Sciencemadness Discussion Board

Flammable gas from TCCA and bleach!

woelen - 16-6-2013 at 07:05

I did a little experiment with pure TCCA and bleach (appr. 13% active chlorine). I put appr. 4 ml of bleach in a clean test tube and added a few pea-sized pieces of solid TCCA to the bleach, which I crunched into somewhat smaller particles before adding to the bleach (not a fine powder, the particles still were 2 mm or so). When this is done, no reactions seems to occur, but after a while, there are tiny bubbles, formed at the pieces of TCCA. I warmed the test tube with my hands and this makes the reaction run somewhat faster. Slowly, the reaction goes faster and faster and at a certain time, there is a nice (not violent) production of gas in the test tube and the liquid becomes warm, but no so hot that touching it becomes painful.

The gas is colorless, the liquid becomes nearly colorless (the pale yellow color of the bleach disappears). I loosely covered the test tube with some paper tissue until the production of gas became slow again. After that, I kept a flame near the open end of the test tube. This causes a pale flame to flash into the test tube and produces a kind of popping/whoosh noise, very similar to the sound when hydrogen gas in a test tube is ignited. I think that the test tube held a mix of a flammable gas and air. The gas mix has a strong choking smell.

I again am quite surprised to see that a flammable gas is produced from such a strongly oxidizing environment. A previous experiment with solid formamidine disulfide dinitrate (made from thiourea, H2O2 and dilute HNO3) to which bleach is added has a similar effect. This is the second example of a reaction of hypochlorite with an organic compound, which produces a flammable gas. In this case, the organic compound itself also is strongly oxidizing.

As a final test, I added a little HCl (30%) to the resulting colorless liquid, left over from the TCCA + bleach. When this is done, the liquid becomes intense yellow/green and chlorine is produced (pale yellow color of gas mix above liquid, gas is non-flammable).

What could the colorless flammable gas, produced from TCCA and bleach be?

unionised - 16-6-2013 at 07:28

Interesting.
I wonder if you had a mixture of N2 and NCl3
The pop isn't combustion, but explosive decomposition.

TCCA is an acid and acids with hypochlorite and chloride can liberate chlorine. TCCA can also hydrolyse and give ammonia.
Ammonia and Cl2 can give N2 or NCl3 depending on the conditions.
NCl3 has a choking smell.

woelen - 16-6-2013 at 10:44

A mix of N2 and NCl3? I have serious doubts that sufficient NCl3 could be present in the gas-phase to have an explosion. If there would be sufficient NCl3 in the gas phase, then I certainly should have seen yellow oily drops as well. I, however, just had a clear colorless liquid (like water, slightly opalescent) and a colorless gas. So, I am not really convinced that this effect is due to NCl3.

Of course, it could have been explosive decomposition of the gas. Another possibility is very fast combustion of a gas/air mix (I have had this effect many times with mixes of H2 and air).

papaya - 16-6-2013 at 10:52

Is it possible you made hydrazine some way??

DJF90 - 16-6-2013 at 11:11

Could you be making HOCN in some way? It can be made by high temperature decomposition of cyanuric acid, but in the presence of hypochlorite it may form more readily? Other potentials may be cyanogen or cyanogen chloride. In any case, please be careful with this, especially until you know what you're making.

BrominatedSicariidae - 16-6-2013 at 11:28

The first thing that came to mind was phosgene, but that's a complete guess.

I can't think of a useful chemical equation—even assuming some hydrolysis of TCCA to CYA to then react with ClO(-), which I would suppose is :

2(HNCO)3 + 9ClO(-) ---> 3N2 + 6CO2 + 9Cl(-) + 3H2O

And none of those products fit your description at all.


[Edited on 16-6-2013 by BrominatedSicariidae]

woelen - 16-6-2013 at 11:50

@papaya: Hydrazine is not what I made. I have pure hydrazine hydrate and this stuff's vapor is not flammable and it certainly does not explode when a flame is kept near it.

@DJF90: I work with small quantities (pea-sized pieces of TCCA and a few ml of bleach). Besides that, I use a well-ventilated place, so little chance of poisoning myself.

@BrominatedSicariidae: Phosgene could not be one of the products. It is not flammable, and it hydrolyses in contact with the somewhat alkaline solutions of bleach.

It is remarkable that a reaction between two OTC chemicals gives such remarkable results. Of course, this reaction has no practical meaning at all, but from a theoretical and academic point of view I find it rather interesting! I also did a search on internet, but I could not find any useful reference about the reaction between hypochlorite and TCCA.

papaya - 16-6-2013 at 14:29

I can suggest you to do 2 more experiments woelen:

1. cyanuric acid + bleach (if this works then urea+bleach, but which we know generates hydrazine) to see if the TCCA role is unique
2. TCCA + NaOH (generate bleach in situ?)

Btw, how it smells? I think chloramines, and is there any information on NHCL2 and NH2CL flammability?

I hope you will find the solution at the end and share with us :)

BrominatedSicariidae - 16-6-2013 at 14:49

I believe that TCCA plays a special role.

My previous hypothesized equation was actually correct; I found a paper about it, maybe it will help you:

http://jspsi.poolhelp.com/ARTICLES/JSPSI_V4N2_pp23-28.pdf

[Edited on 16-6-2013 by BrominatedSicariidae]

[Edited on 16-6-2013 by BrominatedSicariidae]

woelen - 16-6-2013 at 23:13

I have been thinking of NH2Cl myself. This is a colorless gas, but it is said to be very unstable at high concentration and according to wikipedia it decomposes violently above -40 C when in the pure state. From this I at first dismissed it, because my mix is +40 C and probably even warmer instead of -40 C. But wikipedia can be wrong, maybe NH2Cl is more stable than the article suggests.

NHCl2 is a yellow gas, I do not think that this is the gas formed in my experiments. The gas I made is colorless, even when viewed through the full length of the test tube. This matches the description of NH2Cl.

I am notsure about the flammability of NH2Cl though. I have expeirmented with gaseous NH3 and this is not really flammable. It can help sustain a flame, but it needs another source of fire (such as a burning wooden stick) to burn. If the source of fire is taken away, then the ammonia gas also stops burning. I would expect NH2Cl to be less flammable than NH3, this in analogy to CH4 and CH3Cl. The more chlorinated, the less flammable.

papaya - 17-6-2013 at 00:11

But you can't compare NCL3 with CCL4.. Also even NH3 doesn't burn in air, it must burn in oxygen and maybe in chlorine also? (I don't see why NH3 will form under these conditions). Anyway, what is your next experiment?

woelen - 17-6-2013 at 00:30

First to take some confusion away, I did not do the experiments with gaseous NH3 as part of this series of experiments and I see no reason why NH3 would be formed in the reaction between TCCA and bleach. It is an experiment which I did a long time ago and which I just mentioned in order to demonstrate that I expect NH2Cl to be even less flammable than NH3, which already only is marginally flammable.

My next experiment will be reacting hypochlorite with ammonia. This reaction is said to lead to formation of NH2Cl and then I'll try to ignite this mix. Maybe I find the time to do this experiment this evening. If igniting the gas mix from this reaction leads to a similar effect, then that is strong evidence for formation of NH2Cl from TCCA and bleach as well. If it only leads to non-flammable gas, then it does not say very much, NH3 + bleach might just give N2 with a very small amount of NH2Cl, I never tried that before.

I understand that one cannot simply compare chlorinated derivatives of CH4 with chlorinated derivatives of NH3, but such a comparison _may_ help somewhat in assessing flammability. CH4 is more flammable than CH3Cl and that in turn is more flammable than CH2Cl2. I think it would not be very strange if NH3 would be more flammable than NH2Cl and because NH3 cannot burn in air alone, I would expect NH2Cl also to be uncapable of sustaining a flame in air. But maybe it decomposes violently when ignited and then there is no real burning, but decomposition. If there is indeed decomposition, then this decomposition must be very violent, it is accompanied with a flash of light moving inwards, like a flame-front of a flammable gas/air mix.

Finnnicus - 17-6-2013 at 00:41

Doesnt the incredibly flammable hydrazine form from NH4OH and NaOCl?
Directly: 2NH3 + NaOCl --> N2H4 + NaCl + H2O.
Or from chloroamine formed in situ: NH2Cl + NH3 --> N2H4 + HCl

I am most probably wrong. Please correct me.

woelen - 17-6-2013 at 02:14

Hydrazine is not incredibly flammable under the conditions of this experiment. I have pure hydrazine hydrate (N2H4.H2O) and when a flame is kept near this liquid, then nothing happens. Pure anhydrous hydrazine is flammable (and dangerously explosive), but this never can form under the conditions of the experiment I performed.

There is a big difference between anhydrous hydrazine and the hydrate. The latter is quite reactive, but it is much more stable than the former. The hydrate is a true chemical compound, it is not just a mix of water and hydrazine, it is a compound with precise formula N2H4.H2O.

[Edited on 17-6-13 by woelen]

woelen - 17-6-2013 at 10:23

I did the experiment with NH3 + bleach. I tried two variations.

In one experiment I used excess ammonia (32% NH3) and added the bleach (13% active chlorine) to the ammonia. This produces only a little amount of colorless gas, nothing flammable, no really interesting things. The gas is odorless, it only has a smell of ammonia (due to the excess).

In the other experiment I used excess bleach (13% active chlorine) and added ammonia (5% NH3) to the bleach. This produces much more gas. The gas mix has a pungent smell, most likely due to a decent amount of NH2Cl. The gas mix is not flammable though.

Finally, I did a third experiment, adding TCCA to excess of 5% ammonia. This produces a lot of gas and white smoke. The gas mix is not flammable. WARNING: Do not repeat this experiment with more than 15% NH3. When TCCA is added to 15% or higher concentration of ammonia, it explodes!

So, this set of experiments is not really conclusive. The gas mix is not flammable. Most likely this is due to the presence of N2. I think that only a small amount of NH2Cl is formed in the second experiment.

[Edited on 17-6-13 by woelen]

papaya - 17-6-2013 at 11:00

Wouldn't you try what I suggested above ? Also in your original experiment you said that test tube became hot, may it be that whatever is flammable there needs to go into vapor phase first?

woelen - 17-6-2013 at 12:35

I did both of your experiments.

-------------------------------------------------------

One experiment is adding TCCA to NaOH. This experiment indeed yields the flammable gas, but getting some of this gas is harder than with bleach and TCCA. When solid TCCA is added to solid NaOH and some water is added, then vigorous production of a colorless gas starts and the reaction goes faster and faster. A runaway occurs. The gas is inflammable (I think it is N2).
The experiment was repeated, but now with much more water, such that the liquid does not heat up too much. In this case, no gas was produced and hardly anything happened. I slightly heated the liquid, such that it became a little warmer than my hands. Slow production of gas started and again, the reaction became quicker over time, but it never became violent. This gas mix was flammable, but not as much as in the experiment with bleach and TCCA.
I tried a few other variations, but I at most managed to get a somewhat flammable mix, but never obtained a real pop/whoosh sound. But the fact that some flammable gas is produced is sufficiently convincing for me. This flammable gas almost certainly is the same as in the bleach experiment, but mixed with N2.
Another important observation is that the liquid is totally clear and colorless. Absolutely no oily drops can be observed, nothing at all.

--------------------------------------------------------

The other experiment is adding isocyanuric acid to bleach. This experiment does not give any interesting results. The isocyanuric acid partially dissolves and gives a turbid white liquid like milk. On gentle warming, some gas is produced with a lot of foam. I allowed the test tube to be filled with most of the gas/foam and then struck it, such that most of the foam breaks and then kept a flame near the open end. No flame at all, nothing flammable. The gas simply must be N2.

--------------------------------------------------------

And what is the conclusion of these experiments? I think TCCA is essential for the formation of the flammable gas, and hypochlorite is needed as well. With NaOH first hypochlorite is formed and with excess TCCA the flammable gas is produced. With NaOH also a lot of cyanurate goes into solution and this produces N2 with hypochlorite. So, it is understandable that TCCA with NaOH gives a mix of N2 and the flammable gas and the result is weaker than with bleach and TCCA.

papaya - 17-6-2013 at 13:57

Yes, I also think that the only conclusion here is that TCCA is necessary here (but it's weird, since only organic comes from 'cyanurate' moiety) or maybe the reaction of cyanuric acid with NaOCl must be done in highly basic medium (highly doubt). Well, before all these reaches the dead-end I'm going to postulate a stupidest idea: the gas is CO ? :o how can one test for CO?
EDIT:
I pondered a bit and correct me please if I'm wrong, but the structure of cyanuric acid is different from TCCA because of tautomery. I mean, TCCA is the keto form while the acid (and salts) is in eno form with aromatic cycle which must be harder to break that's why the reaction doesn't work with acid. Is this my second stupid idea in a single post?
2: Is your TCCA pure? Why not to recrystallize it from acetone?
[Edited on 17-6-2013 by papaya]

[Edited on 17-6-2013 by papaya]

BrominatedSicariidae - 17-6-2013 at 19:59

I doubt it is CO because woelen said the gas mixture had a "strong choking smell," and CO is odorless.

It could possibly be some isocyanate; many R—CNO (such as HCNO) compounds are used as explosives, and (if they smell anything like HCN) then it would also explain the smell.

As mentioned previously by DJF90, it could also be HOCN, but I believe that is an isomer of the former.

[Edited on 18-6-2013 by BrominatedSicariidae]

[Edited on 18-6-2013 by BrominatedSicariidae]

woelen - 17-6-2013 at 22:47

The TCCA is pure. The bottle says "92% active chlorine" and this is near the theoretical value for 100% pure TCCA.

I also have severe doubts about CO. CO is strongly reducing and how could such a gas be formed in such a strongly oxidizing environment? I myself tend to believe more and more that it is NH2Cl, but unfortunately very little information can be found about this compound. Most information is about swimming pools and about water treatment with very dilute solutions of NH2Cl, but of course that information does not tell anything about flammable or explosive properties of the more or less pure gas.

The smell of the gas mix is really bad. It is not as strong as the smell of chlorine, but its strength comes close to it (the actual smell, however, is quite different from the smell of chlorine). You must very carefully whiff some of the gas to your nose and certainly should not stick your nose in the test tube. If you do that, then you'll certainly get the mother of all caughs.

I can imagine formation of NH2Cl from TCCA as follows:

TCCA contains -N(-Cl)-C(=O)- chains. These could hydrolyze to NH2Cl and H2CO3, but normally this does not occur. The oxidizing nature of the hypochlorite may lead to oxidative breakage of the ring and then the above mentioned hydrolysis may occur. At the same time, part of the N-atoms must end up in oxidized species, most likely N2. The -C(=O)- part would end up in carbonate ion, while the -N(-Cl)- part hydrolyzes and picks up hydrogen from water, the OH-group from the water then goes to the -C(=O)- part and becomes part of a (bi)carbonate ion. So, the gas produced would be a mix of N2 and NH2Cl, with at least one molecule of N2 for 4 molecules of NH2Cl, but probably more of the N-atoms are oxidized and a larger part of the nitrogen ends up as N2. What remains behind in solution is carbonate ion and chloride.

Cyanuric acid does not contain -N(-Cl)- parts. Its triol-form contains -N(-H)- parts and its triketol-form contains aromatic -N-C-N chains. I can only imagine oxidative cleavage of the ring structure to occur with formation of N2 and hydrolysis to NH3 and carbonate ion. The NH3 then immediately is destroyed by excess bleach and nearly all is converted to N2.


[Edited on 18-6-13 by woelen]

BrominatedSicariidae - 18-6-2013 at 04:01

Could you possibly find the molar mass of the gas being produced?

AndersHoveland - 18-6-2013 at 04:02

Quote: Originally posted by woelen  
In the other experiment I used excess bleach (13% active chlorine) and added ammonia (5% NH3) to the bleach. This produces much more gas. The gas mix is not flammable though.

Finally, I did a third experiment, adding TCCA to excess of 5% ammonia. This produces a lot of gas and white smoke. The gas mix is not flammable. WARNING: Do not repeat this experiment with more than 15% NH3. When TCCA is added to 15% or higher concentration of ammonia, it explodes!

The gas mix is not flammable. Most likely this is due to the presence of N2.

One potential explanation may be that the reaction between bleach and ammonia produces too much nitrogen, so that the NH2Cl is not flammable. If there is too much ammonia, it may likely be reacting with the NH2Cl to transiently form hydrazine, which then quickly gets oxidized, releasing nitrogen gas.

In my experience, NH2Cl is not unstable in the same way that ClO2 is, but rather is chemically unstable. It's solutions in water lose their potency over a short period of time (though I am sure in very dilute solution it stays around much much longer). It is not possible to "saturate" a solution with chloramine gas, it just decomposes and bubbles out as nitrogen.
NH2Cl is less soluble in alkaline solution, and also even much less stable. Good thing the chloramine gas bubbles out, otherwise it would decompose in the alkaline solution.

For flammable gas, some other possibilities are hydrogen cyanide or carbon monoxide, possible products of incomplete oxidation of cyanuric acid, or its partially chlorinated derivatives. Any carbon dioxide would be pulled out by the base to form bicarbonate, so would not contaminate the released gas.

[Edited on 18-6-2013 by AndersHoveland]

unionised - 18-6-2013 at 05:13

You can get an explosion without having anything "!flammable" present
http://www.youtube.com/watch?v=AEYevHGKkgI

so the title of the thread may be misleading.