Saxa salt

A container of Saxa salt was present in a chip shop Graham O'Brien once visited. (TV: The Universe is Calling)

Information from invalid sources
The Fourth Doctor once dropped a large sack of Saxa salt on two Fendahleen to kill them. He arrived at this solution just after one of them had called him a "Bozo" for believing that they could be defeated with rock salt. (NOTVALID: Doctor Who? 197)