Charles' Law
Properties of Matter

Whose law is it anyway?

Stories from Physics for 11-14 14-16 IOP RESOURCES

The attribution of the law relating gas pressure and volume to Boyle is contested and there are at least six other scientists who may be credited with its discovery: William Brouncker, Robert Hooke, Edme Mariotte, Henry Power, Richard Towneley and Isaac Newton. On the continent, the law has been referred to as Mariotte’s law, though Mariotte’s version was developed 14 years after Boyle’s and, it is argued, built upon Boyle’s work. The historian of science, I. B. Cohen has wryly suggested the law might be renamed as ‘the law of Power and Towneley, and of Hooke and Boyle, and – to a lesser degree – of Mariotte’.

It is argued that Charles’s Law should be more appropriately attributed to Joseph Gay-Lussac. In 1802, both Gay-Lussac and John Dalton published results on the thermal expansion of gases. Dalton’s apparatus was simple — a glass tube sealed at one end with a bead of mercury to indicate expansion. From this, Dalton incorrectly concluded that there was an exponential relationship between temperature and volume. Dalton’s method is considered inferior to Gay-Lussac’s approach, which used an inverted flask in a water bath. Gay-Lussac correctly proposed a direct proportionality between volume and temperature. Though Charles carried out experiments on the relationship between the volume and temperature of gases before Gay-Lussac, Charles did not publish his results, perhaps because he had not taken care to dry his gases and his results were inconsistent. However, Gay-Lussac’s acknowledgement of Charles’s unpublished work led to the relationship becoming known as Charles’s Law.


Charles' Law
is expressed by the relation (V_1)/(T_1)=(V_2)/(T_2)
can be used to derive Ideal Gas Law
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