Molten elements are all actually LAVA, so if you delete lava, all the molten elements go away. The original type is stored in .ctype, so molten PSCN would be LAVA(PSCN) and molten NSCN would be LAVA(NSCN)
If you want to refer to a specific ctype, you can't do that with basic commands. With more advanced Lua commands you could.