119 / 1042
100
e
H
E
M
tions;
~nd p~rticul~rly
by fubliming il (rom abforbrnt
tarrhs, which readil)' drink up oils. This is called Ihe
"flijic.lio"
of a volatile alk',I.. The fall, which before
was of a yellowith or dirry co:our, by beiog Ibus reéli·
ficd, becolllcs ver)' \Vhile, ami acquires an ouour more
rungent and Icfs fctid than il had al firO, Ihal is, when
obrainecl by one fingle diOillalion from apurrid fu bOance.
Ir
is proper looblen e, that Ihe redifi calion of a vo·
Jalile
alk~li
mull not be carried tOO far, or repeated 100
oftcn; for by that means il mal' be enlirely decompofed
at lenglh; ar.u particularly if an abtorbeut earrh, and
cfpeci.lly
ch.lk, be employed for Ihar purpofe, Ihe fall
mal' be convmed inlo an oil, an earrh, and water.
Volaril. alk.dis aél upon femal mcrallic fubllances,
Rnd parricularly on coppcr; of which Ihey rnake a mofl
bWlli ful blue folulion. On Ihis propeny depends a
pretty fingular e!feél, which happens fometillles when we
•uernpl by m"ans of a vplatile alkali 10 feparale copper
from an acid wilh whieh it is combined. InOcad 01 fee·
ing Ihe liquor grow rurhid, and Ihe mC(al fall, both
which generally happen whenany alkali whatever is Ipix.
ed wiro a metallic follllion, lOe are furprifcd
10
obterve
rhe follltion of copper, upon adding a volalile alkali, re ·
tain il¡ limpidity, and Iel fall no
precipitat~ :
or at leal!
if the liquor does grow turbid, il remains fo bUI for
a
moment, anel inflandy recorers ils Iranfrarency. This
is omlioned by adding fuch a quantity of volalile ,Ikali
A9
is more Ihan fu(!icient ful1y to f.'lurale Ihe acid of the
felulion, and confiderablc enollgh tO dilfolve al! the copo
per as faO as il is feparaled from Ihe acid. On Ihis oc·
tafioo tbe liquor requires a deeper blue Ihan it had be·
fore
j
which arifes from the rropeny which volalile alkalis
have of giving this meral, \Vhen combined \Vilh Ihem, a
["lIer blue Ihan aoy orher folvenl can: Hence we have
a touchOone 10 difcover copper \Vhere·ever it is ; for, let
the quanlily of this meral, combined with other merals,
b"
ever fo fmall, a volalile alkali never fails 10 difcover
il. hy makiog it appear of a blue colour.
Though a volatile a!kali be conOantly the refult of
putrer.aion, yel il mua nol Iherefore be imagined, thal
nore cJn be produced by any other means; on Ihe conlrary,
moll of thofe which contain Ihe ingredients necelfary to
form il, yield no ineonfiderable quanrily thereof in di·
Oillation. Tartar, for examrle, which by being burnt
in an open 6re is conl'trted, as was filelVn, ioto a oxed
alkali, yields a volallle alkali \Vhen il is decompofed io
cIofe v· lfels; Ihat is, when it is diOilled: Bec,ufe¡ in
Ihis lamr cafe, Ihe oily pan is 001 diffipaled or burnl,
as il is hy calcination in a naked fire, bUI has lime 10
IInite wirh fome of Ihe eanh aod ,cid of the mixt, in
fuch a manOff as
10
form a I"'e volarile alkali.
To proveo that on Ihis occafion, as \Vell as on all o·
tlters, \Vhere unpurrefied bodies yicld a volatile alkali,
this (all is the produ8 of the ore, we need only obferve,
Ihat in thefe diOillalions il never rifes lill arter fome
pan of rhe plllegm of Ihe acid, ,nd eveo of Ihe Ihick oil
uf Ihe mixt, is come over
j
which never is the cafe when
it is formed before·hand io the body which is Ihe fubjeél
of rhe operarion, as it is in thofe which have undergooe
pmrefa8ioo: For Ihis falt, beiog much lighter aod more
s
T
R y,
,'olalile Ihan Ihofe olher fubOaoces, rifes or cDude be–
fore Ihem in diaillalioo.
A General
ViC1U o/ Cbemim! Decolllpojilion.
TH ou
CH
we have eoofidered
,11
Ihe fubOances which
enler inlo Ihe eompofilion of vegetables.
anim~ls,
anu
minerals, whelher as primary or as
f~condary
principies,
it will not be improper 10 filew io whar order we oblaio
Ihefe principies from Ihe feveral mixls ; and efpecially
froOl vegelables and aoimals, becaufe Ihey are mueh
more complicmd Ihan minerals. This is called
anal¡.
jing
a compouod.
The method moOcommonly rakeo 10 drcompofe bo·
die! is hy applying to them fucccffive dcgrm of hear,
from Ilre gentkll 10 Ihe moa violent,
in
approprialed
velfels, foconlrived as to colle8 whal exhales flom the1l1.
TIy tlris means Ihe principies are gradually feparaled from
each other; Ihe mo(l volalile rife firO, and Ihe rel! fol·
10\V in order, as Ihey come lObe acfied
On
by Ihe proper
degree of hear: And this is c,lI.d
diJIil/Qcion.
RIIt
il being obferved thar fire, applied 10' lhe decom·
pofirion of bodies, moti commonly alrers Ihei r fecondary
principies very feofibly, by combining dlelll in a different
manner \Vith each other, or eveo partly decompofing
them, and reducing them 10 their primitive prinCIpies.;
olher meaos have been ufed tO feparate Ihofe principies
wilhoul the hd? of fi re.
Wirh this riew Ihe mim 10 be decompofed are forci–
bly comprell'ed, in older to fqueeze out of themall fuch
parls of Iheir fubflance as they will by Ihis means pAr(
\Vilh ; or elfe thofe mixls are for a long lime trilurald,
eilher along wilh water, whieh earries off all Iheir fa–
lioe and r.'ponaceous conlenlS; or with folvenls, fuch
as ardenl fpirirs, eapable of laking up every thing in
Ihem Ihar is of an oily or refinous oature.
We (hall here give a fuccinél accounl of Ihe e!feéls of
thefe different melhods, as applied
10
Ihe principal fub
Ilances among vegelables and aoimals, and likewife 10
fome minerals.
rJ,.
ANALYSIS ifV ECETABLE SUBSTANCrs.
A vaa many vegelable fubOanm, fuch as kernelsand
feeds, yield by Orong compreffion great quaolilies of
mild, f,t, unéluous oils, which are not folable iD ardent
fpirits: TII&
are
whal \Ve called
t1P"ffi'd oilt.
They
are alfo fome times called
¡al oilt,
00 account of Iheir
unlluoufoefs, in ",hich Ihey exceed all olher fom of
oil. As thefe oils are oblained wilhout Ihe aid of 6re,
it is cerrain thar they exiOed in Ihe mixt jull as we fce
Ihem, and Ihat they are not in the leaO allered
j
which
could not have been Ihe cafe had they been oblained by
diOillation: For Ihal never produces any oils bUI fuch as
are acrid aod
folu~le
io fpirit of wine.
Some vegelable
11latte~s,
fuch as Ihe rind of cilroos,
lemons, oranges,
&c.
alfo yieId, only by beiog fquee.
ud belween Ihe fingers, a grw deal of oil. This fpim
OUI in fine finall jels, which beingreccivcd upon any po·
li(hed furface, fuch as a looking-glafs, ruo logelher, aod
form a liquor Ihat is a real oil.
But