refilling 01011 of thole caufes which rob the 1,«reD me·
u1s of lheirs.
The property which olher mel~lIinc fuhn.nct's have in
eomOlon Wilh copper, of lufing lhe phlugliluo by eaki·
ning ami lheo vilrifring, furniOles us with a mcdlOd of
fepmling lhem from ~old and fih'cr, when lhey are
combined therewith. NOlhing more is required lh,n 10
eopuft lhe mafs, eompouOllcd of Ihe perfc<'l melals .nd
olher mmlline fubllAnces, lOa degrce of heal fu/li cieol
10 calcine whalc'er is 001 eilher gold or fih·rr. It is
evidenl lhal by Ihis mCAOS IheCe tu'Ometals will be ob·
tained as pure as is poflible; for, as halh already beeo
faid, no mmlline calx or glafs is capable of uniling "illt
melals polfelfed of lheir phloginoo. On Ihis principie is
formed lhe whole bufinef, of refioing gold and filver.
When lhe perfeé! melals have no other alloy bUI copo
per, as rhis melal is nOI lO be calcined Or vilrified u'irh·
our grear difficullY, which is incmfed by il! unioo wilh
lhe unvirrirrable melals, il is eafy 10 fee rhar il is almon
impoOible lO fe parale rhem WilhoUl addiog {omelhing 10
facilitate lhe vilrificatioo of rhe copper. Such metals as
ha,'elhe property of lurnlOg cafily 10 gla{s are "ery lir for
Ihis purpo{e; .nd ir is necelf.,y lOadd a ccrrain quanlily
Ihereof, when gold or filver is 10 be purified from the
alloy of copper. We {hall hafe oecafion 10 be mure
particular 00 lhis ¡¡lbjeé! wheo we come 10 lreal of lead.
Copper is foluble io ¡/I rhe aeids, Iu which il commu·
nicales a green colour, and fomelimes a blue. E,'cn lhe
neulral {alts, and water il{elf, aD upoo this mm/. Wllh
regard to waler indwl, as lite procuring il ab{olurely
pure and free from .ny {aline mixture is nexI lO an im·
poflibilily, it remains a queOion, whether lhe effeD it
produces on copper be not owing lO cenain faline parli.
eles conlained in it. lt is Ihis grear faciliry of being die·
folved lhat rendees copper fo {ubjeD to ruO; which is
nOlhing e/fe bUl fome pans of its furface corroded by
{.Iine parlicles cont.ined in lhe {urrounding air and
warer.
Tite rull o( copper is always green or blue, or of a
colour berween thefe IWO. Internally ufed il is very
noxious, being a real poifon, as are al/ the {olulions of
lhis metal made by any acid whalever. Thc blue co·
lour, which copper conOantly alrumes, when corroded by
any ¡aline fublfance, i, a Cure fign by whiclt ir may be
difcovered wher.·ever il ex,lIs, even in a very {mall
quanlity.
Copper dilfolved in lhe vitriolic acid forms a kind of
metal/me faft, which {hoOlS into rhomboidal crylbls of a
moti beauriful blue colour. Th& cryllals art eall.d
bit" vitriol, or vitriol o[ ca/'Per. Tltey are fometimcs
found ready {ormed in lhe bowels of lite emh; ami
m.y be arrificially maJe hy Jilrolving copper in the vilri·
o"c .cid: but lhe {olution will nOl Inccccd unler, rhea·
cid he wdl del'hlcgmaled. The talle (lf lhl' ,itriol is
{altiOl and allringenl. !t relains a conlid,,"ble qu.nlily
of waler in eryll.llizing, o.n whi~.h account il is e~lily
renclered Ouid hy fire.
It mnll beo~{cn"CJ, thal wlten it is eXl,ofed 10 a eer'
VoL. !l. No. 33.
s T n Y. 81
lain degree of hcat in ordcr to free il of ilS humirlity, ,
greal pm of il! acid aies olf .t lhe fanle time: Ami
hence il is rhal, a{ler cakinalion, there rem~inl only a
kind of earth, or mml/ine calx, Of .1 red colonr. wluch
contains bUI vcry linle acid. Th. c.nnO! be
brooght ro OowbUI WiUl lhe grwen diOiculty.
A folution of copper in lhe nltrous acid fonlts a {alr
w"ich does not cr)'/tal/ize, bUl, wh:n r¡etl, powerfully
attratls rhe moiOure of the airo The {ame lhing hap·
pens when il is diffoh'ed 10 lhe fpiril of {,¡JI, or In .'qua
"git.
If lhe copper, thus diffoh'ed by ,ny of Ihefe acids,
he precipiwcd by an earth or an alblt, il retains nmly
lhe col"ur it had in rhe folu tion: BUl thefe precipilates
are fcarce any lhing more lhan lhe earth of copper, or
coppcr of mofl of its phlogillon ; {o rhat if they
were expofed 10 a violenl fire, withoul any additamenr,
a gre.t par! of lit, m would be convemd 1010 an emh
Ihal could ne,er be reduccd ro a metalllne formo There–
fore, when IVe intentllo reduce thefe prccipilales 10 cop·
per, il is necelfary tO add acenain quanlity of afubOance
capable of reOoring lO lhem the phlogiOon they have 100.
The fubllance which halh becn found fimll for fueh
redué!ions is charcoal dnO i bmu{e durcoal is nothing
bur a phlogiOon clofely combined wilh an earth, which
render. it excccdingly hed, and capable of refiOing a
violenr fnrce of lire. BUI as Gharco.1 will nur meh, and
confeqnently is capable of preventing rallter than foro
warding the flux of a melal/ine calx or gla{s, which ne–
verthelefs is effentially necelfary lO complete lhe «due·
lion, ir h'lh been contrivt'd lO mix il, or any other rubo
llanee conlaining lhe phlogillon, with fuch fixed alkalis
as e~fily Oow, and are fit lO promote lhe Oux of other
bodies. The{e mixlures are called rdltcing jlltxa ; be·
cau{e lhe general naOle of Ouxes is gi\'en lO all {.hs, or
miXlures of falts, ",hich facilitale fufion.
lf fulfhur beapplied 10correr m3de perfe,qly red hor,
lhe mml irnmedimly runs i and lhefe two fubOances
uniting, forma new compound much more fufible lhau
pure copper. .
Thi. compound is dcOroycd by lhe fole force of fi re,
for t\Vo reafons: The firOis, lhal, fulphur being vola·
lile, the fire is capable of fubliming a great part of il,
efpeci.llly when il is in a great proportion lO lhe cnpper
Wilh which il is joined i lhe fccond is, lhat the portion
of fulpltu r "hich remains, belDg Rlore intimately unitell
Wilh lhe copper, Ihough il be rcndmd Ic{s CDrtlhullible
by th:u union, is nc,whelefs burnl and eon{umed in
lime. Copper b~ing combinctl Willt fulphur, and roge·
lher wilh il expofed tO lhe force of fire, is foun,110 be
pmly chAnged into a blue vilnol; becaufe the l"itriulic
acid, being difcngaged by burniog rhe fulphur, is by
lhat m~ans ~ualified lO difolve lhe copper. 111e allinily
of copper wi'h lulphur is gealcr lhan thal of lilver.
Thi~ melal, as wcll as the orher impcrfelq mctal~ .lnd lhe
{cmi·mmls, being minglcrl "ilh niue and exp"ferllO the
fire, is dccompofed ami calcinerl mllch fuoncr by it·
fdr: hcr.allfc the phlogiOon w~ich il cunt:tins tlce.llioos
lhe d, ll.'gration of the nitre. .IOJ confcquentl y the lItO
fllbllances mlllllally "ccllrnpl\f~ raeh olher. Thcrc are
eenain metalllOe {UbO.llW ",ho{e phlos,lIon is fu alo.lll·
t X tlant,