Salt preservation with water softener?

So I’m trying to find the cheapest source for plain salt for preserving food and I came across Morton water softener. It says it only contains sodium chloride, comes in a 40lb bag for $9 bucks. There were others that contained other ingredients but this one was just salt. Thoughts?

It doesn't look food grade so I would be cautious.

Food grade has specific standards like not letting rats play in it and making sure there aren't metal filings or other contamination in it (note, the recent massive wave of food recalls in Canada is from this)

But then again, it might be fine.  At that price, maybe get a bag and run some experiments to make sure it's safe?