About Charles Cagniard de la Tour
Baron Charles Cagniard de la Tour (31 March 1777 – 5 July 1859) was a French engineer and physicist. == Life == Charles Cagniard was born in Paris, and after attending the École Polytechnique became one of the ingénieurs géographiques. He examined the mechanism of voice-production, invented a blowing machine and contributed to quantitative acoustics by inventing an improved siren. He also studied yeast. In 1822, he discovered the critical point of a substance in his gun barrel experiments. He sealed a flint ball in a sealed gun barrel filled with fluids at various temperatures, and rotated it to hear the splashing sound as it hit the liquid surface. He observed that above a certain temperature, there is no splashing sound. Above this temperature, the densities of the liquid and gas phases become equal and the distinction between them disappears, resulting in a single supercritical fluid phase. After this discovery, he performed quantitative measurements of the critical point of several substances such as water, alcohol, ether and carbon bisulphide. He was made a baron in 1818, and died in Paris.
Biography source: Wikipedia. The profile adds birthday-specific historical context from the Celebs Birthday Today editorial database.