OSMOSIS Osmosis, or diffusion through a septum, is a phenomenon which has been known for some time.

The discovery of it is attributed to the Abbe Nollet, who is supposed to have observed it in 1748, during some "researches on liquids in ebullition." A classic experiment by Dutrochet, effected about 1830, makes this phenomenon clear.

Into pure water is plunged the lower part of a vertical tube containing pure alcohol, open at the top and closed at the bottom by a membrane, such as a pig's bladder, without any visible perforation.

In a very short time it will be found, by means of an areometer for instance, that the water outside contains alcohol, while the alcohol of the tube, pure at first, is now diluted.

Two currents have therefore passed through the membrane, one of water from the outside to the inside, and one of alcohol in the converse direction.