Among a bunch of old pool junk that came with my house is a plastic garbage can full of a white powder and a coffee can. I have no idea what it is, or how old it is. The previous owner used a pool service, so it may date back to the owner before that, but it seems to be intact as far as mysterious white powders go
I thought it might be chlorine, but it either didn't register or immediately bleached out on my test kit (Taylor 2006). It doesn't react with vinegar, so it's not baking soda-like. Adding it to a pH test turns it yellow, so I was thinking it might be a powdered form of acid. My pool does seem to have a continuous acid demand of ~1qt per 7-10 days, so maybe the previous owner used a powdered product to manage that. I want to dispose of it safely or use it up to get rid of it, but either way I need to identify it first. Any ideas?