This zinc oxide was produced by calcining hydroxide, produced the same way I make anything else: electrolysis in NaCl. Now this is a pretty bad route, because as the zinc takes up the hydroxyl, it releases a pretty good amount of energy. Enough that it should be able to do this itself, but nonetheless I am still applying enough voltage that hydrogen is generated only at the cathode. So, the cell gets pretty hot, and I get angry at having to waste so much energy to do this!
Since zinc has a low boiling point, it can also be burned directly, but so far my attempts at this have just been blowing smoke. The ZnO doesn't settle out of the remaining nitrogen very well. I have tried to oxidize the surface of a melt by stirring (as with my attempts at lead), but since iron is soluble in zinc, my tin can crucibles keep burning through...
If anyone has suggestions for a good way to make a bulk zinc cell, I'm all ears. (Or bulk isn't necessary, I'll happily cast it into flat plates.) I've been wanting to make a zinc battery and an aluminum battery so I can produce the oxides without outright wasting the potential energy of these metals, I'm thinking run a sodium chlorate cell with a few cells in series.
I don't have any zinc chloride on hand at the moment to take a picture of, but I had some before, made by 2HCl + Zn = H2 + ZnCl2. I used most of it to tin some steel for babbit bearings - it's a pretty good flux, with a low melting point and reasonable stability (low vapor pressure). Kind of like using borax, but without the expanding foam tendancy and having a lower melting point. Colorless solid and liquid, quite deliquescent (I left it out for weeks in open air without crystallization, not that I mind, the solution can be brushed on joints easily).
Zinc sulfate (white vitriol), here made by dissolving potmetal (mostly zinc, with a few percent aluminum and smaller amounts of copper and magnesium) in sulfuric acid. I had much trouble getting this to crystallize as anything remotely useful; the liquid is viscous, apparently (milky; possibly a colloid slowing it down, from what I don't know), so any attempt to crystallize say by cooling just thickened (or froze!) the suspension, small (acicular, I hate acicular!!) crystals forming throughout it. Eventually I was able to evaporate a little, decant the solution, seperate the mat sitting on the bottom and continue evaporating. This worked until the solution started turning slightly blue (copper?) and larger diameter, colorless prismatic crystals started to appear (though at this time, most of the ZnSO4 had been removed; all of what's in the picture above). I'm guessing this new crystal is aluminum sulfate. (I don't have any crystals large enough to photograph.)