Alkali + water = boom

[essence_of_cool]

Im no chemistry genius (im more into bio), but...

 

I just spent the last 20 minutes drooling at the sight of idiots placing minute amounts (1-2 grams) of Li, Na, K, Rb, and yes... caesium into bathtube with water. Anyway, big bang.

So how come i cant find a single video with francium! Is francium that reactive that it cant be SHOWN?.

 

I was also thinking, wouldnt it be efficient to make some kind of weaponized version of a francium or caesium bomb, where it contains both the alkali and some water?

 

Anyway, appreciate any responses

[YT2095]

simply because of it`s rarity, in fact there`s only about an ounce of it at any given time on the planet (naturally occurring).

 

it`s also rather radioactive and wouldn`t make for very clever demo!

[CaptainPanic]

Reason: "[Francium... ] is the second rarest naturally occurring element (after astatine).

 

That's already a good reason, but to top it off: "Francium is a highly radioactive metal that decays into astatine, radium, and radon".

 

Two very good reasons not to play with Francium in your bath tub.

[edit] There should be a YT-is-already-answering-this-post-warning in this forum.

[Gilded]

The reason you can't do an experiment like that with even a gram of francium is that it's ridiculously radioactive. It's more radioactive than plutonium, neptunium, americium... The unstability tends to decrease as you go further into the transuranics, and even fermium isn't as radioactive as francium. As francium is so radioactive, it's hard to make a large amount of it as it quickly decays away. If you had an amount of francium visible with the naked eye your naked eye would probably boil off its socket. To put this shortly, francium is too radioactive to use in any chemistry demonstrations like that.

 

If those "idiots" placing alkali metals in bathtubs were the guys from Brainiac at least the cesium was faked by the way. But that doesn't mean a similar effect can't be achieved, they just did it wrong.

 

And no it wouldn't be very efficient compared to conventional bombs. And even if you had a ridiculous amount of let's say cesium you'd be better off using something else than water to oxidize it.

[essence_of_cool]

Wow! i did not know it was that radioactive. And yes, stupid me, i did watch that (stupid and ridiculus) braniac, and i now fell cheap and violated because of it.

 

Thanks that answered my question

[hermanntrude]

Im no chemistry genius (im more into bio), but...

 

I just spent the last 20 minutes drooling at the sight of idiots placing minute amounts (1-2 grams) of Li, Na, K, Rb, and yes... caesium into bathtube with water. Anyway, big bang.

So how come i cant find a single video with francium! Is francium that reactive that it cant be SHOWN?.

 

I was also thinking, wouldnt it be efficient to make some kind of weaponized version of a francium or caesium bomb, where it contains both the alkali and some water?

 

Anyway, appreciate any responses

 

These arethe two things which spring to every chemistry student's mind when they see the demonstration. The demonstration should really include a breif talk about francium. Also see this link, which explains why the explosion actually gets LESS big after sodium and potassium...

[jdurg]

Yeah, I think every person who works in chemistry, or has an interest in chemistry, has wondered "Gee, wouldn't it be cool to see cesium in water? Or even better, francium?!" Once you learn a bit more, however, you realze that the relationship between the metal and the explosion isn't a linear one down the table.

 

Theodore's explanation is a great one and all introductory chemistry folks should read it. There are also other reasons that aren't explained in as much detail.

 

Cesium has a melting point just above room temperature. If you live close to the equator, it's melting point is probably below room temperature making it a liquid. (A very beautiful, golden liquid, however. ;D ) Cesium, however, is also denser than water. Even when liquid. So if you throw the Cs into a lake, it will sink to the bottom while also reacting. Inside water, there isn't a whole lot of oxygen. So while it's happily producing hydrogen gas, the H2 can only ignite when it reacts with O2. All the reaction you see is of that which is close to the surface. If you use a substantially large sample, most of it will likely sink down quite a bit and just produce H2 under water and not real big KABOOM.

 

I took a full ounce of sodium metal, attached it to a rock with some string, and threw it in a lake. The rock sunk, we saw some bubbles of H2 come up, but nothing else happened. So the water was able to prevent a massive reaction with O2 and hence a fire/explosion.

 

You'll still see a small boom with Rb and Cs, I'm guessing, because the reaction happens so quickly and with so much heat generated that water will vaporize instantly and flash boil. But with Na and K being less dense than water, they happily float on the water while generating lots of heat and H2 which can easily mix with atmospheric O2, hence the large KABOOMs.

 

Francium, if it could even be isolated, would probably be a liquid, if not close to one, just based on the trends in the column. I haven't actually investigated that though. Still, the insane radioactivity of it which has been detailed here in this thread, would cause the Francium to boil away if it were ever isolated. It would then rapidly react with atmospheric air and oxygen and never have a chance to see water (which the heat the radioactivity is creating would probably vaporize before it touches the metal surface).

[swansont]

Oh, you can make Rb go boom. I've been working with alkalis for almost 20 years (they are the easiest to laser trap because of their simple state structure). There was one time we were cleaning out the oven used to create a Rb atomic beam, and thought all of the macroscopic bunches of Rb were gone. The oven was basically a pipe with a small hole in the side and a removable top; you'd drop a 5g ampoule inside, put it in a vacuum chamber and pump out the air.

 

Well, the last time we had filled it, our postdoc had crushed the ampoule while trying to pop the top off (after scoring it with a glass cutter; he apparently didn't score it well enough) So there were a few small bits of glass in the oven, and some Rb was hiding underneath. When we dumped some water in to scavenge those last few atoms, it turned into a cannon and shot the glass into the side of the fume hood.

[jdurg]

Yeah, I would think that smaller bits of Rubidium/Cesium would have a greater chance of making a larger "boom" than a bigger chunk. Though, I think the best reaction would be to crack open some Rb or Cs, then pour the water onto that. You'll have a large amount of H2 produced very fast due to the large surface area, plus there would be plenty of O2 around to ignite the H2. That would probably be much more impressive than taking a chunk and dropping it into some water.

[frosch45]

One thing that would be cool to expiriment with would be some Rb or Cs powder (obviously has to be ground up in an inert atmosphere and stuff). Its too bad that it is even so reactive in air

[YT2095]

I disagree on the grounds of What would you then do with it?

 

you can`t take it Into air to use it as it would just flash off instantly, and if you maintained the inert atmosphere and put it into water it would just give off H2 and that would be it.

 

small chunks (a few Milligrams) would be better than a powder for a demo IMO.

[Gilded]

Plan: Buy a 250g ampoule of cesium, go outside when it rains, throw the ampoule in the air and smash it with a baseball bat.

[frosch45]

I disagree on the grounds of What would you then do with it?

 

you can`t take it Into air to use it as it would just flash off instantly, and if you maintained the inert atmosphere and put it into water it would just give off H2 and that would be it.

 

small chunks (a few Milligrams) would be better than a powder for a demo IMO.

 

I understand what you are saying; I wasn't saying that it was practical. It would have been interesting, however, to see the result.

 

Oh well

[jdurg]

It would be damned near impossible for cesium. With a melting point just above room temperature, it would probably melt together to form larger globs in a heartbeat. I would think the act of making a powder with it would cause it to melt together. (Unless cryogenic temperatures were used, but even then the friction generated would raise it above it's MP).

[big314mp]

You could do it while pouring liquid nitrogen over it, as that keeps it cold, and under an inert atmosphere all in one fell swoop.

 

What could be interesting (since I'm on that train of thought) is chucking the cesium powder in a small vat of liquid oxygen.

 

On a side note, if you use a concentrated, strong acid instead of water, does the reaction progress significantly more violently?

[YT2095]

if you use a concentrated, strong acid instead of water, does the reaction progress significantly more violently?

 

more heat will be generated, but the same amount of H2 will be given off.

[hermanntrude]

 

I took a full ounce of sodium metal, attached it to a rock with some string, and threw it in a lake. The rock sunk, we saw some bubbles of H2 come up, but nothing else happened. So the water was able to prevent a massive reaction with O2 and hence a fire/explosion.

 

I often thought about doing something like this... particularly now that I have 3 pounds of sodium i want to get rid of... the trouble is that it basically (no pun intended) results in contaminating an entire watershed with sodium hydroxide

[YT2095]

why don`t you cut it up into smaller chunks under oil, put them into separate containers and sell them on eBay, then use the money to buy different elements.

[hermanntrude]

why don`t you cut it up into smaller chunks under oil, put them into separate containers and sell them on eBay, then use the money to buy different elements.

 

is it legal to sell sodium? And it doesn't actually belong to me personally, so even if it is, it isn't

[YT2095]

sorry, I must have misunderstood:

I have 3 pounds of sodium i want to get rid of

sounds like you have 3 pounds of sodium

 

as for eBay sure it`s legal, I`v seen it sold on there by "Shops" as well as private sellers.

[swansont]

is it legal to sell sodium? And it doesn't actually belong to me personally, so even if it is, it isn't

 

It better be. They sell it bound with chlorine at the grocery store.

 

Seriously, though, you can buy alkalis online, so I imagine you can sell them, too.

[hermanntrude]

i suspect you'd need a license of some kind

[jdurg]

No you don't. I got my sodium off of E-Bay, and there are PLENTY of places online that sell it. The caveat is that you MUST ship it as a hazardous material since if you don't and you get caught, you are going to pay some INSANE fines.

[hermanntrude]

No you don't. I got my sodium off of E-Bay, and there are PLENTY of places online that sell it. The caveat is that you MUST ship it as a hazardous material since if you don't and you get caught, you are going to pay some INSANE fines.

 

doesnt mean those places arent licenced, or just doing it illegally

[jdurg]

Regardless, it doesn't matter. You do NOT need a license to posses or sell alkali metals. There is no category that it falls under which require a license for the possession. Licenses are required for explosives, some nuclear material, etc. If you required a license to sell it, you would require a license to possess it. Licenses are required to keep track of the location and amount of a substance. If you don't require a license to possess it, then having a license to sell it is meaningless.

 

If you can show me where it states that you need a license to sell/posses sodium or other alkali metals then I will stand corrected. However, I highly doubt you'll find it.