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RAPE OIL

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Originally appearing in Volume V22, Page 900 of the 1911 Encyclopedia Britannica.
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RAPE OIL , an important fatty oil, known also as " sweet oil," either expressed or extracted from the crushed seeds of cultivated varieties of the cruciferous genus Brassica, the See also:parent See also:form of the whole apparently being the See also:wild navew, B. campestris. Under the See also:general name " rape oil " is included the See also:pro-duce of several See also:plants having distinct and fairly See also:constant characters, and one of these See also:oils—colza (q.v.)—is a very well-known commercial variety. In See also:Germany, where the See also:production of rape oil centres, two See also:principal oil-seeds—rape and Riibsen—are well-recognized. (See RAPE.) The oil yielded by these seeds is, in See also:physical and chemical properties, practically the same, the range of fluctuations not being greater than would be found in the oil of any specific See also:seed under similar varying conditions of production; the See also:winter varieties of all the seeds are more productive than the summer varieties. Newly pressed rape oil has a dark See also:sherry See also:colour with, at first, scarcely any perceptible See also:smell; but after resting a See also:short See also:time the oil deposits an abundant mucilaginous slime, and by taking up See also:oxygen it acquires a See also:peculiar disagreeable odour and an acrid See also:taste. Refined by the See also:ordinary processes (see Olrs), the oil assumes a clear See also:golden yellow colour. In specific gravity it ranges between o•9112 and o•9117 in the raw See also:state, and from 0.9127 to 0.9136 when refined; the solidifying point is from -4° to -6° C. The principal uses of rape oil are for See also:lubrication and See also:lighting; but since the introduction of See also:mineral oils for both these purposes the importance of rape has considerably decreased. It is but little employed in See also:soap-making, as it saponifies with difficulty and yields only an indifferent product. In Germany it is very considerably used as a See also:salad oil under the name of Schmalzol, being for that purpose freed from its biting taste by being mixed with See also:starch, heated till the starch is carbonized, and filtered after the oil has cooled. The offensive taste of rape oil may also be removed by treatment with a small proportion of sweet spirit of See also:nitre (nitrous See also:ether). In the See also:East Indies rape oil and its equivalents, known under various names, are the most important of oils for native use.

They are largely consumed as See also:

food instead of ghi under the name of " metah " or sweet oil, but for all other purposes the same sub-stance is known as " kurwah " or See also:bitter oil. Most natives prefer it for the preparation of their curries and other hot dishes. Rape oil is the subject of extensive See also:adulteration, principally with the cheaper See also:hemp oil, See also:rosin oil and mineral oils. These sophistications can be most conveniently detected, first by taste and next by saponification, rosin oil and mineral oil remaining unsaponified, hemp oil giving a greenish soap, while rape oil yields a soap with a yellow tinge. With concentrated sulphuric See also:acid, fuming nitric acid, nitrous acid, and other reagents rape oil gives also characteristic colorations; but these are modified according to the degree of purity of the oil itself. The presence of See also:sulphur in rape and other cruciferous oils also affords a ready means for their See also:identification. See also:Lead See also:plaster (emplastrum lithargyri) boiled in rape oil dissolves, and, sulphide of lead being formed, the oil becomes See also:brown or See also:black. Other lead compounds give the same black coloration from the formation of sulphide.

End of Article: RAPE OIL

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