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wg48
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NaDIC explodes on heating ???
I was checking how dehydrated about 1g sodium dichloroisocyanunric acid was by heating it in a small test tube. Initially it appeared dry then I
noticed what I thought was steam condensing on the upper part of the tube. Then I noticed a change in colour on some of the granules on the hot part
of tube from powder white to grey tinged with orange.
It was no long being heated but it appeared to be in thermal runner way with steam rapidly issuing from the loose cap. I was about to dump the tube
when its contents rapidly decomposed propelling at least part of tube into the side of a small oven.
I had previously dehydrated about 10g of NaDIC at 120C in a small oven with no problems.
I did not know that NaDIC (if that’s what it is) has a tendency to explode (very rapid decomposition) when heated . Perhaps nitrogen trichloride
formed.
Damaged oven, the remains of the test tube is inside
Damaged finger I hope the nail bed is ok
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Chemi Pharma
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I had a similar experience with TCCA, that start to melt and expeled dense fumes inside a blender, while triturating pool tablets to a thin powder.
I was lucky cause I was working inside a fumehood and got to switch the blender power off and the exaustion on, but the plastic of the blender melted
and almost catched fire. The hood were filled full of toxic fumes and I spent more than 10 minutes to clean the air inside it.
Until now, I don't know what happened. May be NCl3 as @wg48 said.
I wish somebody here could explain what can it be too.
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wg48
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Quote: Originally posted by Chemi Pharma  | I had a similar experience with TCCA, that start to melt and expeled dense fumes inside a blender, while triturating pool tablets to a thin powder.
I was lucky cause I was working inside a fumehood and got to switch the blender power off and the exaustion on, but the plastic of the blender melted
and almost catched fire. The hood were filled full of toxic fumes and I spent more than 10 minutes to clean the air inside it.
Until now, I don't know what happened. May be NCl3 as @wg48 said.
I wish somebody here could explain what can it be too. |
The msds say:
"Special Remarks on Explosion Hazards:
Reacts explosively with calcium hypochlorite in the presence of water. May explode from heat or contamination".
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Chemi Pharma
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Thanks @wg48, I know about TCCA MSDS, but I wanna know what's the chemistry behind this behavior.
What happens when you heat TCCA? What chemicals is produced? What chemicals the dense fumes I observed contains? What about the equations?
What have made me astonished is the fact I don't believe triturating pool tablets in a blender less than five minutes produces enough heat to start so
big runaway I saw.
I still need to know more about that.
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wg48
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| Quote: Originally posted by Chemi Pharma | Thanks @wg48, I know about TCCA MSDS, but I wanna know what's the chemistry behind this behavior.
What happens when you heat TCCA? What chemicals is produced? What chemicals the dense fumes I observed contains? What about the equations?
What have made me astonished is the fact I don't believe triturating pool tablets in a blender less than five minutes produces enough heat to start so
big runaway I saw.
I still need to know more about that. |
Yes I would like the details too.
Not much left of the nice Pyrex screw cap test tube and I was going to use one that had maganese oxide burnt on it but I thought that was not a good
idea.
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Vomaturge
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Where did you get the NaDIC?
https://patents.google.com/patent/US4118570A/en
Apparently, NCl3 does form during the production process. Just a wild guess, but maybe your sodium dichloroisocyanurate had some leftover precursors
in it, some actual trichloramine, or some other reactive impurity. In the "description of the prior art" section of that patent, it said
"In the past, it was necessary to further process the SDCC reaction mixture of the above reactions to remove these undesirable quantities of NCl3.
This procedure was time-consuming and costly."
Perhaps the source of your product didn't use the patent, and didn't want to add a "time-consuming and costly" step to their production process.
Instead, maybe they let the NCl3 impurity settle to the bottom of the barrel, and sold it to you?
The reason I would suspect that some precursors were left over in the product is that heating the mix could have completed the reaction making some
more NaDIC, but also more yellow NCl3, which responded badly to further heating.
I couldn't find the heat of formation for NaDIC, making it hard to estimate whether it itself decomposes exothermically.
Does hypochlorite effect dichlorocyanourates, or just tri?
Because if it effects both, an impurity of it could also be the issue.
In any case, sorry to hear about your finger, test tube, and oven, but glad the 10g batch didn't do this... yet.
[Edited on 12-2-2018 by Vomaturge]
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Ozone
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"...white to grey tinged with orange." I'm wondering about Chlorine dioxide (ClO2), maybe (I've noticed it tends to go dark yellow/orange prior to
going kaboom). There are better references, but here is a photo: https://en.wikipedia.org/wiki/Chlorine_dioxide.
Could be NCl3, of course, but it's more yellow, and three times as spooky (blew up a small sample of butylamine, once, this way--best guess at what
happened).
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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woelen
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TCCA (trichloro cyanuric acid) and Na-DCC (sodium dichloro cyanurate) both are very reactive chemicals. For OTC products I find these remarkably
dangerous. I also have experience with extremely violent reactions of these chemicals:
- heating leads to violent decomposition
- mixing with certain organics (e.g. alcohol)
- mixing with ammonia or organic primary amines
- most notably, mixing with hypochlorites
In NL there has been a very nasty accident with Na-DCC some years ago. A certain brand of swimming pool chlorinator sold so-called shock-treatment. It
was granular Ca(ClO)2, appr. 70% active chlorine. This same brand one year later had switched to granular pure Na-DCC. The containers were nearly
identical, same blue label, pool chlorine shock treatment, water-soluble (something like that on a label). To be mixed with water and then to be
poured in the swimming pool. A person had a bottle of this stuff from the previous year, maybe 20% left over, being Ca(ClO)2. He put that in a bucket.
He added a similar amount from a new container, being Na-DCC and then added water. He did this inside. The stuff reacted EXTREMELY violently, giving
off dense choking fumes and the material charred. He could go outside, otherwise he probably would have died in the dense choking fumes.
I have the impression that Na-DCC and TCCA easily form NCl3, leading to explosions. I do not believe that ClO2 is involved in the danger/risk of these
chemicals. These chemicals also react insanely violently with ammonia. Just for fun, add 15% or so ammonia to a pea-sized chunk of TCCA or Na-DCC. You
will be surprised by the extreme violence of this reaction. E.g. sodium with water is tame compared to that.
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wg48
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| Quote: Originally posted by Ozone | "...white to grey tinged with orange." I'm wondering about Chlorine dioxide (ClO2), maybe (I've noticed it tends to go dark yellow/orange prior to
going kaboom). There are better references, but here is a photo: https://en.wikipedia.org/wiki/Chlorine_dioxide.
Could be NCl3, of course, but it's more yellow, and three times as spooky (blew up a small sample of butylamine, once, this way--best guess at what
happened).
O3 |
I need to check, as well as I can, that it is NaDIC and not significantly contaminated or adulterated in particular with calcium beaching powder. I
will not be attempting a melting point test in a test tube on it without blast protection and remote monitoring LOL
It was purchased from a pool chemical suppler on Ebay. I have purchased what was supposed to silica gel but was actual clay and also naphthalene
mothballs that where actual a dash of naphthalene, insecticide and mostly inert filler. So I would not be surprised if it is adulterated.
I will also check that the reaction is reproducible but outside this time in an open metal crucible.
Apparently from Woelen's post it may well be unadulterated.
But I would like to know the safe dehydration temperature for the dihydrate, my small oven works just fine with a door.
[Edited on 12-2-2018 by wg48]
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Chemi Pharma
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| Quote: Originally posted by woelen | | These chemicals also react insanely violently with ammonia. Just for fun, add 15% or so ammonia to a pea-sized chunk of TCCA or Na-DCC. You will be
surprised by the extreme violence of this reaction. E.g. sodium with water is tame compared to that. |
@Woelen, what do you think about this paper I attached below where researchers mix TCCA with ammonea and alcohol, amines, benzyl halides and
aldehydes, as a substrate, to produce nitriles?
Do you think exist a safer way to scale this reaction between milimoles of substrates onto moles?
Attachment: alcohols, aldehydes, amines and benzyl halides to nitriles with TCCA + NH4OH.pdf (115kB)
This file has been downloaded 476 times
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woelen
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I think that this is useful for synthesis of specialty nitriles in small quantities, but when you want to have bulk0production at a mol-scale, then I
see no practical use for this reaction. The authors themselves already state that adding 0.75 mmol of TCCA to the reactants must be done in very small
portions to avoid explosion. If you want to add e.g. 2 moles, then it would takes ages before all of it can be added to the reactants.
The reaction between TCCA and many other chemicals scales badly. Heat-production vs. heat transfer out of the reaction mix scales cubically vs.
quadratically. So, if e.g. 8 times as much heat is produced by taking 8 times as much reactant, then only 4 times as much heat transfer can take
place. This leads to a strong increase of temperature in the 8-fold reaction mix. Things become much worse when larger amounts (e.g. 1000 times as
much) are needed.
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Chemi Pharma
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Thanks for the explanation @woelen.
I believe have found something digging old threads about the products of TCCA decomposition and why it can be so smelly (the fumes) and even
explosive:
| Quote: Originally posted by Formatik | | Quote: Originally posted by halogenstruck | | careful:Hazzard:[heating TCCA]maybe explosive decomposition due to NCl3 prescence although dilution by NaCl reduces the possible danger
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Yes, be cautious dry heating trichloroisocyanuric acid especially with oxidizables. Thermal degradation of it in inert gas is a known synthesis to
carbonyl diisocyanate (colorless liquid which smells choking like SO2Cl2, probably extremely poisonous) alongside some NCl3, to a lesser extent Cl2
and CO2. |
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Ozone
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Hmm. Now that I think more on it, NCl3 (and other nastiness) seems more likely than ClO2.
I've run into a few very stable things that become unstable when rigorously dried--that is, some amount of water (be it crystallization, solvation, or
what have you) stabilizes the compound. For example, sucralose (the sweetener), is so stable some are regarding it as a potential environmental
pollutant. BUT, in it's pure form, it will spontaneously eliminate HCl(g) when bone-dry (in a drybox at rt). This was shockingly apparent when the
bottle was opened and I was gassed with HCl and noted that the product had turned black. Upon opening, some moisture got in there, and the reaction
began to auto accelerate (pressurizing and rounding the square container). Now, this was quenched in a sink full of water and that was that--But, of
course I bought more to try and figure out why I was gassed by a non-nutritive sweetener.
The result is completely reproducible, and can be measured via TGA/DSC and the tar examined via GC-MS. It turns out, the stuff is thermodynamically
stable, but when dry, is entropically unstable--this is why it's heavily diluted onto maltodextrin and kept in aluminized mylar (to maintain moisture
rather than keeping it out). Funny thing is that Tate and Lyle give a melting point for the stuff, the patent indicates that the product was isolated
as a syrup, and said MP (which is impossible because it decomposes) has been parroted ad-infinitum ever since. I suppose a product that decomposes to
yield HCl would be hard to market as a food ingredient...
I suppose the point of this anecdote is to point out that chemicals, even those that we eat, can rear up and bite you when treated in new and creative
ways--and that the literature sometimes omits (for commercial purposes, I think, in the case above) details that might mitigate these risks.
It also makes me wonder if rigorously drying this stuff might have an effect? My guess is probably not, but you never know--and that is the point.
I'd consider writing up a hazard note for publication.
Heal up, and carry on,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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happyfooddance
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This is very interesting.
I have about half a kilo of sucralose that I bought from a japanese company a couple years ago. It is a fine crystalline solid, supposed to be
molecular and have no fillers. I haven't checked on the bulk of it but I can guarantee it isn't gassing HCl because nothing is damaged or corroded in
the container. I have a small jar in my spice cabinet which has 5-10 grams in it. Even just opening the container to remove the smallest amount I can
taste it strongly.
Once, years ago I extracted sucralose from Splenda (separated it from maltodextrin) using dry IPA. I didn't take notes, but I remember drying it with
liberal heat and didn't notice any HCl.
I am curious as well to these mechanisms and underlying processes.
In wg48's case, I wonder if his compound was dried first over a strong dessicant, if it would react the same? Either way, thanks for the urging of
caution with these inherently dangerous reagents.
Edit: spelling
[Edited on 2-12-2018 by happyfooddance]
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Ozone
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Try drying some of the sucralose in a desiccator over drierite for a month or so. In the normal atmosphere, the stuff isn't deliquescent, or anything,
but it does maintain an equilibrium with water adsorbed from the air which keeps it stable.
Via TGA, you can watch the water come off, and then away it goes. It also poofs up enough to blow the lid off the crucible...sub-optimal...
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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happyfooddance
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I have no idea what TGA is, my friend... I tried searching, but found nothing...
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wg48
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Dehydrating the dihydrate:
From: http://www.merckmillipore.com/GB/en/product/Dichloroisocyanu...
"Loss on Drying (105°C) 9.0 - 16.0 %" Probably to constant mass. The dihydrate is 14% H2O
Probagation testing:
From DOI: 10.1002/prs.680220202
Estimated decomposition enthalpy -1000cal/g
self-sustaining thermal decomposition reaction approximately .06 to 0.1 cm/s. Max temperature 600C
Onset of decomposition approximately 90C, with maximum rate at 150 to 200C
Decomposition products
From https://pubs.acs.org/doi/pdf/10.1021/ie502154b
"Starting from these results, we have characterized two decomposition reactions for SDIC, both giving two molecules of chlorine isocyanate (Cl-N=C=O)
and one molecule of sodium isocyanate (Na-N=C=O). However the first path corresponds to a two steps mechanism while the second is composed by a single
step. The first reaction, shown in Scheme 1, involves an initial breaking of two nitrogen - carbon bonds (G≠ = 44.1 kcal mol-1) to form a molecule
of chlorine isocyanate. The rest of the initial cycle decomposes with a low energetic barrier (G# = 12.6 kcal mol-1) to form another chlorine
isocyanate and a sodium isocyanate molecule. The second path involves a concerted breaking of N1-C2, N3-C4 and N5-C6 bonds of SDIC (see Figure 1) but
its energy is too high to be competitive (G = 48.0 kcal mol-1) with the first proposed reaction."
[Edited on 12-2-2018 by wg48]
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Ozone
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TGA = thermogravimetric analysis. https://en.wikipedia.org/wiki/Thermogravimetric_analysis
When coupled with differential scanning calorimetry (DSC) https://en.wikipedia.org/wiki/Differential_scanning_calorime... , you can get a lot of information about the thermodynamic behavior of the
material.
Aside the SDS for DCCA (for whatever they're worth) indicates that it decomposes at 240°C (no other info given), and that "Strong heating
(decomposition)...shock and friction are Conditions to avoid." They seem more concerned about environmental hazards.
Aside, the Wiley Guide to Chemical Incompatibilities indicates NCl3 (see attached).
Hope this helps,
O3
[Edited on 12-2-2018 by Ozone]
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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wg48
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I considered diy thermo analysis on a sample diluted with clean sand. I have multi temperature reader and pid controller that can interface to a pc,
but I need an appliction to display the results and manage the interface. Thats why I was so interested in Nemo's open source GC software but it has
no hardware interface only file input. Still hoping to get something like labview free.
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wg48
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But it said that was the reaction with water which makes no sense to me.
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Ozone
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We know it's tame in water. I'm thinking this was a typo (or some kind of brainfart) and they meant heating. The SDS cautions against heating the
stuff, Wiley mentions NCl3. My mind puts those two together (only because I know it doesn't kaboom when mixed with water up to 250 g/L @ STP).
The carbonyl diisocyanate (CDIC)-thing, however, is intriguing. It's been made from TCCA (Crazy Klapotke, again: https://pubs.acs.org/doi/abs/10.1021/acs.jpca.6b04245), so that's maybe not too much of a stretch. See also from DCCA and phosgene: https://www.google.com/patents/US3941873, where, "The reaction is accompanied by side-reactions and is difficult to control due to the
simultaneous formation of the highly explosive compound, NCl3."
Interestingly, CDIC will decompose to 3CO + N2, which could be frisky: http://www.chemistryviews.org/details/ezine/9824551/Stepwise... but this was photochemical. But, where would that phosgene be coming from, or what
else might do the trick?
Was the sample exposed to light just prior to the explosion, or was it illuminated the whole time?
In any case, here: http://datasheets.scbt.com/sc-236901.pdf it's indicated that, "Combustion products include: carbon monoxide (CO), carbon dioxide (CO2), hydrogen
chloride, phosgene, nitrogen oxides (NOx), other pyrolysis products typical of burning organic material." So maybe you get a little CDIC and NCl3.
Maybe you somehow got a lot?
An assay of the starting material would be helpful.
Aside, if you have a PID your experiment seems plausible--although it might not behave the same way on sand. DAQ or not, with the PID (assuming
calibration) you should know what temperature it's at when it goes. The tricky bit is that heating rate can have a significant effect on this
"characteristic" temperature. I've seen things go at much lower T when heated rapidly.
As I've said, once something blows up in my face I want to figure out why, so...
I'll keep thinking on it,
O3
Now that I re-read your original post, and knowing that decomposition can spread through the stuff from an initiating hot-spot, I'm wondering if it
was just a hell of a lot faster once a hot spot formed at the tube wall and spread into an already hot mass?
[Edited on 13-2-2018 by Ozone]
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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wg48
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O3: The idea of mixing sand with the NaDIC to reduce the possibility of thermal runaway by reducing the temperature rise for a given amount heat of
decomposition. It would also make it more difficult to detect the temperature rise.
.
The link I gave for the decomposition products said it was a theoretic decomposition because they could not find any definitive measured decomposition
products. So although they gave justifications for the reaction from bond energies, chemistry frequently is not that simple or it would be
impossible to electroplate chromium from an aqueous bath.
The propagation speed of the decomposition front given in the link was 1mm/s max but gave no temperature or conditions, was it in a tube or trough,
what atmosphere? I guess it was a trough in which case the propagation in a confining tube could be much higher and as you suggest if the all NaDIC
had been heated to near its decomposition temperature before decomposition started.
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Ozone
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Yep, I get what the sand was for--but, because you'd maybe be trying to recreate the incident (in a controlled way) in order to study it, the safer
option may not give the information you want (and, as you say, would confound measurement).
I hear you on the decomposition products. The way I'm seeing it, now (which is subject to change with new/better information), is that the stuff
decomposes around 240 °C (it's likely many changes happen before that). As this occurs, some phosgene is made that reacts with remaining DCCA to make
CDIC and NCl3 (both of which are quite bad). Perhaps if the stuff will propagate at 1mm/s (assuming rt), then it might do so much more quickly (making
more nasties, in less time, markedly increasing the concentrations, perhaps critically so).
It would be very interesting to test propagation rates through a trains of DCCA equilibrated to various temperatures, e.g. 25, 75, 125, 175, and 225
°C. I suppose they could be initiated with a glowing splint at one end (on a looong stick...or electronically), and the rates measured with a high
speed camera. No way I can set up to try that, though :/
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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AJKOER
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My understanding of the reaction trichloroisocyanuric acid (Cl-CNO)3 with water (and correspondingly, salts of this acid on hydrolysis, or with
acids):
(Cl-CNO)3 + 3 H2O --> 3 NH2Cl + 3 CO2 (g) (implied by one of the reaction scheme paths of R-CNO on page 9 at http://cdn.intechopen.com/pdfs/38589/InTech-Polyurethane_an_... )
NH2Cl + H2O = HOCl + NH3
HOCl + NH2Cl = H2O + NHCl2
HOCl + NHCl2 = H2O + NCl3
which clearly suggests the possible creation of some unstable and explosive NCl3.
[Edited on 23-2-2018 by AJKOER]
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Ozone
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Hmm. I'd have thought it was drier than that?
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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