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Author: Subject: Metal hydrides

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[*] posted on 5-8-2011 at 12:41
Metal hydrides

The search didn't provide any proper threads about the metal hydrides so I made one.
Alkali metal hydrides can be made by just heating molten metal under hydrogen atmosphere. I'm not sure if that can be achieved under normal pressure or not. However that sounds at least very dangerous if not difficult. So I'm thinking about other hydrides that could be turned into alkali metal hydrides by metathesis. Magnesium for instance. Wikipedia states that it can be made by hydrogenation of magnesium anthracene under mild conditions. I wonder what "mild conditions" actually mean in this case. Wikipedia also claims that magnesium hydride has been around for thousands of years. How was it prepared before era of high pressure hydrogenators. Would the methods used back then provide a viable method for an amateur chemist to make the hydride nowadays or are the yields just too low to be practical?
Any thoughts about other hydrides?
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Thought-provoking Teacher

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[*] posted on 5-8-2011 at 12:59

Calcium hydride (CaH2) was during wartime used as a portable hydrogen source. On heating it decomposes into its constituent element. And CaH2 can also be made by direct union of the elements.

Most hydrides are above the paygrade of hobbyists, so you won't find that much here at SM...
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International Hazard

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[*] posted on 5-8-2011 at 16:19

I had the opportunity to experiment with some 'homebrew' sodium hydride (NaH) a few months ago. I don't get into organic chemistry much so I didn't get as far as using it for reactions that require a strong base. IMO, hydrides are even harder to handle and store than the alkali metals, themselves - at least for someone like me.

Hydrides don't require much arm-twisting to release hydrogen. Carefully heat some, you have a semi controllable release of hydrogen. The dry, freshly prepared powder reacts viciously when it contacts water - gives a hissing flame like an angry, rabid cat. :o Hydride that isn't so fresh only 'sparks' when contacted with water.

Interesting stuff but it's easy to see how one could get hurt or accidentally start a fire if ignorant and/or careless with it. It's one of the only chemicals I've handled which is actually underestimated in homer literature (MSDS, Wiki, etc) IMHO.

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International Hazard

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[*] posted on 5-8-2011 at 20:30

has anyone opened a fully charged NiMH battery in an attempt to remove the metal hydride?

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Hazard to Self

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[*] posted on 6-8-2011 at 14:58

I think the Hydrogen in NiH battts is interstitial Hydrogen ie not a normal type of hydride.
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