Help identifying powders for pool

We have two containers of white powder that the previous home owner left in the pool's pump house. I'm leaning towards tossing them out but the frugal part of me is hesitating. My pool water is lookng great (new fill and help from this form's fine contributors) so I don't want to risk anything.
I'm pretty sure the buckets (one has no labeling and the other is a leftover chlorine bucket) have DE in them but not nearly sure enough to use them yet.
So what do y'all think? Just go ahead and toss them or are there dependable means to identify them? The powder looks and feels like DE - very fine, packs tight in hand, has a few small specks of black/gray. But could it be soda ash or something else?
See pics.

I would not use them unless I was 100% certain of what they are. Powders could be DE, Baking Soda, Soda Ash, Borax, etc. Wet they could burn your hand.

1. Does it dissolve?

2. How much does 1 cup weigh?

3. Assuming it dissolves, what is the pH of 1/4 tsp added to 1 cup of water?

4. Are you SURE it was a pool chemical?

5. Buy a box of borax, baking soda, and soda ash . . . and compare.


Be careful about throwing it away, till you know more.