Page "Equation of state" Paragraph 3

Boyle's Law was perhaps the first expression of an equation of state.

In 1662, the noted Irish physicist and chemist Robert Boyle performed a series of experiments employing a J-shaped glass tube, which was sealed on one end.

Mercury was added to the tube, trapping a fixed quantity of air in the short, sealed end of the tube.

Then the volume of gas was carefully measured as additional mercury was added to the tube.

The pressure of the gas could be determined by the difference between the mercury level in the short end of the tube and that in the long, open end.

Through these experiments, Boyle noted that the gas volume varied inversely with the pressure.

In mathematical form, this can be stated as: