How Hydrotropy Explains the Influence of Dissolved Gases on the Properties of Aqueous Salt Solutions

Dissolved atmospheric gases are typically neglected in models of aqueous electrolytes, yet several past examples in the literature reveal physicochemical property anomalies (e.g., changes in electrical conductivity) upon degassing. Here, we use classical molecular dynamics simulations to investigate whether dissolved nitrogen can reorganize the microscopic structure of 0.5 M potassium salt solutions (KX). These simulations closely mimic previous experimental work by Ninham and Lo Nostro, which reported unusual conductivity changes depending on whether dissolved gas was present. By comparing systems with and without N₂ for a series of halide and molecular anions, radial distribution functions, coordination numbers, and spatial distribution functions reveal that N₂ perturbs electrolyte structure through collective, hydrotropy-like solvent organization. Molecular anions with diffuse hydration shells display anisotropic gas-anion interactions and support weak spatial correlations of N₂ molecules, whereas halides remain structurally rigid and largely insensitive to N₂. Viewed in terms of hydrotrope-like aggregation between gas and anions, these results explain the conductivity anomalies reported in earlier experiments. Altogether, the effects on the conductivity due to the dissolved gas arise not from local kinetic changes but from mesoscale solvent structuring driven by gas-ion-water cooperativity, providing a molecular-level explanation for gas-mediated ion-specific phenomena in aqueous electrolytes.