Ooh, hadn't thought of additives. I will edit my previous post so people don't take table salt as a recommendation for their dishwashers.
Fortunately I've not used table salt in my current dishwasher; no need to when I have 25kg bags of softening salt.
No, the blocks won't fit in my salt cellar!
It ceratinly isn't packaged or stored in the same high quality conditions as table salt, but it is designed for treatment of drinking water. I understand it's the same purity as table salf (purer in fact, as it doesn't have the additives you mention). Hopefully no toxins!
