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Stabilized oxychloro complex (SOC) preservative. Trade names Purite and OcuPure. This is a mixture of sodium chlorite (99.5%), sodium chlorate (0.5%), and chlorine dioxide (trace). The actual germ killing chemical is chlorine dioxide, which is generated from the other two ingredients when they are dissolved in liquid. Searching 'stabilized oxychloro complex' or 'oxychloro complex' returns almost exclusively URLs related to eye drops. It has been used as an eye drop preservative since the mid-1990s. SOC was first manufactured by Bio-Cide International, which is still in business. Bio-Cide calls it Purogene and sells it for water purification, especially for potable water storage tanks (think of an eye drop bottle as a tiny, expensive water storage tank). SOC is active over a very wide pH range including the neutral pH range preferred for eye drops. Conversely sodium chlorite by itself needs some type of acid (hydrochloric acid, acetic acid, citric acid, lactic acid) to create chlorine dioxide. Even though sodium chlorite makes up 99.5% of SOC, an eye drop that contains only sodium chlorite is probably not effectively preserved. EzriCare eye drops used only sodium chlorite as the preservative.