Yes, if oxygen is introduced into the mix, and allowed to react with the Ca or Fe ions, they'll make oxides (Fe much more slowly, rusting takes a while, but Ca rather quickly) and we'll make water.
This is now the tricky part for me, how to add only hydrogen to the cell... A small standard electrolysis unit, attached to the cell, and bubbled with an airstone from the bottom would help, but we still need a preferably 100% efficient way of seperating the two, to prevent from making oxides. I doubt that simply adding electricity to the soup (term now coined by thrival concerning the various compounds and ions to be found in the cell), made up of Fe2+ and SO4(2-) in one part, and Ca2+ and SO4(2-) in the other. Adding one side "plain" (no sulfate) and the other with a sulfate group, would simply have the sulfate spread across both compartment until it equalized. It is possible to draw it across to the other side using electricity, but I don't know how much electricity that would take to reach across both compartments. Drawing the sulfate away, or the metal away is a very nice idea, though, I just thought of a way to introduce H2 to the sullfate without affecting the metals. I'll post it later.
The acid is used up, and when exposed to hydrogen, regenerated into acid again. No problems there, done properly.
Too much electricity would be to the point of making hydroxy, as in electrolysis. That would expose the metals to oxygen making oxides, and water when reacted. Very small amounts only to pull part the molecules is good. Sub-volt, and milliamp amounts should do if the gaps aren't too big. Easy enough.
Simply moving the sulfate to the metal without it being an acid (H2SO4) won't make hydrogen, you'll still have sulfates floating around. We can use small amounts of electricity to seperate them from the metals, which is part of my idea. Without the hydrogens attached to it, the sulfate isn't an acid, and can't split water by itself, although it is reactive, it can't break water's bonds.
Both sides can react at the same time, and I expect them to. Just slightly modified my idea to have SO4 "intakes" and acid release ports open to both sides of the cell, Ca and Fe (I'd like something that can has the same combining capacity, but doesn't precipitate). Uses a small, low-power electrolysis unit without the need to seperate the oxygen out.
Adding both of the chems in as sulfates is best, we won't make water intitially, they'll have maximum concentration, but need to be charged to start going (no problem, I think). Adding only one as a sulfate would give half concentration spread over the compartments, and a slower reaction.
If the acid is forced to one side, it'll produce the hydrogen there, and the other side will stay inactive. The acid will be used up, and recharged.
Just had a thought.... A double compartment cell with Ca in both sides. No battery ablity, but we can produce hydrogen on one side, and when that stops, shuffle over and recharge the acid to go after the other side. Constant production. Or we can have 2 ports to have all of it constantly reacting. I prefer the battery way, since we can recover what can prove to be a good portion of electricity used.
This idea is far from gone, there are a few bits to work out (isolating things, recharging acid reliably (think I have it), etc. but the basic idea is very sound and doable. It's definetly more complex that standard electrolysis, and will therefore be harder to get working ideally. Don't give up on it yet. And many thanks to those who have done, and can do tests in the near future (i'll see what I can do about getting some CaSO4 as a test material for charging). I'd love to see this sprout off and become a used, practical (it is fairly so now) and accepted method of producing hydrogen. Often imitated, never duplicated, done first by OUPower (namely, all the members involved in this).
