Sciencemadness Discussion Board

Dangers of sodium, unexpected result

woelen - 28-5-2007 at 11:31

I post this, just as a warning for others, who experiment with sodium. Usually, sodium reacts vigorously with water, and sometimes it even ignites. When sodium is added to dilute acids (e.g. 10% HCl, but also with H2SO4 or HNO3 of similar concentrations), then the reaction resembles that of the reaction with water, but the metal becomes hotter and a dark red glow can be observed. That phenomenon I wanted to put on a video for my website, it actually looks neat. A dancing red globe on the surface.

For this purpose, I put a small piece of sodium (around 100 mg, probably less) in a little broken test tube with some dilute HCl in it (app. 10%). This initially results in a lot of fizzling, but this time I did not get the red glow, but I did get something totally different :o . Play the movie with sound on!

Movie of the sodium in dilute HCl experiment

Nice to have this on video, but regard it as a warning, when experimenting with sodium. Fortunately nothing bad happened, but droplets of liquid were blown out of the tube, more than 1 meter high :o.

[Edited on 28-5-07 by woelen]

woelen - 28-5-2007 at 12:39

After the initial excitement, I extracted the moment of explosion from this video. This is quite remarkable. The explosion is not in the tube, but above the tube:

chemoleo - 28-5-2007 at 13:09

Awesome picture!
I imagine it's a normal hydrogen/oxygen explosion, where the former reached a critical concentration in air, while the flame is coloured yellow by the sodium ions/atoms?
(you can still see the Na in the tube, so it's not atomised and burning NaOH or something)

[Edited on 28-5-2007 by chemoleo]

Dr. Beaker - 28-5-2007 at 15:44

great movie :o. very counter safty...
if you look very cearfully you see that the explossion is indeed that of H2 (probably by spark made by a small burning piece of Na). prior to the blast Na melted - molten Na is much more nasty... not far from Nak. the burning H2 ignites the molten Na that burns rapidly in air. . you can tell this by the fact that after the "boom" no Na remaines, while in the very short duration of which the Na could'nt have been consmed "normally". you can also see white/grey smoke of probably Na oxides/nitride.
I would'nt call it unexpected - you add the heat of dilution of NaOH + heat of nuetralization with acid (that itself if exothermic enough to boil the solution) and add the heat of the reaction of Na. what did you expact?

p.s you can also try to put Al foil + some mercury in soft drink bottle with HCl 10%. very exciting (and also very foolish /dangerous to do).

[Edited on 29-5-2007 by Dr. Beaker]

garage chemist - 28-5-2007 at 23:48

Woelen, try adding a piece of sodium to hot (near-boiling) water in a beaker. It instantly catches fire, just like potassium.

Our teacher demonstrated the reaction of sodium with conc (37%) HCl to us- it didnt ignite. The interesting thing was that NaCl is nearly insoluble in HCl, so a fine precipitate of NaCl sank to the bottom of the beaker where the sodium reacted.

Zinc - 29-5-2007 at 04:06

A very nice (and dangerous) thing to do is to add molten burning Na to water. It explodes instantly when it touches the water and it explodes much stronger than the explosion of cold Na/water. A piece of sodium (cold) exploded in a glass beaker and it didn't harm the baker. A smaller piece of hot sodium destroyed the beaker completely.

The_Davster - 29-5-2007 at 05:38

I liked the video Woelen(and also the micro-glassware:)).

There is a frame just after the explosion where there are water droplets in the air above the tube, and a orange fire in the bottom of the tube from flaming sodium. I had initially thought that the sodium was consumed in the bang, but it was still burning a couple frames after the bang.

phj - 29-5-2007 at 07:57

Garage chemist, that's very interesting.
So NaCl is less soluble in HCl(sol.) than NaOH in pure water?

P.S. I thought sodium was less dense than water.:o

YT2095 - 29-5-2007 at 08:46

IIRC, it`s due to the Common Ion effect (or something like that).

and sodium Is less dense than water, that`s why it Floats (for a while LOL :D ).

garage chemist - 29-5-2007 at 09:45

The solubility of NaCl drops with increasing HCl content of the solution. This can be used to recrystallize NaCl: dissolve crude NaCl in water, bubble in HCl, and filter the purified NaCl.

It can also be used to liberate acids from their sodium salts: for example perchloric acid is mostly made by adding NaClO4 solution to concentrated HCl, filtering the precipitated NaCl, and distilling away HCl and water from the HClO4.

Of course Na is less dense than water, but the NaOH generated does of course go into the water.

The experiment with hot water and sodium looks very interesting too, and is much less dangerous than sodium and cold water since the hydrogen instantly catches fire and there is no time for an explosive H2/air mix to form.

Sodium and Cold water

chemkid - 29-5-2007 at 14:14

I was thinking of making sodium from electroylisis of sodium hydroxide. then reacting the sodium with water - cold water.

I would be doing this on a realitvely smalll scale 1/2gram or so of sodium, is this a reasonably safe thing to do?

Chemkid

woelen - 29-5-2007 at 23:24

No, this is not safe at all. Making the sodium from the molten sodium hydroxide is a dangerous thing. You need a metal crucible (a metal tin could work OK) in which the NaOH is melted and then you must perform the electrolysis, using an inert atmosphere. The molten Na otherwise will catch fire immediately.

Adding half a gram of sodium to water already gives a VERY violent reaction. I did the experiment with less than 100 mg (and probably much less, I did not weight the piece of Na) and then you already see what can happen.

When experimenting with energetic materials, use only tens of mg quantities, hundreds of mg's already can give rise to nasty accidents.

chemkid - 7-6-2007 at 13:08

Are there any other resonable methods for making sodium in the home lab?

woelen - 7-6-2007 at 13:21

Very hard. Electrolysis of molten salts is an option, but really hard to do and requires good equipment and very severe safety measures.

Another option is synthesis of sodium azide (NaN3), followed by thermal decomposition of this chemical. This also is a difficult process, and requires many intermediate steps, such as making hydrazine. Also this route is not something for the starting home chemist. Do a search over here on sciencemadness (on hydrazine and azide) and you find a few threads on this subject. Nice reads and something which can be done at home, but it requires quite some experience, equipment, and knowledge. Not something to start with.

vulture - 7-6-2007 at 13:33

Quote:

and then you must perform the electrolysis, using an inert atmosphere. The molten Na otherwise will catch fire immediately.


I'm afraid I have to disagree here. My sodium didn't catch fire whilst electrolysing NaOH. There was quite a nasty amount left which gave me quite the scare when I disposed of the NaOH.
The greatest danger of this procedure is the fact that you are producing a mixture of hydrogen and oxygen gas at >300C. This leads to some spectacular effects. Read: Loud explosions and flying droplets of NaOH.

But please continue this discussion in the appropriate sodium thread.

squizzy - 26-6-2007 at 04:11

Hi woelen
I wanted to ask you something unrelated to the actual sodium process.

Relating more to your photographic technique.
What equipment were you using to film and capture the single frame.
Camera, lighting, post production tools
Its fairly good clear photography no frame flutter or artifacts left over from the video process.
Anyway its a great picture shows the sodium yellow ions in the flame.

Thanks
Squizzy

Jdurg - 27-6-2007 at 07:48

I got a chance to see the coolest thing the other day. A buddy of mine works for a company that does a lot of work with the lighter alkali metals (sodium and lithium). They go through so much lithium and sodium that they order it by the pound. Typically five pounds at a time. Have you ever seen and/or held a five-pound brick of sodium? It is amazing. When they need some Na, they just crack open the drum it's stored in, open up the resealable bag and take a chisel and hack off whatever they need. The Na is then taken into a dry box and the outside shaved off to give them a nice, clean sample of Na. I didn't get a chance to see the Li bricks as they weren't using them at the time so I didn't get a chance to see it. I REALLY wanted to get a photograph of me holding the five pound brick of Na, but because it's a competitive research field there are no cameras allowed in the property. :(

DrP - 27-6-2007 at 08:27

QUOTE"droplets of liquid were blown out of the tube, more than 1 meter high ."

A some people in my reaserch lab when I was at uni were using group one metals as catalysts for a wurtz synthesis of polysiloxanes. One of their shared fume cupboards got a bit untidy so one guy decided to clean it out. He rinsed out one of the test tubes he found at the back of the cupboard under the tap. THANKFULLY the test tube did not break when the piece of potassium metal in the bottem of it exploded, sending firey potassium up to hit the roof. He did get a couple of spotted burns on his face from the odd sprayed droplet, but was very lucky I think.

Strangely - no one owned up to being such an idiot as to leave this metal lying arround in a discarded unlabbled test tube in a shared area! Very dangerous.

woelen - 28-6-2007 at 00:31

Quote:
Originally posted by squizzy
Hi woelen
I wanted to ask you something unrelated to the actual sodium process.

Relating more to your photographic technique.
What equipment were you using to film and capture the single frame.
Camera, lighting, post production tools
Its fairly good clear photography no frame flutter or artifacts left over from the video process.
Anyway its a great picture shows the sodium yellow ions in the flame.

Thanks
Squizzy

I use a Canon Powershot 620 for the videos I make, at 640x480 at 30 frames per second, or at 320x240 at 60 frames per second.

For still pictures I prefer the use of my Pentax Optio S. The latter has better macro properties (strong macro can be achieved at relatively large distance, resulting in less perspective distortion, less fish-eye effect).

The light, used in this video is daylight, diffused by a light grey sheet. The beaker itself is placed on a large sheet of white paper.

Still pictures, I scale down with GIMP: http://www.gimp.org

When I have an AVI movie, then I use VirtualDub: http://www.virtualdub.org/

With VirtualDub you can easily extract single frames from an AVI movie. With GIMP you can do slight postprocessing if necessary (mainly correcting a little bit for underexposure or overexposure). I really like the AVI's generated by the Canon Powershot camera, it is LARGE, but has very few artifacts. With VirtualDub, I compress such AVI's, using an MPEG 4 codec.

Unfortunately, the audio capabilities of the Canon Powershot are close to crap. It has very good image and video quality and apparently the designer's budget was used up and for the audio some useless crappy noisy 8-bit hiss was left. You need an external audio recording device. A decent PC audio board is very useful for this.

I use audacity for audio post processing (noise removal): http://audacity.sourceforge.net/

VirtualDub is used for synchronizing an external audio source (in this case a WAV file) with the AVI video. I discard the internal audio track of the Canon Powershot.

Altogether it is quite some work to make a good AVI, when also audio is needed. Most of my AVI's don't have sound, but for some of them, such as this one with the Na-metal, the sound is important.





[Edited on 28-6-07 by woelen]

Engager - 1-7-2007 at 03:03

Sodium/water and Potassium/water explosions not impress me much, after i've tried to drop about 2g of metallic cesium into water. It was drowned and emidately exploded, blowing my glassware to ashes.

There is no reason to make metallic sodium at home, it is very cheap and can be easily bought from chems supplier. I store at home 500 gramm brick of sodium, whitch costed me about 3$ =)

By the way, someone has any idea how can i make Rb and Cs at home conditions? I have around 1.5 kg of rubidium nitrate and about 500g of CsNO3, i've heard that less active alkali metall can replace more active in it's flourides and hyroxides. At least for KF/Na equilibrium constant at 400C is around 4. Is that possible to use potassium metall + RbF mixture to produce metallic rubidium?

Pyrovus - 1-7-2007 at 06:43

A trick used to produce potassium by reduction with sodium is by reacting sodium with molten KCl:

2Na(l) + 2KCl(l) -> NaCl(l) + K2(g)

The reason why this works is because at the temperatures of molten potassium chloride, the potassium formed is a gas, which can be continually removed, shifting the equilibrium to the right.

The other alkali metals have lower boiling points than potassium, so this technique should work for them too.

12AX7 - 1-7-2007 at 06:46

Seperating alkali metals is typically a bad idea. They don't distill apart very well. As long as you have the pure salts, you might as well react them with, say, calcium metal (obviously not directly with the nitrate!) as Ca + Cs2O (or 2 CsOH) = CaO + 2 Cs(g) [+ H2O]. I believe that was what Fleaker was going to do.

Tim

Fleaker - 1-7-2007 at 20:41

Except I am using cesium and rubidium chloride with calcium powder to reduce it. The CsCl and RbCl were a gift of sorts from a board member here. I plan on doing the reduction using a tube furnace. The metal must be distilled out of the stainless 316 reaction tube under high vacuum, at about 640C.


The sodium displacement works for potassium, but not so well for Cs and Rb because your Cs and Rb are usually very contaminated with sodium vapor, as sodium has a high vapor pressure at those temperatures.

@Engager, send me a U2U, I'd be interested in buying some of your Cs and Rb salts and talking about making those metals :) You must live in a good place if you can get Na by the half kilo block for so cheap. I spent about 300 USD for just under 5 kilo grams.