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Charles Cagniard de la Tour

French physicist (1777–1859)

Born in Paris, France, Cagniard de la Tour was educated at the Ecole Polytechnique and then spent his time as an amateur inventor. In 1819 he invented the disk siren, in which the sound is produced by air blowing through holes in a rotating disk, the pitch being determined by the speed of rotation. He made his most famous discovery in 1822; when he heated certain liquids in sealed tubes he observed that at a particular temperature and pressure the meniscus dividing liquid from vapor disappeared. Under these conditions – known as the critical state – the densities of liquid and vapor become the same and the two are identical.

In the field of biology Cagniard de la Tour discovered, independently of Theodor Schwann, the role of yeast in alcoholic fermentation. He also studied the physics of the human larynx and the sounds produced by it and invented a machine for studying bird flight.

 
 
Wikipedia: Charles Cagniard de la Tour

Charles Cagniard de la Tour (March 31, 1777 - July 5, 1859) was a French engineer and physicist.

Charles Cagniard was born in Paris, and after attending the École Polytechnique became one of the ingénieurs géographiques. He was made a baron in 1818, and died in Paris on the 5th of July 1859.

He was the author of numerous inventions, including the cagniardelle, a blowing machine, which consists essentially of an Archimedean screw set obliquely in a tank of water in such a way that its lower end is completely and its upper end partially immersed, and operated by being rotated in the opposite direction to that required for raising water.

In acoustics he invented, about 1819, the improved siren which is known by his name, using it for ascertaining the number of vibrations corresponding to a sound of any particular pitch, and he also made experiments on the mechanism of voice-production.

In 1822, discovered the critical point of a substance in his famous cannon barrel experiments. Listening to discontinuities in the sound of a rolling flint ball in a sealed cannon filled with fluids at various temperatures, he observed the critical temperature. 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.

In course of an investigation in 1822-1823 on the effects of heat and pressure on certain liquids he found that for each there was a certain temperature above which it refused to remain liquid but passed into the gaseous state, no matter what the amount of pressure to which it was subjected, and in the case of water he determined this critical temperature, with a remarkable approach to accuracy, to be 362°C. He also studied the nature of yeast and the influence of extreme cold upon its life.


This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.


 
 

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