Gas Laws

The gas laws were a result of various attempts to establish the relationship of the volume and pressure of a gas at a constant temperature. The one that most people have heard about is Boyle’s Law. Robert Boyle was born in Ireland in 1627, the 14th child of the Earl of Cork.  Robert was a pioneer of modern chemistry and a founding member of the Royal Society.

In 1662 he published his second edition of his controversial scientific work, “New Experiments Physico-Mechanicall, Touching the Spring of Air, and its Effects”. This edition never explicitly stated Boyle’s law. The appendix contained a table of numbers that showed the inverse relationship between pressure and the volume of air. Edme Mariotte, who was a French priest independently published results of the inverse relationship between volume and pressure for a constant temperature in 1672. This is known in France as Mariotte’s law.

Boyle’s law is therefore written as:

P = pressure

V = volume

 Antoine Louis François Sergent dit Sergent-Marceau [Public domain]

The French physicist and mathematician Jacques Alexandre César Charles who was known for his work with gases and hydrogen balloon flights. 1787 his experiments demonstrated that oxygen, nitrogen, hydrogen and carbon dioxide gases all increased identically with higher temperatures when the pressure was held constant.

Charles’s law is therefore written as:

T = temperature

Joseph Louis Gay-Lussac, a French chemist made several daring ascents in hydrogen balloons of over 7,000 metres above sea level. During these ascents he recorded pressure, temperature and humidity measurements. From his own and others experiments he was able to deduce in 1808 that for an ideal gas of given mass and constant volume the pressure is directly proportional to its absolute temperature.

Gay-Lussac’s law is therefore written as:

The combined gas law uses the three laws discussed above to show the relationship between the pressure, volume and temperature for a fixed mass of gas.

The combined ideal gas law is therefore written as:

That’s the history and science bit, but how can this be used in a practical way.

There are many situations when engineers and scientists need to know the relationship between a gas volume, pressure and temperature. Visit my page on Hydro-Pneumatic Accumulators to see a practical application

Wikipedia - Gas laws

Science History Institute – Robert Boyle

Encyclopædia Britannica – Edme Mariotte

Chemistry Explained – Jacques Charles

Science History Institute – Joseph Louis Gay-Lussac