OIL
O I L
( 181 )
Oil of Ben. Oleum Balani of the ancients.
This oil is procured by expreffion from thedecorticated feeds of the Guilandia Moringa,a tree that grows in Ceylon, Ethiopia, Egypt and Arabia, ioo lbs. of the feeds yield 23 lbs.of a yellowifh limpid oil, inodorous, infipid,and which does not become rancid by expofureto the air. On this account it is much ufed bythe Italians as the balls of their perfumed oils,which are commonly prepared by filling a cover-ed difh with alternate layers of cotton foaked inBen oil, and flowers of jafmine, violet, orange,&c. after the difh has been fet in hot water, orin the funfhine for a few days, its contents areunpacked and the oil fqueezed out of the cotton,which by this Ample procefs is found to behighly impregnated with the aromatic qualitiesof the flowers.
There are feveral other kinds of expreffedoils employed in various countries as food, orin lamps, &c. but of which we (hall only par-ticularize the two following, as being fpeeimensof the vegetable butters.
Butter of Cacao.
This oil is procured from the chocolate nut,the fruit of the Theobroma Cacao . The nutsare fir 11 gently roafted till the thin outer hulkfhells off, and are then beaten up into a fmooththin pafte by the addition of eight times theirweight of warm water. This mixture beingthen kept at a gentle boiiing heat for fomehours, a liquid oil rifes to the furface, whichwhen the fire is withdrawn concretes into afebaceous matter of a grey colour, and amount-ing to about 45 per cent, of the entire nuts.This oil may be rendered nearly white by re-peated wafhing in fcalding water. It has littleor no tafte, but retains for a long time thedelicate flavour of chocolate, and appears to bethe leaft difpofed of any of the oils to becomerancid. It is employed in America as anarticle of food, and in the compofition of un-guents and medicated foaps.
Many of the palms produce a hard nut like adate Hone, but abounding in oil. Of thefe thetwo principal are the Cocos butyracea andEleieis guineenfis. The fruit when ripe is heap-ed up and fiightly fermented in order in fomemeafure to foften it; being then coarfely pound-ed it is macerated in hot water, and thus bydegrees parts with its oil, which colleCts on thefurface of the water, and by cooling concretesinto a folid cake: it is purified by wafhing inhot water and is then fit for ufe. It has a lightlemon yellow colour, little or no tafte, but a
high odour and flavour like that of the Eloren-tine iris: by long keeping it becomes rancid,and then is nearly white and almolt withoutodour. It is largely ufed by the negroes inAfrica and the Welt Indies as food, and inEurope is employed in medicine, and in thecompofition of the belt yellow foap.
Oils Vegetable, Essential, or Volatile-
Thefe oils are fo called becaufe they areevaporable at a moderate heat without decom-pofition, and becaufe in them the odour orfragrance, or as it was called by the old chemifts,the ejfence of vegetables refides. They are notconfined to any particular parts of a plant, butexilt in minute cells diftributed through theroot, the wood, the bark, the leaves, the blof-foms, and feeds. The part in which they occurlefs frequently than any other is the lobe orcotyledon of the feed, the peculiar feat of thefixed oil, while the hulk or cover of the feed isalways more or lefs impregnated with volatileoil, the acrimony of which defends in fomedegree the rudiments, of the young plant fromthe depredation of infeCts..
The method of extracting the volatile oildiffers for the molt part very materially fromthofe which we have already defcribed as prac-tifed for the fixed oils. Thofe which areprocured from the rinds of the lemon, theorange, and the bergamotte orange are theonly ones capable of being obtained by expref-fion, which is performed in the followingmanner. A fmall wheel with its circumferencefet with fliort nails is put in motion, and alemon or orange is applied to it till the wholeof the yellow outer rind is th'us rafped away:the rafpings fall to the bottom of the cafe inwhich (he wheel turns, and when a fufficientquantity is.collected, are fqueezed between twoplates of glafs; by this gentle preflure theeffential oil flows from the ruptured cells intoany convenient veflel placed to receive it, andundergoes no further preparation except that ofbeing allowed to reft till the water and otherimpurities have fubfided.
A method analogous to that by which thevegetable butters are obtained is fometimespraftifed in India for procuring that deliciousand coftly perfume the oil or attar of rofes.Tor this purpofe a clean calk or large glazedearthen jar is filled with rofe leaves carefullyfcparated from the calyxes, and fpring waterpoured on juft fufficient to cover them : theveflel with its contents is then fet in the funfor two or three days, and taken under coverduring the night. At the end of the third or