Vanadium is the 23rd element. It's a simple gray metal that has a remarkable property — it acts as a natural and effective spermicide. In some ways, it's a better spermicide than any of those regularly on the market.
Spermicides work by damaging the lining of sperm cells. But because the lining on those cells isn't unique, anything that damages the lining of sperm also damages the lining of all the cells in the vicinity — and those are delicate cells. It's hard to find a spermicide that isn't also an irritant.
Vanadium takes out sperm using a very particular method. Sperm cells have a mechanism in their tails that allows the tails to wiggle and the sperm to swim forward. Vanadium snaps the mechanism and the tail. It's particular enough to be exclusive to sperm, and strong enough to take out all the sperm it comes in contact with.
So why isn't it on the shelves? Vanadium doesn't just hack into the body one way; it does a lot of other stuff, too. For some reason, it lowers blood glucose dramatically. In some places, vanadium water is sold as a "cure" for diabetes. (Just to be clear, it isn't a cure for diabetes.)
And there's another problem — too much vanadium in the system results in a metallic taste in the mouth as vanadium gets deposited on the tongue. The vanadium is in a state that makes both the metal and the tongue appear bright green, wich means if you come into the office on Monday with a green tongue, either you have to convince people you spent the weekend in a vanadium mine or they'll know more about your weekend than you might care to let on.
Image: Alchemist HP.