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 también era un ávido fotógrafo aficionado.
reference_flipped: Regnault también era una ávida fotógrafa aficionada.