Jules Violle

Infobox Scientist
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birth_date = November 16 1841
birth_place = Langres
death_date = September 12 1923
death_place = Fixin
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nationality = French
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field = physics
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known_for = solar constant luminous intensity Fulcanelli
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Jules Louis Gabriel Violle (November 16 1841, Langres - September 12 1923, Fixin) was a French physicist and inventor.

He is notable for having determined the solar constant at Mont Blanc in 1875, and, in 1881, for proposing a standard for luminous intensity, called the Violle, equal to the light emitted by 1 cm² of platinum at its melting point. (It was notable as the first unit of light intensity that did not depend on the properties of a particular lamp, but it was made obsolete by the candela, the standard SI unit.)

Throughout his life, Violle taught at several colleges including the University of Lyon and the Conservatoire des Arts et Métiers in Paris. He was one of the founders of the Institut d'optique théorique et appliquée and the École supérieure d'optique. He improved and invented a number of devices for measuring radiation, and determined the freezing and melting points of palladium.

Violle is believed by some to be the secret identity of Fulcanelli, a contemporary French alchemist of him whose true identity is still debated.