Separator
Collier's New Encyclopedia (1921)
the name commonly applied to machines which separate the component parts of emulsions or suspen-ference, and are filled with some mineral sions, especially to the apparatus used in the separation of cream from milk. All these machines work by centrifugal action. The simplest form consists of a number of buckets (usually two or four) suspended around a central shaft which can be caused to revolve at high speed by means of gears turned either by hand or by machinery. As the buckets revolve, they assume a horizontal position, the heavier portion of the mixture being forced to the bottom. Modern machines consist of a bowl or drum, frequently containing a number of conical plates. They are continuous in action. For instance, in the De Laval separator, commonly used in dairies for separating cream, a steady stream of milk is introduced into the machine, while a stream of skim milk flows from one point and a smaller stream of cream from another. These efficient and, when machines are highly properly used, leave less than one-tenth of a per cent of fat in the milk. Another type of centrifugal separator is . This largely used in the sugar industry r industry type consists of a cylindrical basket which can be made to revolve at high speed. The sides of the basket are of fine wire screens or of cloth. Wet sugar is introduced into the basket and is flung, by centrifugal action, against the sides The water is forced through the fine mesh, while the dry sugar is retained.
What Has Changed in the Last Century
The principle Collier's described in 1921 is still the one in use: milk is spun in a bowl of stacked conical discs, and the De Laval name survives in Alfa Laval, whose separators remain standard dairy equipment, as centrifugals do in sugar refining. What has gone is the small hand-cranked farm machine with its swinging buckets; milk is now collected in bulk and separated at the creamery in self-cleaning machines handling tens of thousands of litres an hour, leaving well under the "one-tenth of a per cent of fat" Collier's called efficient. The larger change came just after this entry was written, when Theodor Svedberg built the first ultracentrifuge in 1924 and pushed centrifugal separation down to the scale of proteins and, later, cell components and nucleic acids. Spinning to separate by density is also now routine in medicine, where centrifuges divide blood into plasma, platelets and red cells.
Written for this edition, 2026.