10. Mercury

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If you have ever read the safety instructions that are recommended for cleaning up a broken compact florescent light bulb, you already have some idea how dangerous mercury can be. Apparently, the magical look of this liquid metal intrigued our ancestors enough to make them think it would be a good cure for things like syphilis. It was also touted as something that you could drink as an ingredient a “health tonic” that would allow you to live forever and walk on water. The reality of it is that mercury is much more likely to just kill you than do any of those things.