The Chemistry of Greek Fire?

[Magister Militum Flavius Aetius]

FIRST: I am in NO WAY planning to make a pyrophoric (air-igniting) material at all. This is purely a scholarly question.

So I've been doing some thinking about the whole problem of "Greek Fire." For those that don't know, "Greek Fire," actually called "Liquid Fire" or "Roman fire", was invented by a certain Kallinikos around 650-670 AD for the Roman ("Byzantine") Empire, which famously used it in their navy for centuries before the invention of gunpowder.

The recipe for it doesn't survive, but the recipe for an earlier version does:

"Automatic fire also by the following formula. This is the recipe: take equal amounts of sulphur, rock salt (NaCl with some CaCO3), ashes (charcoal, containing CaCO3, CaO, and K2CO3), thunder stone (limestone, CaCO3 and some CaO), and pyrite (FeS2, mainly) and pound fine in a black mortar at midday sun. Also in equal amounts of each ingredient mix together black mulberry resin and Zakynthian asphault, the latter in a liquid form and free-flowing (naptha), resulting in a product that is sooty colored. Then add to the asphalt the tiniest amount of quicklime (the aforementioned mixture of sulphur, rock salt, ashes, thunder stone, and pyrite). But because the sun is at its zenith, one must pound it carefully and protect the face, for it will ignite suddenly. When it catches fire, one should seal it in some sort of copper receptacle; in this way you will have it available in a box, without exposing it to the sun."

(My additional comments are in bold).

So basically what you have is Sodium Chloride, Calcium Carbonate, Calcium Oxide, Potassium Carbonate, Sulfur, and Iron DiSulfide all acting as accelerant to burn off a mix of Naptha and Pine Tar.

The problem with attempts at modern reconstructions of Greek fire typically only include the Calcium Oxide, using pure modern quicklime. What I'm trying to point out is that ancient quicklime had more compounds in it than purely Calcium Oxide.

What I can't figure out is how this would react. It looks like you're going to be burning Calcium Carbonate down to Calcium Oxide to create more accelerant. But I'm not sure how the other compounds would affect that reaction.

So my questions:

1. I'm curious as to how the other compounds would affect that process, but as I haven't gotten as far as inorganic yet, my chemistry knowledge isn't advanced enough to figure it out. I figure that the Pyrite is going to leech Sulfuric Acid, the Sodium Chloride and Potassium Carbonate will burn and intensify the fire (particularly with water present).
2. What would happen if you added Calcium Phosphate to the mixture (made from boiling bones in urine)? Calcium phosphate reacts with water (like Greek fire) to create Phosphine, which is pyrophoric and would intensify the fire (like the historical accounts). Calcium Phosphate has been suggested to have been the active ingredient in Greek Fire.

[Iskar]

I'm not really firm on chemistry (way too applied from a mathematical perspective) but the mention of "at midday sun" might indicate that the "mixing" actually included a first, slightly endothermic reaction where two or more of the ingredients reacted with each other.

[alhoon]

I wouldn't trust anything a Greek says!
(It's not racist, I am a Greek; point is it was a state secret and in order to protect it leaving erroneous or impartial recipes would help).

Also it's good you didn't try that recipe, because (and I kid you not) it has a good chance to explore in your face and set you on fire. Naptha is too risky to meddle with. I would offer a safer substitute but I am not sure it is permitted.
Rock salt draws moisture from the air and with CaO included? It would start the reaction by itself.

To give my completely ad-hoc answer to one of your questions: CaO + water creates enough heat for the Naptha to ignite. And when Naptha ignites, the heavier compounds (resin, asphalt) would too and Sulphur and the other stuff will give greater temperature to the flames. Enough to set your own flesh on fire. And if that happens, while you're in contact with the resin and other polymers, the reaction would be fueled by the oxygen in your skin to a degree, so immersion in water may not be enough. Let alone the hydrophobic sticky ingredients that will stick on you.
That's similar to how napalm fluid sticks on you and sets you on fire.


As a note, non-stabilized naptha may explode by itself without you doing anything. That recipe would kill half the people working on such compounds soon enough. Acetone may or may not help to dissolve the sticky substance and so would strong alcohol. By they are both flammable.
What I mean is that if you're hit by what you describe here, there's a good chance that only sand or amputation would save you. No water, no alcohol.

We got to have made a safer substance for warfare. If we used that, half our ships would be on fire before the battle began.
Unless the mix was made properly a few minutes (or seconds) before firing. And it still leaves the question of the over-heated siphons that would make the next batch explode.
Frankly, you don't need only the recipe, you need the people that know when and how to mix that, and the machinery to use it properly.

Are any such ship siphons remaining today?

[Magister Militum Flavius Aetius]

I think fragments of one survive.

And Byzantine accounts record knowledge of how to use it was compartmentalized - the Bulgars captured a warehouse of the stuff, and some siphons and siphon-operators, but still weren't able to utilize it.

Yeah, they had liquid "Zakynthian Asphault" so not pure naptha, but it would have to be collected at specific times of year according to Karatolis' "Greek Fire and its contribution to Byzantine might."

The primary sources, as I posted above, record that it had a tendency to ignite on its own. But once it was stored, oxygen-deprived, in a copper vessel, it was fine. We know the Romans probably heated it in bronze siphons before use.

As for extinguishing it:

"In addition, as numerous writers testify, it could be extinguished only by a few substances, such as sand (which deprived it of oxygen), strong vinegar, or old urine, presumably by some sort of chemical reaction"

[alhoon]

Vinegar would work with what you describe.

Thing is, what you suggest would be very dangerous if the copper vessel got heated by the Mediterranean sun on a vessel and then oxygen was leaked.

[Magister Militum Flavius Aetius]

I think the secret to Greek Fire mustn't have been its active ingredient, but the stabilizing compound.