Strong surface adsorption of aqueous sodium nitrite as an ion pair

We describe the first detailed experimental characterization of surface adsorption of an aqueous ion pair and quantify the unusual surface behavior of sodium nitrite, a ubiquitous component of natural waters. The onset of unusually strong adsorption at concentrations as low as ca. 0.1 M resembles the controversial ‘Jones–Ray Effect,’ wherein 13 salts exhibited surface tension minima in the millimolar region before resuming the normal linear increase with bulk concentrations. Given the compelling analogy recently found between adsorption of ions to the air–water interface, and the Hofmeister Effects of biochemistry, these results have important implications for the mechanism underlying these phenomena.