Oil

O I L

( 179 )

ground, and ftrongly prefled in the ufual man-ner, by which mode of proceeding a largerquantity of oil is indeed obtained, and with lefstrouble, but of a rank difagreeable flavour,intolerable to any but thofe who have fromchildhood been accuftomed to it.

Recently drawn virgin oil has a bland almoftmucilaginous tafte, with a flight but agreeableflavour: if expofed to the air in an open bottleor calk, a white fibrous and probably albumi-nous matter is depofited, the fupernatant oilbecoming clear, and of a dilute yellow colour ;the oil being poured off into a frefh veflel, afecond depofition takes place, after which theoil if put in clean glafs vials, may be kept for a■confiderable time without alteration. If the oilis allowed to Hand on the white matter, itbecomes in a few weeks very rancid; and thecommon oil even when properly managed,cannot be preferved in calks longer than a yearand a half, or two years at the iartheft. Thefp. gr. of olive oil is =0.9153; it boils atabout 500° Fahr. and congeals at 36° Fahr.The readinefs with which it freezes renders itimproper for lamps, efpecially in cold countries;but by previoufly expofing the oil in an openclear glafs vial to the funlhine, it may be fo faramended in this refpefft, as to continue fluid at21 0 Fahr. f Olive oil is often fophifticated bypoppy-feed oil, and thus is rendered fomewhatdrying, a property which the genuine produceof the olive never exhibits. In thofe countrieswhere it is produced it is employed in food, asbutter is with us t the inferior forts are burntin lamps, or made into foaps, for the moll partof a finer quality than thole that are compofedof animal oils. It is ufed in medicine fometimesinternally, but generally externally, combinedwith wax, litharge, &c. into cerates andplafters.

Cornel Oil.

The only oil refembling that from the olive, inbeing contained not in the feed but in the pulpyfruit of a vegetable, is cornel oil. The berriesof this ihrub (Cornus fanguinea, Linn.) beingcollected when quite ripe, and then laid inheaps for a few days in order to mellow, are tohe reduced to a pulp, and prefled without heatm the ufual manner. By this treatment, from22 lbs. avoir, may be obtained fomewhat moret tan four wine pints of a fat fomewhat vifcid° r* k r *Sht green colour, and equally defti-V. e unpleafant flavour as the belt olive

01 ' , len heated with nitric acid it is con-V-e 1 oa lemon-yellow butter or wax. By

,f Scnnebicr, Ann. dc Chcm. xi. p. 93.

boiling with litharge it becomes drying ; whenfpread thin on water and expofed to the air fora month, it is converted into a white wax. Itdoes not freeze fo readily as olive oil, and laftsrather longer than this when ufed in a lamp. £

Almond Oil.

This is procured either from the fweet orbitter almond. The almonds are firft put intoa coarfe hempen or hair fack, and fliaken vio-lently, in order to detach, by . rubbing againfteach other and the fides of the fack, the outerbrown Ikin, which if retained is apt to give abitter tafte to the oil: they are then bruifed andmade into a pafte, and prefled in the ufual man-ner. 100 lbs. of almonds afford by the firftexpreflion, 25 lbs. of oil, and from the marcwhen impregnated with the fteam of hot water,may be procured 15 lbs. more of an inferiorkind. Almond oil when frefh, is of a lightgreenifh yellow colour, and is fomewhat turbid,but by time it becomes clear and colourlefs : itis flightly fweetifh to the tafte, and has little orno odour. Its fp. gr. is = 0.917. The de-gree at which it congeals is varioufly ftated at19 0 Fahr. and 8° Fahr.; the former probablyrelates to the frefh-drawn oil. The only differ-ence between the oil from fweet and that frombitter almonds is, that the latter may be keptthe longeft without growing rancid. Onaccount of its high price, at leaft in moft of thecountries of Europe , it is almoft entirely re-ftricted to medical ufes.

Poppy-feed Oil , or Pink Oil.

This oil is extradted by cold drawing fromthe feeds of the large white poppy (Papaverfomniferum . Linn.) which is largely cultivatedfor this purpofe in France, the Netherlands ,and various parts of Germany . It is tranfpa-rent and nearly colourlefs, and when well pre-pared has no other tafte or flavour than a flightone of nut-kernels. Its fp. gr. is — 0.9288 :it is one of the naturally drying oils, and likeall -of that clafs is frozen with difficulty ; it maybe cooled down to o° of Fahr. without congeal-ing. When employed in food it is fcarcely tobe diftinguifhed from olive oil, and indeed thislatter is very commonly adulterated with it.As to the quantity of oil yielded by a givenweight of the feeds, authors are by no meansagreed, and much no doubt depends not onlyon the mode of extrafting it, but alfo on thefeafon and country in which the feeds are pro-duced: from too lbs. of frefh feeds, fome flat*the produce of oil at 25 lbs, and others at 58 lbs.

c Margueron, in Ann. de Chcm xxxviii. p. 174.

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