This apparatus has an oil-cup consisting of a cylindrical brass or gunmetal vessel, the cover of which is provided with three rectangular holes which may be closed and opened by means of a perforated slide moving in grooves; the movement of the slide causes a small oscillating colzaor rape-oil lamp to be tilted so that the flame (of specified size) is brought just below the surface of the lid.
In Germany, where the production of rape oil centres, two principal oil-seeds - rape and Riibsen - are well recognized.
Newly pressed rape oil has a dark sherry colour with, at first, scarcely any perceptible smell; but after resting a short time the oil deposits an abundant mucilaginous slime, and by taking up oxygen it acquires a peculiar disagreeable odour and an acrid taste.
The principal uses of rape oil are for lubrication and lighting; but since the introduction of mineral oils for both these purposes the importance of rape has considerably decreased.
The offensive taste of rape oil may also be removed by treatment with a small proportion of sweet spirit of nitre (nitrous ether).
