Reversibly switchable surfactants and methods of use thereof

A composition comprising:

• (a) water or an aqueous solution;
• (b) a switchable surfactant compound that comprises a hydrophobic portion and a nitrogen-containing salt portion that reversibly converts to a non-salt form upon contact with a source of heat and/or a flushing gas, wherein said flushing gas contains substantially no gas that liberates hydrogen ions in the presence of water;
• (c) a water immiscible liquid that is in a stable emulsion with said water or aqueous solution and forms an unstable emulsion or other two-phase mixture with said water or aqueous solution when the switchable surfactant compound is converted to the non-salt form, or
• a water insoluble solid that is in a stable suspension with said water or aqueous solution and forms an unstable suspension or other two-phase mixture with said water or aqueous solution when the switchable surfactant compound is converted to the non-salt form;
• and
• (d) a dissolved gas that liberates hydrogen ions in the presence of water,
• wherein the gas does not include HCN or HCl, and
• wherein the nitrogen-containing portion comprises a protonated amidine moiety or a protonated guanidine moiety.