1911 Encyclopædia Britannica/Siphon

SIPHON, or Syphon (Lat. sipho; Gr. σίφων, a tube), an instrument, usually in the form of a bent tube, for conveying liquid over the edge of a vessel and delivering it at a lower level. The action depends upon the difference of the pressure on the liquid at the extremities of the tube, the flow being towards the lower level and ceasing when the levels coincide. The instrument affords a ready method of transferring liquids. The tube is made of glass, indiarubber, copper or lead, according to the liquid which is to be transferred. The simple siphon is used by filling it with the liquid to be decanted, closing the longer limb with the finger and plunging the shorter into the liquid; and it must be filled for each time of using. Innumerable forms have been devised adapted for all purposes, and provided with arrangements for filling the tube, or for keeping it full and starting it into action automatically when required. Pipes conveying the water of an aqueduct across a valley and following the contour of the sides are sometimes called siphons, though they do not depend on the principle of the above instrument. In the siphon used as a container for aerated waters a tube passes through the neck of the vessel, one end terminating in a curved spout while the other reaches to the bottom of the interior. On this tube is a spring valve which is opened by pressing a lever. The vessel is filled through the spout, and the water is driven out by the pressure of the gas it contains, when the valve is opened. The “Regency portable fountain,” patented in 1825 by Charles Plinth, was the prototype of the modern siphon, from which it differed in having a stopcock in place of a spring valve. The “siphon champenois” of Deleuze and Dutillet (1829) was a hollow corkscrew, with valve, which was passed through the cork into a bottle of effervescent liquid, and the “vase siphoïde” of Antoine Perpigna (Savaresse père), patented in 1837, was essentially the modern siphon, its head being fitted with a valve which was closed by a spring.