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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