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Keywords:

  • history of science;
  • optical rotation;
  • François Arago;
  • Jean-Baptiste Biot;
  • saccharimetry

Abstract

The year 2011 is the bicentennial of François Arago’s discovery of optical rotation. The immediate usurpation of the study of optical activity by Jean-Baptiste Biot led to the first well-known judgments of the arrangements of atoms in space. Scientists are less aware that Arago achieved something far greater than his contributions to optics, by signing the 1848 decree that abolished slavery throughout the French Empire. Opposing attitudes of Arago and Biot toward abolition, foreshadowed in their early rift over optical rotation, were surprisingly exposed in mid-century developments in chiroptics. As shown in a recent book by Levitt, Arago sought a reinvention of the whole colonial plantation system consistent with Republican principles, while Biot tried to place the cane sugar industry and slave-based economy on the quantitative foundation of saccharimetry. A reevaluation of the circumstances of abolition can celebrate both societal evolution and optical rotation on the 200th birthday of the latter. Episodes from Arago’s life that arguably created his predisposition toward abolition are emphasized: He was imprisoned several times as a young man and knew the loss of liberty, his brother Jacques witnessed slavery in Brazil and advocated abolition in travel books prepared with François, and finally, in writing the biography of the Marquis de Condorcet, the spirit behind the first, albeit impermanent French abolition of slavery in 1794, Arago found proof of concept for his comparable challenge. Curiously, the measurement of the optical rotation of crystals and sugar, the foci of Arago and Biot, respectively, remain among the greatest challenges in polarimetry. Current developments are reviewed with respect to chiroptical anisotropy and in vivo glucose detection driven by the pandemic of diabetes, a disease diagnosed polarimetrically by Biot that claimed the life of Arago.