This thread is all about satisfying my curiosity and by no means should indicate that I am looking for something else.
Those of us who have been on TFP for a while understand that there are really only three EPA approved sanitizers that are suitable for widespread use in swimming pools, these being chlorine, bromine, and baquacil. This got me to thinking about why that is and what else has been tried in the past.
Now, I am no chemist, but I know that the first two, chlorine and bromine, are both halogens and both can be used for bleaching purposes. But what about iodine and fluorine though? Both of these elements can be classed as halogens. Iodine has long been used in the medical and pharmaceutical industry due to its antimicrobial properties. Additionally, iodine has historically had a place in making non-potable water into potable water. I'm not so sure about fluorine though. Aside from what I remember about from chemistry in college, I think that the reactivity of fluorine would make it a not-so-good choice for sanitizing water.
What else has been tried in the past for water sanitation and what would preclude the use of iodine-based or even fluorine-based products in doing the job?