BAROMETER 1639: Galileo Galilei challenge
the “emptiness resistance Water cannot be pumped under vacuum to a height greater than 10.2 m
Blaise Pascal's Barrel Experiment Rouen France C. 1640
From El Museo Popular Published Madrid 1889
https://www.bing.com/images/blob? bcid=SHMxbOJphuYAew
Evangelista Torricelli (1643)
He was a student of Galileo. He replace water with mercury, a fluid about 13 times denser than water.
Barometer: Greek word "baros" = weight the air in the atmosphere has a weight equal to the weight of a water column of 34 feet (10 meters). mercury column = 760 mm of Hg = 760 torr
We live in a "sea of air" that exerts a pressure analogous to the pressure of water on submerged objects.
Project Gutenberg of Canada ebook #403 BAROMETER Torricelli's type experiment in Pisa in 1644
the height of the mercury column is always fixed at 760 mm regardless the shape of the container.
“We live submerged at the bottom of an ocean of the element air, which by unquestioned experiments is known to have weight.”
https://catalogue.museogalileo.it/gallery/Torricellian Experiment.html
Blaise Pascal Paris 1647
Tested the hypothesis of Torricelli and confirmed (with experiments) that the atmosphere is indeed responsible for the height of the column of mercury
Unit of pressure pascal (Pa): Pa = 1 N/m2 a fluid about 13 times denser than water
https://www.britannica.com/biography/Blaise-Pascal
Barometer principle
At equal surface area, the mass of the column of water (10.3 m) is the same that of mercury metal (760 mm Hg).
The same observation was made by using alcohol instead of water.
The ratio: "weight of the atmosphere / surface" is a value equivalent to that of the liquid inside the tube.
https://scied.ucar.edu/sites/default/files/images/lon g-content-page/torricelli.jpg BAROMETER Air Pressure measurement (1648)
Florin Périer carried out atmospheric pressure measurements at different heights at Puy de Dôme (France).
The column of mercury fell and rose progressively of about three inches as the ascent and descent were made.
The Torricelli – Pascal hypothesis is verified.
https://scied.ucar.edu/sites/default/files/images/lon g-content-page/torricelli.jpg
Equivalent weight of the atmosphere roughly 1 kg/cm2
Force corresponding to the mass of 1 m2 of air at the earth surface
f = ma → f = mg f = (10340 kg) x (9.81 m/s2) = 1.013x105 N
since pressure = Pa = N/m2 pressure = 101.3 kPa
https://chem.libretexts.org/Courses/Valley_City_Stat e_University/Chem_115/Chapter_7%3A_States_of_ Matter/7.2%3A_Pressure
U-tube pressure gauge
The difference in level in the tube corresponds to the different pressure between the two openings
∆P in in mm of Hg
https://www.hydraulicspneumatics.com/ BAROMETER Robert Boyle setup (1660)
Used to find the relation between the pressure and the volume of a gas
V P= constant
https://kaiserscience.wordpress.com/tag/gas-laws/
The ideal gas law