Oleoscopicity and Organic Deliquescence of Hydrophobic Compounds Under a Hydrocarbon Atmosphere

ABSTRACT This paper examines the acquisition of organic solvent by hydrophobic organic compounds from atmospheres enriched in organic vapor. Hygroscopicity commonly refers to a substance acquiring water vapor from a humid atmosphere, and deliquescence occurs when a solid substance acquires sufficient water vapor to the point that it dissolves into a homogeneous liquid solution. As the terms hygroscopicity and humidity have become so commonly and inexorably linked to water in the scientific literature, we introduce the terms oleoscopicity and oledity to refer to circumstances where a substance acquires organic vapor from the atmosphere. Our initial investigation into trends for oleoscopicity comprised studies of three families of organic compounds under atmospheres of n ‐hexane as a model solvent. Several of the compounds studied deliquesced by forming homogeneous liquid solutions with hexane acquired from the atmosphere, and deliquescence was observed to require the hexane vapor having exceeded a critical relative oledity. We report how this form of (organic) deliquescence—with hydrophobic compounds acquiring organic solvent—parallels many aspects of standard (aqueous) deliquescence.