Rubidium Oceans

[Souper]

My question is: If we had an ocean of liquid rubidium, and throw a Homo sapien (human) into that ocean at a depth of 32 feet (not before adapting him to any pressure variance of course).....would it cause that human to explode violently?

We know rubidium is reactive with water, and since our bodies are 60% water...yeah...

[KSK]

My question is: If we had an ocean of liquid rubidium, and throw a Homo sapien (human) into that ocean at a depth of 32 feet (not before adapting him to any pressure variance of course).....would it cause that human to explode violently?

We know rubidium is reactive with water, and since our bodies are 60% water...yeah...

Probably. For added fun, any wet body parts would explode first, or at least burn rapidly and painfully. I'm thinking eyeballs and mucous membranes - which conveniently includes most parts of your body that you really care about.

[EdFred]

No moisture in the air?

[QuesoExplosivo]

Rubidium will also react with oxygen in the air, so the whole ocean would be on fire.

[Souper]

Come to think of it.....

[lajoswinkler]

Little would happen, and no, ocean of liquid rubidium would not erupt in classical fire. Alkali metals do not burn like organic material, breaking down and releasing small volatile molecules.

In order to make a flame (in oxygen) of an alkali metal, or any other matter, you need sufficient concentration of vapor over its condensed phase. With sodium, that happens close to 800 °C (boiling point is almost 883 °C). Because burning sodium does not give off enough heat to maintain such high temperatures, the flame quickly dies and is replaced with smouldering which creates ash of sodium peroxide covering the melt. It is truly difficult to set sodium on fire under normal circumstances.

Rubidium melts at 39.3 °C and boils at 688 °C, so the temperature at which its melt will produce flammable vapors is probably somewhere in the range of 500-550 °C. That is also not sufficient, so rubidium will also start smouldering ("metal fire") when you remove the heat source.

At room temperature, rubidium will start a metal fire after a while. It depends on the buildup of heat , quantity of the material, its surface, properties of air.

If we ignore water vapor constantly seeping through our skin, reaction of just molten rubidium with constituents of our skin is basically negligible, and even then, surface products buildup stops further reactions because they aren't soluble in metal or skin. At higher temperatures reductive power of it is way more obvious. For example, a blob of molten and hot sodium will make a hole in your skin, but dry finger touching a just molten sodium (approx. 98 °C) will survive fine.

However, if we include those traces of water, we get a weak reaction forming dense aqueous solution of rubidium hydroxide, which although doesn't react or is miscible with the metal, does react with the skin in the process of saponification. It is a strong base.

Quantities of water escaping our body are very small, so one could survive and even swim in it (density of the melt at melting point is slightly lower than of water in standard contidions), although the movement would be different due to different viscosity.

There would be chemical burns, though. Quite severe ones after less than half a minute. If the man exposes his mouth with saliva, localized violent reaction would occur because of hydrogen burning and extreme injuries would certainly be a consequence.

When you exclude water from the situation, alkali metals do not react violent at all in normal conditions. If you pour water on their smoulderings, hydrogen rapidly develops and catches fire. The lower you go in the 1st group of periodic table, the more violent the reactions are, but it's basically about hot hydrogen and its mixture with air.

So if you plan to jump into a pool of molten lower alkali metals, be sure not to be wet, to close your orifices, to ensure the melt is not hot and to get out ASAP, but chances are you'll get gravely injured.