OIL AND FAT.—­A machine in most respects like a whizzer is used for the “extraction of oil and fat and oily and fatty matters from woolen yarns and fabrics, and such other fibrous material or mixtures of materials as are from their nature affected in color or quality when hydrocarbons are used for the purpose of extracting such oily or fatty matters, and are subsequently removed from the material under treatment by the slow process of admitting steam, or using other means of raising the temperature to the respective boiling points of such hydrocarbons, and so driving them off by evaporation.”  In the centrifugal method carbon-bisulphide, or some other volatile agent, is admitted and is driven through the material by centrifugal force, when the necessary reactions take place, and is allowed to escape in the form of hydrocarbons.  A machine differing only in slight particulars from the above is used for cleansing wool.

LOOSE FIBER.—­Another application is the drying of loose fiber.  Two distinctive points deserve to be noticed in the centrifugal used for this purpose.  An endless chain or belt provided with blades moves the material vertically in the basket, and discharges it over the edge.  During its upward course the material is subjected to a shower of water to wash it.

OIL FROM METAL CHIPS.—­Very material savings are made in many factories by collecting the metal chips and turnings, coated and mixed with oil, which fall from the various machines, and extracting the oil centrifugally.  The separator consists of a chip holder, having an imperforate shell flaring upward and outward from the spindle (in fixed bearings) to which it is attached.  When filled, a cover is placed upon it and keyed to the spindle.  Between the cover and holder there is a small annular opening through which oil, but not chips, can escape.  Fig. 29 (Pat. 225,949—­C.F.  Roper) is designed (like the greater part of the drawings inserted) to show relative position of parts merely, and not relative size.  This style of machine can be used for sugar separating (Pat. 345,994—­F.P.  Sherman) and many other purposes, to which, however, there are other styles more especially adapted.

[Illustration:  Fig. 29.]

FILTERERS.—­There are two distinct kinds of centrifugal filterers, working on different principles.  Petroleum separators (Pat. 217,063) are of the first kind.  They are in form in all respects like a sugar machine.  The flakes of paraffine, stearine, etc., which are to be extracted, when chilled are very brittle and would be disintegrated upon being hurled against a plain wire gauze and would escape.  Even a woven fabric presents too harsh a surface.  It is necessary to have a very elastic basket lining of wool, cotton, or other fibrous material.  The basket itself may be either wire or perforated, but must have a perfectly smooth bottom.

As the pressure of the liquor upon the filtering medium per unit of surface depends entirely upon its radial depth, mere tubes, connecting a central inlet with an annular compartment, will serve the purpose quite as well as a whole basket.  In this style of machine (Pat. 10,457) the filtering material constitutes a wall between two annular compartments.  The outer one is connected with a vacuum apparatus.