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13 6 e H E M
To exl,afl Leod [rollZ il/ O,e.
HAVI NG roaned your lead·ore, reduce it tO a fine
powder i mix it with twice its weight of the black flux,
and ooe founh of its weight of cleao iroo filings and bo·
faX i put the whole into a crucible capable of cootaining
at kall thrice' as much i over aII put fea·falt four fin·
gers thick i cover the crucible i lute the juuélure i dry
the whole with a gentle hm, and fet it in a melting
furn ace.
Make the crucible moderately red: yon wiII hm the
fea·falt decrepitate, and after the decrepitatioo a fmall
hiffing io the crucible. Keep up the fame degree of fire
lill thu be over. .
Then throw io as many coals as are necelfary to como
plete the operatioo enlirely, and raife the fire fuddenly,
fo as to bring the whole mixture iOlO perfeél fufioo.
Keep up this degree of fire for a quaner of an hour,
which is time fullicient for the precipitation of the re–
gulus.
When the operation is finifhed, which may be known
~y the quielOefs of the matter in the crucible, and by a
bright vivid Rame thal will rife from il, take the crucible
out of the furnace, and feparate the regulus from the
{coria.
To[ep.rate [rol» Copper.
WITH lutiog earth aod charcoal·dun make aRat velfel,
widening upwards, and large eoough to contaio your me·
lalIine mafs. Set it fhelving dowowards from the back
lowards the lore·pan; and in the fore.pan, at the boto
10m, make a iittle guuer communicating with another
velfcl of the fame nature, placed near the former aod a
liule lower. Let the m0uth of the gutter withiafide
Ihe upper velfel be oarrowed, by means of a fmall iroo
plate 6xed acrofs it, while the loam is yet foft ; fo as to
leaye a very fmall appennre in the lower pan of this ca·
oal fufficient to difcharge the lead as it melIS. Dry the
whole by placiog lighted coals rouod it.
When this apparatus il dry, put your mixed mafs of
copper and lead ioto the upper velfel: hoth in that, and
in tlle other.velfel, light a my geotle 6re of wood or
charcoal, fo as not to exceed the degree of hm necelfa–
ry tO melt lead. lo Iuch a c!egree of heat the lead con–
lamed io the mixed mafs wiII melt, aod you IVill fee it
TUO out of the upper velfel ioto the lower i at the boto
tom of which it will uoite into a regulus. Wheo io this
degree of heat DO mGre lead BAw!, iocreafe the fire a
Jiule, fo as tO make the velfel moderately red.
Wheo no more 'ViII ruo, colleé! the lead contaioed
iD the lower velfel. Melt it over agaio io an iroo ladle,
with a degree of 6re fufficient 10 make the ladle red i
Ihrow ioto it a liule tallow or pitch, aod while it buros
keep nirriog !he metal, io order tOreduce 10y part of it
Ihat mly he calcioed. Remove the pelIicle or thio crull
which will form 00 Ihe furface i fquccze out all the lead
it contaios, and then put it to the mar! of copper left io
Ihe upper velfel. Check the 6re, and in the fame mano
Der take of!' a fecond Ikin tbat wiII form 00 the furface
of!he lead. LanIy, when the mml is ready to fix,
take off the lkio tlJat wiH tlJeo appm 00 it. The lcad
s T R Y.
remaining after this will be very pure, anJ free from aH
alloy of copper.
Wilh regard to lhe copper ¡tfelf, you will fiod it in
the upper velfcl co,ered with a thin coat of lead, and if
tbe lead mixed with it was in the propon ion of a founh
or a fi[lh par! only, aod the fire applied was geotle aod
flow, it will relaio nearly Ihe fame form after the opera.
tioo that the mixed mafs had before.
'fhe Calcina/ion o[ Lead.
TAKE what quantity of lead you pleafe; melt it in
ooe Or more unglazed eartheo p:tns : a dark grey powder
will be fouod on its furface. Keep nirring Ihe metal io.
celfantly till it be wholly cooverted ioto fuch a powder,
which is lhe calx if lead.
lo thecalcinatioo of all mml!, aod pmicularly in tbis
of lead, there appears a fingular pheoomenon which is
no. eafily accouoted foro lt i! this: though'thefe mat–
ters lofe a great deal of their fubnance, eilher by the
diffipation of their phloginon, or becaufe fome of the
mm l perhaps exhales in rapours, yet, wheo the cal.
cination is orer, tbeir calxes are found to be encreafed
in weight, aild this increafe i! very confiderable. AD
huodred pounds of Icad, for example, cooverted ioto mi–
nium, which is oothing but a calx of lead brought to ¡
red colour by cootinuing the calcioatioo, are fouod to
gaio len pounds weigbt; fo that for an hundred pounds
of lead we have one hUDdred and teo pouods of mioium :
a prodigious and almol! incredible augmentation, if it be
coofidmd tha" far fromadding any thing to tbe lead,
we have 00 the cuotrary diffipated pan of it.
Toprep." .[ L(od.
T AK E IWO parts of litharge, aod one parl of pure
cryllalline fand; mingle tbem together as exaé!ly as pof–
fible, adding a little nitre and fea·falt : pUt this mixture
io,o a crucible of Ihe mol! folid aod mol! compaé! eanh.
Shut the crucible IVilh a cover that may perfeélly clofe il.
Set the crucible thus prepared in a mehiog furnace ;
611 the furnace with coals i IIght thé 6re gradually, fo
tbat the ",hole may be Oowly heated : Then raife the
fire fo as to make the crucible very red, and bring the
mallel' it cootains ioto fufion; keep it thu! melted for a
quantr of ao hour.
Then lake the crucible out of the furnace, and break
it: lo tpe bOllom tbereof you will mon commooly 6nd
a fmall bUllon of lead, and over il a traofpareDt glaIs of
a yellow colour oearly refemhliog that of amber. Se·
parate this glaIs from the lillle bulton of melal, aod
froOl the falioe matters which you will fiod above it.
L,ad dijolved by /he Nilrm Acij.
P UT ioto a matras fome .qua [or/h precipilaled like
that ufed to dilfolve .filver i weakeo it by mixiog Ihere–
with ao equal quanúty of commOD water i fet the ma–
tras io a hot faod·hath i throlV ioto il, lillle hy linle,
fmall bits of lead, till you fee lhat no more will dilfolve.
Aqua [o,li/ tbus lowmd will dilfolve about a fdlmb of
its weight of lead.
There is gradually formed upoo the lead, as it dif.
folves, Dril a grey powder, aod aftcrwards awhite crun,
whicn