Jor
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Sodium metal and thiocyanate?
Today I took a small piece of sodium and added a small spatula of potasssium thiocyanate (KSCN). I heated the test tube, and the KSCN melted, and at
that point a very violent reaction started, and quite some white smoke was produced.
I was wondering what is happening here. The only think I can imagine is formation of sulphide and cyanide, so:
2 Na + KSCN --> Na2S + KCN
Is this right ?
If so, it might be a valuable method for producing cyanides, although the reaction is violent and possible cyanide smoke was produced. My fume hood
sucked it all towards the skye, but I used very small amounts (MAX 10 mg of cyanide was produced, if at all this reaction is right). Im not wanting to
produce the stuff, but as many of you do want it, and the starting materials are not really expensive, it might be worth looking into. But the
violence of the reaction might be a problem.
Afterwards, I added some bleach to destroy possible cyanides and sulfides. There were few very small pieces of black material floating arounds, wich
are probably carbon.
Maybe one should try the reaction with other strong reducers like magnesium and zinc. I will soon try zinc, I just bought some.
[Edited on 22-11-2008 by Jor]
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woelen
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KSCN is very hygroscopic, so the violence of the reaction may also be due to the presence of hot water. But it is worth investigating this reaction.
A very reliable test for cyanide is the following:
- Add 3 ml of 10% HCl
- Heat until it has a temperature of 50 C or so.
- Stick your nose in the tube and take a big breathe.
- If the result of this is a dead Jor then there certainly was cyanide in the mix 
Another good - and somewhat less destructive - method for testing for cyanide is the following:
- Dissolve a TINY amount of ferrous sulfate or ferrous chloride or Mohr's salt in 10% HCl (must be high grade acid).
- Add a TINY pinch of Na2SO3 in order to assure that the iron is not oxidized to the +3 oxidation state. When you smell the liquid, there should be a
clearly noticeable, but not a pungent smell of SO2.
- Add this liquid to the liquid with the cyanide. At the very low pH, sulfide does not interfere, it does not precipitate with the iron. The amount of
iron should be less than half the amount of cyanide, hence the remark about a TINY amount.
- Dropwise add 3% H2O2. When there is cyanide, then the liquid turns deep blue/green, due to formation of [FeFe(CN)6](-).
This test works well, even in the presence of HSCN. This is because the Fe-SCN complex is labile, while the cyanoferrate complex is very inert. The
only thing is that there should not be more iron, than can be consumed by the cyanide. If there is too much iron, then it will for the deep-red Fe-SCN
complex and that interferes with your test.
This test is a really sensitive test, the color of the [FeFe(CN)6](-) complex is amazingly strong, and this complex also is very stable, even at very
low pH.
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Pomzazed
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| Quote: | Originally posted by woelen
A very reliable test for cyanide is the following:
- Add 3 ml of 10% HCl
- Heat until it has a temperature of 50 C or so.
- Stick your nose in the tube and take a big breathe.
- If the result of this is a dead Jor then there certainly was cyanide in the mix
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lol!
Don't stare at me making fumes... I'm just experimenting with some gas...
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Jor
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I do not have iron salts
The first method will work, but I'll leave that to someone else 
If this reaction works, there will be formation of sulfide.
This can be detected by smell, but I'd rather not try (Mix of HCN and H2S)
I can dissolve the reaction mix in water and detect sulfide with lead(II)acetate. However, please answer my e-mail woelen, before I can get the
lead(II)acetate (I have a question about my PbO there).
Or maybe cobalt forms a very dark precitipate with sulfide? I'm not sure.
EDIT: I just realised that lead cannot work, it will form a precitipate with thiocyanate. Im not sure about cobalt. I should try that tomorrow.
Or maybe I will just add an oxidiser, oxidising the sulfide to sulfur, wich can be detected. However, I'm not sure what oxidisers oxidise sulfide to
sulfur.
By the way, that detection method for cyanide sounds interesting. Maybe I will make some iron salt with my iron fillings.
However, I wonder if its really [FeFe(CN)]- ... Because won't you just get prussian blue. Are you sure it's not some peroxo-complex?
[Edited on 22-11-2008 by Jor]
[Edited on 22-11-2008 by Jor]
[Edited on 22-11-2008 by Jor]
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12AX7
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How can you not have iron salts? There's iron in your *house* for God's sakes...
TIm
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kclo4
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Acidified Copper salt solutions with the addition of Hydrogen Sulfide produce a Copper sulfate precipitate.
So, I'd assume if you mixed Copper chloride/sulfate with Hydrochloric acid/sulfuric acid and then add your mixture to that you'd see the copper
sulfide precipitate out - assuming that there was in fact Na2S in your mixture.
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Jor
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As far as I know, copper also precitipates out with thiocyanate. And it also does with cyanide as CuCN, with formation of cyanogen. I will try some
test in a few days.
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Jor
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As described in first post, I added a small amount of bleach to the reaction mixture, and I let stand overnight. Today I had disposed of it, and there
was, as soon as I shaked it, and put it out of the hood, a strong smell of H2S. This indicates to me that this reaction might seriously work in the
way I thought it would.
Can you woelen, do the experiment, maybe with NH4SCN if thats less hygroscopic, and test for cyanide?
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woelen
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I also tried the experiment. I did the following:
- Take a spatula full of KSCN
- Heat this material in a clean test tube, until it melts and forms a colorless liquid. Initially some water vapor was released, but finally, a clear
colorless liquid was obtained of molten KSCN which is dry. Let the solid cool down and solidify.
- Add a small piece of sodium (appr. 3x3x3 mm3) and heat again.
- The sodium melts and the KSCN also melts somewhat later. The sodium slowly reacts, and the liquid becomes yellow. The sodium slowly seems to
dissolve in the molten KSCN. In the mean time, the test tube was swirled continuously over the flame in order to keep the liquid material moving and
mixing.
- At a certain point, suddenly the reaction becomes extremely violent, the piece of sodium pops out of the liquid and catches fire  . It falls back in the liquid and then it explodes, multiple smaller droplets being
sprayed around, which catch fire again and a crackling noise is produced. I had a kind of fireworks in the test tube
- The fireworks lasted for one second or so and then the reaction was over. A lot of white smoke was in the test tube.
After cooling down, I added water. All solid material dissolved. I obtained a yellow somewhat turbid liquid.
When some of this liquid is added to acid, a strong smell of H2S is produced. So, there definitely is sulfide in the liquid.
I was not capable of detecting any cyanide. The iron-test was completely negative. The liquid remains pale yellow and adding even the tiniest drop of
H2O2 results in formation of a deep red liquid. So, no ferroferricyanide complex is formed at all, all iron immediately goes to the
thiocyanato-complex.
Another test of cyanide is added bleach, which should result in formation of some gas (nitrogen). No gas is produced at all. The liquid becomes pale
yellow and turbid. A lot of sulphur is precipitated.
So, I'm quite sure that no cyanide is made in this reaction. What IS produced is something I must think about. At the moment I simply don't know.
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Jor
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Your observation match mine
I also had a very violent reaction, and then there was no reaction anymore.
Then I had a lot of smoke as well.
I observed a H2S odour.
AND.... by complete luck I came past a reaction with sodium and sodium thiocyanate, in Vogel. Page 1039, when I was reading the copper phthalocyanine
synthesis yesterday in bed (I have a Vogel book).
In Vogel it is described that elements in organic compounds can be detected by heating with Na-metal. They say that it is essential to use an excess
of Na, otherwise nitrogen and sulfur may combine forming NaSCN. With excess Na, NaCn is formed:
2 Na + NaSCN --> NaCN + Na2S
I can tell you that I did not know of this page before. ]
I was doing a whole set of experiments with Na-metal with many materials a few days ago.
I will do some experiments as well tomorrow on this subject.
Maybe I'll try the reaction with a LARGE excess of sodium metal, and see what happens. I must be prepared for fireworks though 
However, it's getting really cold inthe garage now (5 C). WHen I tried to pour some acetic acid, at once all the liquid solidified formign beautiful
crystals 
Imlooking forward to the summer!
By the way , H2S gets on my nerves, I produced a VERY small amount in thsi reaction, and my whole garage stinked, as well as my house as it was in my
clothes...
Besides, I never know the concentration of this stuff by smell.
[Edited on 23-11-2008 by Jor]
[Edited on 23-11-2008 by Jor]
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woelen
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Yes, my lab also gets cold. I have DMSO (melting point 18 C, so very close to acetic acid), and the bottle is filled with a big chunk of frozen DMSO.
This chemical can only be used in summer time.
Be careful with the Na-NaSCN experiment when you use larger amounts of sodium. Keep in mind that scaled up experiments can behave VERY different.
Often, there is an exponential increase of violence of a reaction with linearly increasing amounts of reagents. A cracked test tube, with glass
shattered around and small burning droplets of molten sodium is not fun at all. So, please be careful. Perform the experiment behind a glass wall (you
can buy special hard to break laminated glass, we have such glass in the door of the bedroom of one of our kids).
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Jor
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I think the sash of my hood will do just fine.
I think I will use a smaller amount of KSCN instead of a larger amount of Na.
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indigofuzzy
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Perhaps if you scale down the amount of KSCN, while keeping the amount of sodium the same as before. You'd have the desired excess of sodium metal,
but less danger.
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