Wilhelm PfefferDied 31 Jan 1920 at age 74 (born 9 Mar 1845).Wilhelm (Friedrich Philipp) Pfeffer was a German botanist whose work on osmotic pressure made him a pioneer in the study of plant physiology. With Julius von Sachs, he was a leader in systematizing the fundamentals of plant physiology. In 1877, while investigating cell metabolism, he devised a semi-permeable membrane for the study osmosis. By measuring osmotic pressure, a technique he developed, Pfeffer found that pressure depends on the size of the molecules that are too large to pass through the membrane. Thus, he had a method to measure the size of such giant molecules. However, he was unable to find a mathematical relationship to predict osmotic pressure, which was furthered by the work of van't Hoff. |
