Cooking salt, rather than table salt?
The anti-caking agents in table salt are simply there to help the salt flow out of a salt shaker in humid conditions. The amount of potassium ferrocyanide (one of the common additives) in a half teaspoon of table salt is negligible. But in pickling and brining a lot more salt is used and the additives could affect the outcome of the recipe. Canning salt often clumps in the box but is easily broken up and made flowable.