204
OILS, ADULTERATION OF
o, figs. 105 and 108; the spring, or relieving wedge.
e, lighter rail; d, lifting-rope to ditto.
/, /> /, /> flooring overhead.
g, figs. 105 and 108; the hack iron, or end-plate minutely perforated.
h, the liorse-hair bags (called hairs), containing the flannel bag, charged with seed;i, the dam-block; m, the spring wedge.
Fig. 107, A, upright guides; C, and D, spring and driving stampers; E, liftingroller; F, lifting shaft; a, a, cams of stampers.
Fig. 108, a view of one set of the wedge-boxes, or presses; supposing the front ofthem to be removed.
Fig. 108; o, driving wedge; g, backiron; h, hairs; i, dam-block; k, speer-ing or oblique block, between the twostampers; l, ditto; n, ditto; m, spring,wedge.
When in the course of a few minutesthe bruised seeds are sufficiently heatedin the pans, the double door FF is with-drawn, and they are received in the bags,below the aperture G. These bags aremade of strong twilled woollen cloth,woven on purpose.. They are thenwrapped in a liair-cloth, lined withleather.
The first pressure requires only a dozen blows of the stamper, after which the pouchesare left alone for a few minutes till the oil has had time to flow out; in which intervalthe workmen prepare fresh bags. The former are then unlocked, by making the stamp erfall upon the loosening wedge or key, m.
The weight of the stampers is usually from 500 to 600 pounds; and the height fro 01which they fall upon the wedges is from 16 to 21 inches.
■ Such a mill as that now described, can produce a pressure of from 50 to 75 tonsupon each cake of the following dimensions : 8 inches in the broader base, 7 inchesin the narrower, 18 inches in the height; altogether nearly 140 square inches in surfa ce >and about f of an inch thick.
OILS, ADULTERATION OF. M. Heidenreich has found in the applicationof a few drops of sulphuric acid to a film of oil, upon a glass plate, a means of ascer-taining its purity. The glass plate should be laid upon a sheet of white paper, and adrop of the acid let fall on the middle of ten drops of the oil to be tried.
With the oil of rape-seed and turnip-seed, a greenish blue ring is gradually formed a *a certain distance from the acid, and some yellowish brown bands proceed from th ecentre.
With oil of black mustard, in double the above quantity, also a bluish green color-
With whale and cod-oil, a peculiar centrifugal motion, then a red color, increasinggradually in intensity; and after sometime, it becomes violet on the edges.
With oil of cameline, a red color, passing into bright yellow.
Olive-oil, pale yellow, into yellowish green.
Oil of poppies and sweet almonds, canary yellow, passing into an opaque yellow.
Of linseed, a brown magma, becoming black.
Of tallow or oleine, a brown color. . , g
In testing oils, a sample of the oil imagined to be present should be placed alongsiof the actual oil, and both be compared in their reactions with the acid. A good w Jof approximating to the knowledge of an oil is by heating it, when its peculiar obecomes more sensible. — ■
Specific gravity is also a good criterion. The following table is given by M- ndenreich :—