I've gone organic myself to a considerable degree and find the soil is in much better shape. I dumped all my Miracle Gro into the compost pile to get the nitrogen to help break down dried leaves. I wouldn't worry about the salts since they aren't common table salt (sodium chloride) but soluble compounds that are readily absorbed by plants. Yet they are called salts and that nomenclature can throw you. So go ahead and mix it into your compost, it'll only make it richer.

You can also save it and use it for new potted stuff. I freshen mine each year with compost and have used the same potting soil for about 12 years.

If what you have is in the pounds quantities and not tons you can add them to your compost pile, a bit at a time. Maybe a scoopful for every layer of material.
Salts, that you would find in fertilizers, are a general term for what is in that material and does not refer to just table salt. Anything that has "sodium" in its name is a salt.

annpat - that's amazing you've used the same potting soil for so long. Sounds like George Washington's axe. The head has been replaced twice and the handle four times. It's the original, though. (smile)

Hah!

I keep it outdoors in a huge wire bin and I toss some manure and compost in it annually when I put it back in the bin in the fall from my pots. It freezes into a three foot high, three foot across soil bin and is just starting to thaw now. When I pot up my outdoor dock plants or window boxes, I'll fill the bottom of the huge pots with unfinished compost, a dead fish or two if I can find some, and cover that with my soil (maybe first throwing in a few plastic gallon jugs for space fillers if the pot is especially large), so the potting soil is freshened considerably from season to season---very much like the axe you describe.

The only problem is I frequently get petunias (or nicotianas) growing in my zinnia (or other) pots from a single petunia that I grew in that soil years ago. Its offspring appear every year in my pots and I usually yank them out when they are tiny and repot them in their own pots. Then I get stuck with a bunch of pink petunias that I didn't like years ago---and I still don't like---but I end up growing every year.