White particles?

[Son Of Skyline]

Does anybody have any issues with the undissolved white particles found in IO salt when you get moisture in the bucket? I'm nearing the end of my bucket (salt is hard now) and I'm noticing more and more of this stuff when I mix new water. The stuff never dissolves. I've never really paid much attention to it but now I'm wondering if I should be adding this stuff to my tank.

Thanks in advance.