I'm going to lean back, relax, and let you teach us all chemistry. Have fun.
In the meantime consider whether you are doing a real service to quality photo processing or are merely putting a means into peoples hands to play around with by your use of pool and laundry chemicals and the use of volumetric measure of solids.
Remember, if some newcomer to photography follows any of your advice and gets a bad result, you may discourage him from continuing. This is the responsibility that I feel with every post I make.
There are two levels here, fun photography to see what can work, and serious photography in which we want a good, repeatable process.
I can tell you what must not be in Borax except in very tiny trace amounts.
Insoluable materials (dirt, sand and etc...)
Those are at the top of my list and should be absent from good Borax. And, high quality stuff is always available in small quantities. I can get 100 - 1000 grams of analytical or reagent grade Borax any time I wish. It is available on-line.