Van't Hoff 1901 Nobel Lecture
| van't Hoff JH (1901) Osmotic pressure and chemical equilibrium. Nobel Lecture December 13, 1901. |
van't Hoff JH (1901) Nobel Lecture
Abstract: What is osmotic pressure? When a solution, e.g. of sugar in water, is separated from the pure solvent − in this case water − by a membrane which allows water but not sugar to pass through it, then water forces its way through the membrane into the solution. This process naturally results in greater pressure on that side of the membrane to which the water is penetrating, i.e. to the solution side.
This pressure is osmotic pressure.
It is thanks to this osmotic pressure that the sap of the oak-tree rises to the topmost twigs. This pressure was known to exist as long ago as the beginning of the 19th century, but it is only somewhat more than 20 years ago since this phenomenon has been the subject of precise measurements. It was the botanist Pfeffer who first measured this pressure in 1877 by making a membrane which satisfied the following three conditions: It was permeable to water, impermeable to sugar, and it withstood the by no means negligible pressure to which it was subjected.
Osmotic forces are in fact unexpectedly great: with a 1% sugar solution they are equal to no less than 2/3 atm.
• Bioblast editor: Gnaiger E
Labels:
Made history
