Victor Regnault (1810 - 1878)
This careful and meticulous scientist was one of the first to measure the density of atmospheric air. A master glass blower, he crafted two nearly identical flasks, one being a test flask, the other being a counterpoise. Both flasks were filled with dry atmospheric air.
Next, an air pump was used to extract air from the test flask until the inside air pressure became 560 mmHg. Both flasks came to balance on a beam balance, once a mass of 1.24 grams was added to the test flask pan. mUse the information of the sketch to calculate the standard density of air.
Precisely what system Regnault used is made clear by what he placed on the left pan and right pan for each step of his procedure.
| STEP | LEFT PAN | balances | RIGHT PAN |
| (1) |
mair,1 + mglass |
= |
mair,1 + mglass |
| Air is extracted from the Left Flask. Mass is placed on the Left Pan. |
| (2) |
mair,2 + mglass + 1.24g |
= |
mair,1 + mglass |
| (1) - (2) |
mair,1 - mair,2 - 1.24g |
= |
0 |
The experiments resulted in the following equation which is solved for the density of atmospheric air.
A convenient number to use is: ρatm = 1.2 kg/m3.