1000000030

H E

t.!,;s

~!k\,

renom it ii1uch more foliJ,

~nd

Ihe mixed

n",fs

co~,inues

tolerably ou8ile.

If, on the

C(lntr~ry,

tO one pm of tin len pans of

corper ue . dded, togelher wilh

lillle zine, a femi–

mml tO be conr"lered hereafter, fromthi9 eomuination

there refults _metdllinecompound, which is hard, brillle,

an,1 rel )' fonorou9 ; fo

th~1

il is ufed for caning bell, :

This compor,tion is called

hro,m

~nd

hdl-nutal.

Tin h.t h an affinilY with the vitriolie, nitrous, and

marine acids. AII of them

att~ck ~nd

eorrade it; yet

none of themis .ble to dilfolve it without great dilliculty :

So that il a clear ((¡Julion thereof ue delired, particular

melhnJs 01,,11 be en;ployed for that purpofe; for the a–

cids do uUt in •

m~nner c~lcine

it, and conven it to a

kind of whiteealx or precipilale. The folvenl whieh has

Ihe gre"en power over il is

nqua rrgil,

whieh has even

~reater

.fIinilY Iherewid, Ihan wilh gold itfelf; whence

il folloll's, thal gol<l dilfoil'ed in

aqua rrgil

may be pre–

cipitated by mean' of tin ; bUI Ihen Ihe

a1"a rrgil

mull

~'e~kencd .

Golrl Ihus precipilatcd uy lin is o( amoll

bcaulifu l eolour, and is ufed for a red in enamelling and

p;<inting onpo.celain, as alfo ro give a red eolour 10 ar–

tificial

g~ms.

lf Ihe

"qua rrgil

be not 10\Vered, Ihe pre–

e.pitm will not

h~ve

the purple eolour.

Tin halh Ihe propclly of givinH a greal lullre to all

red eofou!'s in geoeral ; I,n whieh aceounl il is ufed by

the d)'ers for Ilriking a bealltiful fcarlet, and lin·velfels

;¡re emplo)'cd in makiog

~oe

fyrup of violels. Water

does not a8 upon this mml, as il does upon iron and

copper; for which reafon it is not fubjel! tOrull : ne–

\'<:.

Ihelcfl, when il is expofeJ 10 the air, in furrace foon

lofts its poiin, and fpl endor.

Tin miKcd with nitrc, and expofcd to tbe Gre, deAa–

gmes with il, makes il delonate, and is

immedi~ldy

conremd 10 a

re[raflor! cah;

(or f9

~II

fubllances are

called which

~re

incapable of fufion.

Tin readil)' unites with fulphur, and with it becomes

a brinle and friable mafs.

Of LEAO.

N EXT

to gold and mercllry, lead iS 1he hcaviell of alJ

me:alhne fubllances, bUI in hardnefs is exceeded by e·

very one .o( them. Of all mm ls alfo it melts the

e~fiell,

excepl tin o While it is in fufion Ihere gathers incelfant-

1)' on its furface, as on Ihal of tin, a blackilh, dully pel.

1~le ,

whieh is nOlhing bllt a calx of Icad.

This calx fu nher ealcined by a

moder~te

fire, the

llame being reverberaled on il, foon gro\Vs white. lf

the e. lcinalion be eontinued it becomes yellow, and al

tan of a beautiful red. In Ihis

it is called

Ininilllll,

a~d

i! ufed as

pigment.

Mi"i/llll

is nOI rafily made,

3nd Ihe opcralion fueeeeds \VeU in large manu(aaures

aoly.

To eonven lead inlo

litharge,

which is the metal in

m~nner

half vilrified , you neeJ only keep it mdlcd by

a prcoy flrong fire; (or Ihen, as ils

furf.ce

gradtlally

calcines, il teods more and more to fufiQJI and vitrifi–

ealion.

Alllhefe preparalion! of lead are gready difpofed 10

pr.r(e{\ (lIr,on

~nd

vilrification , and

thal pllrpofe re–

~1Iire

bUI a

m~derJlc

desreeof fire

Ihe calx or eanh of

Ic~d

being of a11metalline earthl thal which .ítrifies the

muO eafily.

Lc~d

hath not only the propeny of turning ioto glafs

wilh the grealdl

f~cilily,

bUI it

h~lh

alfo Ihal of pro–

mOling gready lhe vitrir,mion of

~II

Ihe other imperfelt

mm ls ;

~nd,

when it is aallally vitrified, procures the

ready (ufion of all eanhs and Ilones in general, eventhofe

which are rcfraaory, thal i" whieh cOllld not be fufed

withoul ils help.

Glafs of lead, befides its

gre~1

(ufibility, hath alfo the

fingular property o( being fo fubtile and aaive

tO cor–

rode and penetrate theerucibles in which it is meherl, IIn–

lefs theybe o( an emh thal is exceeding

h~rd,

comp.a,

and wilhal ve'ry re(raaory: for glafs o( lead being one of

the mol! pOlVerftll Auxes that \Ve know, if the eanh of

the erucible in which it is mclted be in Ihe fmallell de–

gree (ufible, il will be immed.ately ,ilrified; efpecially

there be 30y metallic maller inils eompofitioo.

The great aaivily o( glafs o( lead may ue weakcned

by joining il with olher vitriliable maners

but unlefs

thcfC be

~dded

in a very grea! propottion, it will f1ill

rem~in

power(ulenough tO penetrale eommon eanhs, and

carry olf the matters combined with it.

I~efe

properties of lead, and of the glafs of lead,

depends the whole bur,nefs of refining gold and filver. le.

halh beenAlewn, that as Ihefe t\Vo mm ls

~re

indellruai–

ble by fire,

~nd

Ihe only ones which

h~ve

tlm advantage,

Ihey may ue feparated from the imperfea metals, when

mixr.d therewith , by expofing the eompound tOa degree

o( fire C,tfficicndy l\rong to .vilrifyIhe

I~ttcr ;

which \Vben

once convened into

gl.fs

e_n no longer remain united

with any metal .tool has its mm lline forro. BUI it is

very difficult tO procure thlS vitrification of Ihe imperfeB:

melals, when uniteo with gold and filver : nay, il is in a

manner imponible 10 \'itrify them entirely, for two rea–

fons : firll, becaufe moll of them are

natur~lIy

very dif–

ficult to vitrify: fecondly, beeaufe Ihe union Ihey hal'e

eoom8ed \Vith Ihe per(ea mm ls de(ends them, in a

m~nner,

fr.cm

the aaion o( the fire,

~nd

Ihat fo much

the more elfcaually as the proportion of Ihe perfe8 me–

tals is greater; \Vhich being indeflruaible, ¡nd in fome

fOf! coatine over thofe \Vilh which they

~re

,Jloyed, fen'e

themar

prefervative ¡nd impeoctrable Ihield againll the

ulmofl violrnce of

fir~.

is ¡hm(ore clear, that a greal deal of labour mayhe

favéd, and that gold

~nd

film may be refined to a much

greater degree of purily than can otherwife be outained,

if 10 a mixlure of thefe

mel~ls

\Vith eopper, for innance,

or any olher imperfea melal, be

~dded

a ecrtain quantity

le~(L

for Ihe lead, by ils known property, will in–

fallibly produce the dcr,red virrific3lion; and as il like–

wifeincreaf" Ihe proportion of Ihe i"'perfeft

met~ls, ~nd

fo lenens

th~t

of Ihe perfc8 melals, in Ihe mars, it evi–

dentlydeprioes the farmer of a pan of their

~uard.

and

fo effc8s

more cnmplete vitrificadon. lis the glafs of

lead halh the property of runOlng through the crucible,

~nrl

carrying \Vllh il Ihe nliltlc!'s \Vhieh il

h~s

vilrified,

it follo\Vs, Ih, t whenIhe vitrir,wion of the imperfea me–

tals is effeélerl by its me.lnl,' ,11 Ihofe vitrifi<d matters–

logethcr penelralc the velrcl conlaining Ihe fufed

mC1~I

linc mafs, difappm, and leave onlrthe gold and

~Iv.er

pel

fdU