I was just watching the movie "Time Line". One of the things that interested me the most was Greek Fire, a weapon primarily used in naval battles.
Personally I think Greek Fire was a form of Potassium Sodium, created right on the ship using a very simple reactive still/pressure cooker. The molten potassium sodium was ejected through a tube at the front of the ship.
Typically the reaction which creates potassium sodium, which reacts violently with water, is continuous, but, suppose there was no relief valve or outlet for the boiling potassium. The pressure buildup would cause an ejection of the potassium sodium until it "burped". The system would need some kind of valve at the outlet tube to allow pressure build up.
Maybe once I get my anthropology degree I will see if I can find funding to build such a system using ancient materials and technology.
I think I can cast the pressure cooker/reactive still using a lost wax investment casting process. The pressure relief valve could be something as simple as a heavy copper ball contained at the top, maybe even with some kind of spring. The valve could be a tapered investment cast bronze or brass system using copper seals with a screw at the bottom which tightened the valve against the copper seals.
I know a very cool professor who is an expert in the casting field who might be able to help.
I know it sounds like I just gave away everything, but, it would take an engineer like myself with the support of a chemical engineer and a casting expert to pull this off. It has not happened in many years and I doubt if it is going to happen any time in the near future.
And this idea is now copyrighted :-) If some jerk steals it I can establish I published it first.