context: In the course of this work, he discovered that not all gases expand equally when heated and that Boyle's Law is only an approximation, especially at temperatures near a substance's boiling point.
source: Regnault was also an avid amateur photographer.
reference_original: Regnault também era um ávido fotógrafo amador.
reference_flipped: Regnault também era uma ávida fotógrafa amadora.