Humble realized that S.E.O. is too weak and that it does not work by releasing oxygen but rather that it must be acidified to release chlorine dioxide as the active ingredient. This is also how it has been used as a hospital disinfectant. The problem was to find a safe dose and procedure that allowed this most effective antimicrobial to be used for people. Humble ended up using a nominally 28% solution which, because of a nearly 20% sodium chloride content, actually contains only 22.4% sodium chlorite.