Historical clue formulations

• A halogen-containing salt — 2020-12-20
• Certain salt — 2015-05-10
• Disinfect, in a way, as a wound — 2015-04-24
• Halogen salt — 2006-03-05
• Halogen salt — 2003-02-09
• Salt of element #53 — 1998-06-14