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osmosis

osmosis (GB)
ósmosis (ES)
osmosi (I)

Passage of liquid through a semi-permeable partition, for example clay or parchment paper or cell walls in living organisms), which separates two liquids of different concentrations. Osmosis also plays a major role in metabolism. The Danish chemist Jacobus Hoff (1852-1911) discovered the phenomenon in 1874. This partition (also diaphragm ) is due to a corresponding pore size only for the molecules of a liquid (e.g. water ), but not for the solute (e.g. sugar molecules ) permeable. There is a diffusion (flowing apart) towards the concentrated solution. If you place a container-1 (with a semi-permeable outer wall) with a highly concentrated solution (e.g. sugar water) in a container-2 with pure water so that there is the same level of liquid in both containers, then the water molecules migrate to container-1 ,

Osmosis scheme

The water molecules are, so to speak, “sucked in” because there are fewer water molecules. The level in tank-1 increases (limit value) until the so-called osmotic pressure in tank-2 is equal to the hydrostatic pressure (pressure of a still liquid) in tank-1. With pure liquids such as water and alcohol However, the flow of the molecules can take place in one direction or the other, depending on the type of partition. Differences in molecular size have long been used for different applications. These include seawater desalination, the concentration of fruit juices and dairy products, as well as the cleaning of liquids (e.g. wastewater). The larger red particles shown in the picture cannot penetrate the pores of the membrane, but the blue ones can.

reverse osmosis

In reverse osmosis (also inverse osmosis), both liquids must also be separated from each other by a semipermeable membrane. Now the side with the highly concentrated liquid is pressurized (which must be higher than the natural osmotic pressure), on the other side there is water. Only the smaller water molecules can cross the membrane. The higher the pressure, the more water flows against the osmotic potential to the side with the lower osmotic potential, the chamber with the water. The osmosis is thus reversed, from which the name is derived.

The procedure is within the EU enriching at the grape authorized. The share of sugar increased by withdrawing water. With wine there is an application regarding alcohol reduction allowed. Other applications such as removal of unwanted substances (volatile phenols after Brettanomyces. corked ) and from residual sugar may only be possible with special permits.

The (not uncontroversial) reverse osmosis is still in the experimental stage and only used occasionally by larger wineries. In addition to osmosis, there are other ways to concentrate, namely as the oldest form of drying grapes or taking advantage of different boiling or freezing points using various techniques concentration like for example ion exchange,

Additional information

Complete lists of the numerous vinification measures or cellar techniques, as well as the various types of wine, sparkling wine and distillate regulated by wine law are under the keyword winemaking contain. There is extensive wine law information under the keyword wine law,

Left: By Johannes Schneider - Own work, CC BY-SA 4.0 , Link
Right picture: From unknown, public domain, link

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