[Earl]

I found this info at The Cook's Thesaurus

Kosher salt also is preferred over table salt for canning and pickling. Like pickling salt, kosher salt is free of iodine, which can react adversely with certain foods. Some brands of kosher salt contain yellow prussiate of soda, an anti-caking agent, but unlike the anti-caking additive in table salt, it doesn't cloud pickling liquids. The only drawback to using kosher salt for pickling or canning is that the grains are coarser and flakier, and can't be packed as tightly into a measuring cup as pickling salt. This raises the risk that the salt won't be properly measured. To get around this problem, measure by weight instead of volume. With its large grains, kosher salt isn't a good choice for baking.