Onesiton - 12-8-2017 at 08:55
Since I am unable to isolate magnesium in my house and ways of purchase it that I have access to are bad (sacrificial anodes that I found in the
ironmongery are of alloy and not pure), I have to find a way for isolate boron with a tolerable purity.
Currently, I am able to isolate sodium for this function (by electrolysis of caustic soda) and I have access to others materials like coal and
aluminium...
I am not sure about what is the better way to isolate boron from boron oxide, without magnesium or others unusual materials.
[Edited on 12-8-2017 by Onesiton]
violet sin - 12-8-2017 at 12:18
searched Google for "sacraficial anode, water heater, alloy composition" to see how contaminated it is..
http://www.galvotec.com/water-heater-anodes.htm
Seems like that would probably be just fine for magnesiothermic reduction of boric acid, after its roasted to the oxide. The main admixture metal is
aluminum 3.5%, and in worst case (lower cost rods) total ~5% between all contaminants.
Give it a try if you feel you can safely proceed. Start small of course. I tried twice and never got a good outcome. But at least nothing flashed
off in my face either.
CRUSTY - 12-8-2017 at 12:26
Aside from a magnesium reduction, there isn't a huge range of things you can do.
If you're willing to work with halogens, (ie do a halogenation of B2O3), you'll have a slightly wider set of options. US Patent
US 20130045152 A1 concerns the reduction of boron trihalides using alkali metals and metal borides. The metal borides require fairly high temperatures
to produce, around 800 °C for AlB2, I don't know how constrained you are when it comes to furnaces and the like.
I think it's possible to reduce boron trichloride directly using hydrogen or using a carbothermal approach, but the literature is a bit vague on
those, especially the former.
I bet you wish you had some magnesium right now, huh? 
[Edited on 12-8-2017 by CRUSTY]