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H E

But it mllf1 he cmfully noted, that this ¡¡,n of oil,

IhOllgh outained by expreffion only, is neverthelcfs very

diffcrent frllm the oils menriont·d before lO which the ti–

tic of

c.p"ffid

oi/¡

peculiarly bclongs: Fur"lhis is far

lighrer aud thinncr ; ·moreover, ir retains Ihe peritA o·

d OIlf

of the fruit which yidds il, .nd is (olublc in (pirit

of wine; in a word,

is a true eOenlial oil, but abounds

fo in the fruits which produce il, and is looged therein

io fuch a manner, occupying a vafl numuer of little ceJls

prol'ided in the peel for its reception, tha! a vtry flight

preffure difcharges it; which is not the cafe wilh many

vegetables that contaio al1 elfential oil.

Succulent and greeo plaols yield hycompre/liona great

deal of

li~uor

or juice, whieh conliOs of molt of the

phlegm of the falts, and a (maJl ponion of lhe oil aod

elnh of the plant. Thefe juices, beiog fet io a cool

phee for fome lime, depofit falioe cryflals, \\hich are a

cembioation of lhe ácid of the plant wirh pan of its oil

aod emh, wherein the acid is always predominaot.

Thefe falts, as is evicleot from the de!eription here gi–

Yen, bear a great refemblance tO the tartar of wioe treat–

ed of abore. They are called

effinlial ¡_I:J;

fo that

tmar might likewife be called the

effiMial foil of'Wine ,

Dried plants, and fueh as are of a ligneous, or acid

nature,

re~uire

to be long triturated with water, before

they \ViII yldd their effenrial falts. Trituratioo with wa–

ter is

excellent way to get out of them alJ their faline

and faponaceous contenrs.

A vegetable matter th at is very oily yie/ds its elfential

falr with mcch difficulty, if at all; becaufe the excef·

five

~uantity

of oil entaogles the falr fo that it canoot

<!xtriwe itfelf or !hoot into cryílals. Mr

G~rike,

io hi,

Princpl"

ofChemijl,),

fays, That if pan of the oil of a

plant be ext raé!ed by fpirit of wine, its effeotial falt

m~y

be afterwards obtaincd with Olore eafe aod in gre.ter

qu.ntity.

Effential falts are among thofe Ii,bflaoces which can–

OOt be extraé!ed from mixts by diflillatioo

for the lirll

impre/lioo of

re decompofes them.

Though the acid which predominates io Ihe elfential

(¡lIS of plant' be mofl com.monly aoalogous

lhe vege–

t:b!e acip, properly fo called. that is, to the acid of

vinegar and tartar, which i, proilably no other thao

the vitriolic acid difguired; yet it fometimes differs there–

from, and fomewh at refembles the oitrous or the marine

acid. This depends on the plates where the plant' gro",

\Vhich produce thefe falts.: If they be fubmarine plants,

their acid is a·kio tO the acid of fea·falt; if, on the coo–

trary, they grolV upoo walls, or io nitrous grounds, their

.cid is like that of nitre. Sometimes one aod the fame

planr contJins {ahs analogolls to a1l the three mioeral a–

cids; which !hews tha( the vegetaulc acid, are

other

th~n

the mioeral acids varioufiy changed by circulating

throllgh planls.

Li~uors

cootaioiog the elfential falts of plant' beiog e·

\'apormd by a gcotle heat to the coor,flcoce of hooey, or

eI'en funher, are called

,,'ra(IJ.

Hence it' is pbio,

that an extraA is nOlhing but the effeoti.1 fah of a plant,

combined with fome partide, of its oil aod earth, that re-

VOL .

11. No. 34.

101

maíned fufpended io the liquor, and are oow incorpora–

teJ by evaporalion.

Extraé!s of plants are alfo prepared by bniliog them

long io water, and then cva poratiog fome part ofil. Bu,

thefe extraéIs are of infel ior virtue; becaufe the 6re dif·

{ipates maoy of

th~

oily aod faline pam.

EMUL810NS.

Subflances which abound much in oil, Ileing bruifed

and triturated with water for fome time, ufford a liquor

of ao

opa~ue

dead-white colour like OHlk.

This liquor

coofiíls of fuch juices as the water is capable of difful–

viog, IOgether \Vith a portioo of the oil, which being oa–

tllrally indiOoluble io water, is ooly divided aod difper–

fed io the liquor, the limpidity whereof is by tha! means

deílroyed. This fon of oily liquor, in which the oil is

ooly <iivided, not dilfolved, is c.!'cd UO

",w!jiOtl.

The

oily particles io emulfions fpootaoeouOyfeparate from the

water, wheo lert at re!!, aod, uniting into geater malfes,

rife, on accouot of their lightoefs,

the furface of the

liquor, which by that meaos recovers a degree of traof–

pareocy.

vegetables, aboundiog io elfenti.i oils aod refios, be

digefled io fpirit of IVioe, the menflruum takes up tbele

oily matters, as beiog capable of diffolviog them

aoa

they may afterwards be ea{ily feparatcd hOIll it by the

atrufioo of water. The water, with which fpirit of wine

has a grMer allinity thao with oily m. ttm, feparates

them by this meaos from their fulvent,

agr~eable

th~

common laws of allioitics.

Without the help of 6re fcarre any thiog, ber,des the

fubílances already mentiooed, can be obtaioa! from a

plant: Illlt by the meao, of ditliJl;ition we are enabled tn

aoalyfe tllem more completely. lo pcofecutiog this m(–

thod of extraéling frolli a plant the feveral principies of

which it confiíls, the following order is

be obferved.

A plant being expofed

a very gentle heat, in a di–

tlilltng _elre! ret in the

hall/ellln mari<t,

yield.. a water

which retains the perfeé! fmcll thereor. Some chcrniOs,

and particlllarly the ill"lIrious Iloerhaave,

h.ve

calleu

this liquor the

fpirilllJ rd lor.

The nature of this odo–

~iferous

pan of plants is oot yet thoroughly koown; be–

caufe it is fo very volatile, that it is dillicult to fubjeé! it

to the experiments oeceO'ry for difcovering all it, pro·

perties.

ioflead of diílilling the plant io the

bolnwm

mari",

it be dillilled over a naka! fire, with the precaurion

puning a cerraio quanrity of water inro the dillilliog vef–

Id aloog with it, to preveot its fulfering a greater heat

than that of boiling water, all the effential oil contalned

in that plaot will rife together with that water, alld with

the fame degree of heal.

On tliis occafion it mufl

obfcfved, that

elfeotial

cil can be obtained ,rrom a plant lfter the

!pif/I.J

rcrior

hath been dtalVn off; ",hich gires gro\\nd

thiok thal

the voLltility of lhefe oils is owiog to thJt ¡piri!.

:he heat of boiling water is al lo fulflcient

feparate

from vegetable m.tters the fat oils whidl they cODlain :

Tbat, hOlVever, is to be done by the way of dccoAioll

onl~