Pressure experiments are experiments performed at pressures lower or higher than atmospheric pressure, called low-pressure experiments and high-pressure experiments, respectively. Pressure experiment are necessary because substances behave differently at different pressures. For example, water boils at a lower temperature at lower pressures. The equipment used for pressure experiments depends on whether the pressure is to be increased or decreased and by how much. A vacuum pump is used to remove the air out of a vacuum vessel for low-pressure experiments. High-pressures can be created with a piston-cylinder apparatus, up to 5 GPa (50 000 bar) and ~2000 °C. The piston is shifted with hydraulics, decreasing the volume inside the confining cylinder and increasing the pressure. For higher pressures, up to 25 GPa, a multi-anvil cell is used and for even higher pressures the diamond anvil cell. The diamond anvil cell is used to create extremely high pressures, as much as a million atmospheres (101 GPa), though only over a small area. The current record is 560 GPa, but the sample size is confined to the order of tens of micrometres (10-7 m).
Famous quotes containing the words pressure and/or experiment:
“By school age, many boys experience pressure to reveal inner feelings as humiliating. They think their mothers are saying to them, “You must be hiding something shameful.” And shucking clams is a snap compared to prying secrets out of a boy who’s decided to “clam up.””
—Ron Taffel (20th century)
“Mathematics alone make us feel the limits of our intelligence. For we can always suppose in the case of an experiment that it is inexplicable because we don’t happen to have all the data. In mathematics we have all the data ... and yet we don’t understand. We always come back to the contemplation of our human wretchedness. What force is in relation to our will, the impenetrable opacity of mathematics is in relation to our intelligence.”
—Simone Weil (1909–1943)