Are you an EPFL student looking for a semester project?
Work with us on data science and visualisation projects, and deploy your project as an app on top of Graph Search.
Concept
Millimetre of mercury
Summary
A millimetre of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high, and currently defined as exactly 133.322387415 pascals or exactly 133.322 pascals. It is denoted mmHg or mm Hg.
Although not an SI unit, the millimetre of mercury is still routinely used in medicine, aviation, and many other scientific fields.
One millimetre of mercury is approximately 1 Torr, which is 1/760 of standard atmospheric pressure (101325/760 ≈ 133.322368pascals). Although the two units are not equal, the relative difference (less than 0.000 015%) is negligible for most practical uses.
For much of human history, the pressure of gases like air was ignored, denied, or taken for granted, but as early as the 6th century BC, Greek philosopher Anaximenes of Miletus claimed that all things are made of air that is simply changed by varying levels of pressure. He could observe water evaporating, changing to a gas, and felt that this applied even to solid matter. More condensed air made colder, heavier objects, and expanded air made lighter, hotter objects. This was akin to how gases become less dense when warmer and more dense when cooler.
In the 17th century, Evangelista Torricelli conducted experiments with mercury that allowed him to measure the presence of air. He would dip a glass tube, closed at one end, into a bowl of mercury and raise the closed end up out of it, keeping the open end submerged. The weight of the mercury would pull it down, leaving a partial vacuum at the far end. This validated his belief that air/gas has mass, creating pressure on things around it. Previously, the more popular conclusion, even for Galileo, was that air was weightless and it is vacuum that provided force, as in a siphon. The discovery helped bring Torricelli to the conclusion:
We live submerged at the bottom of an ocean of the element air, which by unquestioned experiments is known to have weight.
This test, known as Torricelli's experiment, was essentially the first documented pressure gauge.
Official source
About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.
Ontological neighbourhood
Related courses (4)
BIO-377: Physiology by systems
Le but est de connaitre et comprendre le fonctionnement des systèmes cardiovasculaire, urinaire, respiratoire, digestif, ainsi que du métabolisme de base et sa régulation afin de déveloper une réflect
BIO-378: Physiology lab I
Le TP de physiologie introduit les approches expérimentales du domaine biomédical, avec les montages de mesure, les capteurs, le conditionnement des signaux, l'acquisition et traitement de données.
Le
BIO-379: Physiology lab II
Le TP de physiologie introduit les approches expérimentales du domaine biomédical, avec les montages de mesure, les capteurs, le conditionnement des signaux, l'acquisition et traitement de données.
Le
Related lectures (32)
Hydraulic Head Determination in Unsaturated Soil
Explains hydraulic head determination in unsaturated soil and the relationship between suction and water content.
Respiratory System Anatomy and Physiology
Covers the anatomy and physiology of the respiratory system, including gas exchange and blood transport of oxygen and carbon dioxide.
Respiratory System Function: Gas Exchange and Hemoglobin
Explores gas exchange dynamics, hemoglobin affinity, and gas diffusion in the respiratory system.
Related publications (15)
Related people (5)