metalresearcher - 13-3-2017 at 11:21
I heard that that would produce Ca metal, while I thought that Ca is more reactive than Al.
3 CaO + 2 Al => 3Ca + Al2O3
168 54
So I mixed 3 parts (168/54), 1 gram of CaO with 1 part (0.33g) Al powder and ignited it with KClO3 + sugar.
I saw a very slow progressing reaction on the heap which took more than 10 seconds, despite the tiny amount. The reaction hotspot got orange / yellow
hot.
So probably all the Ca metal is burnt again in the air.
Did anyone try this reaction successfully ?
TheMrbunGee - 13-3-2017 at 11:27
Yes, that is what happens, reaction is slow because of high melting point of calcium, but because of high temperature, calcium burns in air and what
you mostly get is - calcium and aluminum oxides and other substances in unimportant quantities.
MrHomeScientist - 13-3-2017 at 12:05
If carried out in a reactor under inert atmosphere, it should be possible to collect the Ca formed. Then the problem would be raising it to high
enough temperature to also melt the aluminum oxide, to afford good metal separation. It sounds like the actual thermite doesn't produce much heat.
byko3y - 13-3-2017 at 12:51
This method definitely works, because it was the main commercial route. To recover the calcium you need to distill it in vacuum. Sodium is much more
easier both to make and to distill, so price of 99% sodium is 160$/kg, while the price of 98.8% calcium metal is 250$/kg. Pretty much the only viable
application for elemental calcium is making calcium hydride, which is a perfect dehydration agent that gives insoluble products.