Rare Event Mystery of Exploding Massive Municipal Water Tanks

[imatfaal]

!

Moderator Note

 

Humblemunn - stop using other threads to advertise your speculative theory. That behaviour is considered hijacking and future instances may just be hidden - please do not continue.

 

[John Cuthber]

OK, lets assume there is not ever a high concentration of any compounds to form a gaseous eruption. Also, your proposal of the action of Zn and water to form H2 is not likely given the water temperature. However, I believe your idea is close.

 

I was recently exploring (seemingly unrelated to this topic) a hypochlorite based Aluminum and Copper battery. Here is the chemistry per my research. To quote (see http://www.exo.net/~pauld/saltwater/ and http://sci-toys.com/scitoys/scitoys/echem/batteries/batteries.html ):

 

"In the bleach battery, sodium hypochorite (NaOCl), the major constituent in bleach, and hypochorous acid (HOCl), a minor constituent, are reduced, according to equations 6 and 7:

(6) ClO- + H2O + 2 e- --> Cl- + 2 OH- Eo = 0.89V

(7) HOCl + H+ + e --> 1/2 Cl2(g) + H2O Eo = 1.3V

 

The possible reactions involving aluminum are given by equations 8 and 9:

(8) 3 ClO- + 2 Al + 2 OH- + 3 H2O --> 2 Al(OH)4- + 3 Cl- Eo net = 3.21 V

(9) 3 HOCl + Al --> Al(OH)3 (s) + 3/2 Cl2 (g) Eo net = 3.93 V "

 

The author also notes that "Even though there is relatively little HOCl in bleach, the latter reaction is more favored because of its large potential of 3.93 volts. Over time, you will see both green cupric hydroxide (Cu(OH)2) and black cupric oxide (CuO). Black CuO is formed from green Cu(OH)2 by the loss of water, which happens over time."

 

The implied reactions at anode:

Al + 3OH- ⇒ Al(OH)3 + 3e-

 

given reaction at cathode (copper);

3 HOCl + 3 H3O+ + 3 e- --> 3/2 Cl2(g) + 3 H2O

 

for an implied net of:

3 HOCl + Al --> Al(OH)3 (s) + 3/2 Cl2 (g) Eo net = 3.93 V "

 

More, fully, I would express the reactions with respect to HOCl powered cell as follows:

H2O <--> H3O+ + OH-

 

with the implied reactions at the anode:

Al + 3OH- ⇒ Al(OH)3 + 3e-

 

and the reaction at cathode (copper);

3 HOCl + 3 H3O+ + 3 e- --> 3/2 Cl2(g) + 3 H2O

 

for an implied net reaction of:

3 HOCl + Al --> Al(OH)3 (s) + 3/2 Cl2 (g) where Eo net = 3.93 V

 

A very important comment by the author above is "Even though there is relatively little HOCl in bleach", implying that the above reactions proceed even at low concentrations.

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So, how does this apply potentially to water tank problems (ruptures, explosions, etc.)?

 

Consider an Aluminum alloy tank with at least one copper pipe in contact with an ionic (mineral rich) water containing hypochlorite or HOCl (from the reaction of H2CO3 on NaOCl added during purification, for example).

 

Bottom line, with time the Aluminum tank will corrode (forming Al(OH)3 more precisely) causing it to weaken. In addition, the protective Al2O3 will be removed allowing the side reaction:

2 Al + 3 H2O --> Al(OH)3 + 3 H2 (g)

 

to proceed. As such, an explosive combination of H2, O2 and Cl2 may potentially form over time in the tank. The actual air concentration of Cl2, given its solubility, may vary with water temperature and the presence of dissolved CO2.

 

Note, this explanation requires no high concentration of any compound, just a persistent use of chlorination in an Aluminum tank with continuous (or periodic with change in water levels) exposure to copper fittings. Also, in the case of a Zinc plated tank, similar chemistry follows.

 

I have performed the above reaction as follows:

 

Combined bleach (NaOCl) and vinegar (which contains Acetic acid HAc) in the volume ratio 1.4 parts of 5% vinegar to one part of 8.25% extra strength chlorine bleach. Then, add a piece of copper metal which will function as the cathode and an Aluminum source to act as the anode (finely cut up Al foil, for example, will do). Finally, add a touch of sea salt (better than NaCl) to act as the electrolyte to get things started. An interesting aspect of the reaction, performed in a closed vessel with shaking, is how long its takes to completely dissolve the Aluminum (a couple of hours) and a warming of the reaction mixture. No heating is required.

 

As expected, using an excess of Aluminum slowly over a course of days, does form hydrogen gas. I tested it by exposing it to a flame and did observe a loud retort (caution: it is know that H2 and Cl2, and/or O2, can produce a kinetically powerful explosion).

It seems to have escaped your notice that people don't drink bleach.

"As expected, using an excess of Aluminum slowly over a course of days, does form hydrogen gas. "

Congratulations. You seem finally to have understood what I said in the 5th post in this thread in early June.

Reactive metals (I used zinc as an example, but aluminium is even better) will produce hydrogen by reaction with water.

[ajkoer]

John:

 

Note my quote from the author: "Even though there is relatively little HOCl in bleach" the reaction with HOCl apparently proceeds nevertheless because of its greater electrial potential. Now, so called 'free-chlorine' (defined as Hypochlorous acid and hypochlorite ion) is in all of our drinking water unless you water is made safe via ozone or chloramine.

 

Interestingly, employing higher chlorination levels is one way of addressing issues with declining water purity, so my suggested reaction path may be observed even more frequently in Aluminum alloy tanks with exposure to copper. It also makes the water a better electrolye for such electrochemical reactions.

 

Unfortunately, if my hypothesiis is correct, it is supportive for the use of NH2Cl in place of Cl2 or NaOCl or ClO2. However, it also argues for ozone if there are a large number of these Aluminum alloy water tanks.

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Fortunately for those fans of my prior speculations into the possible contributory nature of nitrates in our water to the problem of erupting/exploding water tanks, there is ,good news. Here is some of the chemical reactions associated with Aluminum (and Al tanks) after the protective Al2O3 has been penetrated (see http://en.wikibooks.org/wiki/Inorganic_Chemistry/Qualitative_Analysis/Tests_for_anions ) to quote:

 

"1. 3NO3- + 2Al + 3H2O → 3NO-2 + 2Al(OH)3

2. NO-2 + 2Al + 3H2O → NH3 + 2Al(OH)3 + OH-

3. 2NO-2 + 2Al + 4H2O → N2 + 2Al(OH)3 +2OH-

Nitrate reduction was found to be pH dependant. At pH values less than eight
no nitrate reduction took place. Above pH 10.5 nitrate was reduced upon addition of
the aluminium powder. Aluminium powder has been suggested for the denitrification
of sodium-based nuclear wastes, employing the nitrate to ammonia and ceramic
(NAC) process (Mattus et al., 1993, 1994)."

Here are encouraging comments from another source (see http://en.wikibooks.org/wiki/Inorganic_Chemistry/Qualitative_Analysis/Tests_for_anions ):

"The Nitrate ion can easily be reduced to ammonia with either Devardas Alloy or Aluminium Foil. The aluminium is a very powerful reducing agent, and this combined with heating causes the nitrate ions to form ammonia gas. This can be tested for by holding a piece of damp red litmus paper over the end of the test tube. The ammonia will form alkaline ammonium ions in the water and turn the paper blue.

4NO3-(aq) + 6H20(l) -> 4NH3(g) + 9O2(g)

Aluminium powder is not shown as it merely catalyses the reaction."

 

In my opinion, the author's last quoted reaction above must be more clearly presented and interpreted in an electrochemical setting. Interestingly, Devarda's alloy is an alloy of aluminium (44% – 46%), copper (49% – 51%) and zinc. Also, again the Aluminum, acting as the anode, is corroded to Al(OH)3 in an electrochemical reaction.

Edited August 30, 2013 by ajkoer

[John Cuthber]

FFS!

"Note my quote from the author: "Even though there is relatively little HOCl in bleach" "

relatively little i.e. a few percent.

So, something like a thousand or ten thousand times higher than the free chlorine levels in drinking water.

Seriously, do you really not understand that difference?

Didn't you realise that you were talking nonsense?

And please don't clutter up the site with utter garbage like this

"4NO3-(aq) + 6H20(l) -> 4NH3(g) + 9O2(g)"

 

or "Aluminium powder is not shown as it merely catalyses the reaction."

even if you found it somewhere on the web.

It's total nonsense.

 

Of course, the very low levels of nitrate would stop it making a difference even if it wasn't rubbish.

[ajkoer]

John:

 

I agree on your comment on the reaction cited and have edited my comments to be more clear that the author is, in my opinion, referring to an electrochemical reaction using non-standard notation for that field, which certainly can be confusing and viewed, to quote you, as "utter garbage".

 

But, your comment on the important of concentration is similarly misplaced, to the best of my understanding, in an electrochemical setting. That is why an insignificant amount of HOCl, found normally in Bleach, is still significant.

 

The other less obvious point is that a low concentration, but still significant reaction, over time can be, in the long term, damaging/corrosive to an anode.

 

Another point I should make is that in the references on these electrochemical reactions I have provided above, there is a large number of possible side reactions in addition to the major electrochemical reaction. My nitrate reduction example is, in my opinion, but one possible minor reaction scenario with potentially disastrous consequences.

 

Finally, the degrading of my analysis on this mystery to the category of speculation is NOT appropriate in a legal sense, in my opinion. My opening comments alluded to an authoritative report (a government commissioned investigation) on one of the exploding water tank occurrences. The first page of that report clearly alludes to the re-finishing of the water tank with a zinc coating as potential causative factor. While it has taken me some time, the commission's comments to me now suggest, more likely than not, an electrochemical based explanation. As such, my latest path is clearly within this legally endorsed scenario with suggested (and documented) electrochemical paths.

 

More interesting in another field, and pure speculation by a non-lawyer myself, but could a derogatory comment to another espousing a legally endorsed position (by a respected government authority no less) be considered libelous? My argument being there may be an existing basis for legal validity with respect to a general framework (electrochemical), which therefore could provide a frame for establishing the untruth of a contradictory statement which dismisses, in its entirety, said viewpoint. Add a pinch of ridicule and we are off to the courts, ... just joking, but I would like a real lawyer's comment anyway, as I find this stuff fascinating, and useful on how to behave on forums and the like in the internet age.

Edited August 30, 2013 by ajkoer

[John Cuthber]

So, you think that a factor of ten thousand in the concentration doesn't matter?

It's not a matter of notation- the fact is that, at best, it's not relevant to the circumstances you are describing.

 

"But, your comment on the important of concentration is similarly misplaced, to the best of my understanding, in an electrochemical setting. That is why an insignificant amount of HOCl, found normally in Bleach, is still significant."

There's (relatively speaking) plenty of HOCl in bleach.

But there's practically none in drinking water.

That's the problem here. You keep trying to claim that some obscure reaction is responsible, without checking if the reaction is actually plausible.

HOCl that's not present can't explode anything.

 

"The other less obvious point is that a low concentration, but still significant reaction, over time can be, in the long term, damaging/corrosive to an anode."

You don't (as I have pointed out several times , and at length) need some obscure reaction whether it's electrochemical or not..

Corrosion of metals like zinc and aluminium will account for hydrogen.

 

"Finally, the degrading of my analysis on this mystery to the category of speculation is NOT appropriate in a legal sense"

Oh yes it is.