The description of the Prestige mission called "A Pinch of Salt" states that...

The best way to keep slimes at bay is with copious amounts of rock salt. Slimes just hate the stuff as touching it makes them dissolve. It's not pretty.

Research teams stationed in lichenous lairs will often surround their entire camp with rock salt so that they don't end up some slime's dinner. As you can imagine, they go through the stuff fast. When they run low, a squad is called in to battle their way to the camp and deliver the life saving seasoning.

So when a member of the slime family supposedly touches the salt, they dissolve. Yet, I have PROOF that the salt does NOT work every time. Here's my discovery no so long ago. http://imgur.com/8k5kYz9 . As you can see the Lichen of the slime family has passed the barriers of the mission description and has DEFIED the LAWS of SLIMES.