Kosher salt does not have the iodine added, but it still may have some anit-caking compunds. Regardless, it's what I use, and have never had any trouble with it. That is, when I'm using sodium chloride, which isn't too often these days.
OK Michael, I'll bite...what are you using in place of NaCl? Reason I ask is just mixed a batch of PdCl using LiCl, so just curious what others are using.