Ask A Scientist Chemistry Archive

name         Jonathan
status       other
age          40s

Question -   Hi interesting site. I am a captain of the New York Fire
Department. Working in Chinatown section. I recently had a fire in a
restaurant basement I believe was started by an aluminum reaction with a
chemical from trick type matches. (Snake matches from Summit Match
Company, which is closed.) I would like to know the chemical which made
the aluminum hot enough to ignite a fire. (A water leak soaked these
matches and the solution wet aluminum foil rolls) when I applied this
solution to the aluminum foil it became very hot. Please email me if you
can when you read this. I really appreciate your time and maybe your
input could help me out in resolving this matter.
--------------------
Jonathan,

First, my heartfelt thanks and condolences to you and your fellows for your
services and the losses you sustained in the tragedy of 9-11.

I do not know the specific composition of the matches to which you refer.
Nevertheless, aluminum will react violently with alkalis such as sodium or
potassium hydroxide. It is the reaction that occurs when crystal Drano is
contacted by water. Drano is aluminum chips and lye. So long as it is dry, no
reaction. When wet, a reaction proceeds that is very exothermic (hot) -- in
addition, hydrogen gas is liberated.

I do not know if this is of assistance, but perhaps it might be a lead to
other information.

Regards,
ProfHoff 443
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         Hazard analysis: Circumstances/clues described:
( aluminum + ??? -----> combustion/explosion ),  possible involvement of
water, spontaneous combustion,  pyrotechnic materials ( any Al powder vs. 
Al foil
would be especially hazardous), ignition source available (matches).

     Potential scenarios:
         1. Thermite reaction. A famous, favorite, dangerous chemical
demonstration:
2Al(solid) + Fe2O3(solid) ----> 2 Fe + Al2O3 (heat of reaction about -848 kJ
for reaction as written). A mixture of the powdered reactants could be set
off by any source of ignition, e.g. the matches. This is a nasty reaction,
known to burn holes in lecture demonstration benches.
         2. Since pyrotechnics may be involved ANY reactions involving a
strong oxidant plus aluminum are possible. One reaction used for
demonstration rockets is:
6 NH4ClO4 (oxidant) + 10 Al = 5 Al2O3 + 6 HCl + 3N2 + 9 H2O
This would also be set off by any source of ignition (matches).
         3. Aluminum metal (especially powdered) can react with water in the
presence of base or acid to produce hydrogen gas. Any modest amount of heat
or other energy source -- a match, a static spark, light, a cosmic ray!, and
so on will ignite the hydrogen which in turn will ignite any nearby
combustibles. The reactions are:
2 Al + 2 (OH -1) + H2O ----> Al2O3 + 2 H2
Al( metal) + 6 H( +1)  ----> 2Al( +3) + 3H2
         In these reactions it does not make much difference what the counter
ion is because these are general oxidation reactions of metals producing
hydrogen gas.
Aluminum foil will dissolve in either strong base or acid quite readily, and
in a confined space could get very hot, very quickly and set of the
combustion of hydrogen.
         It is also worth noting that these latter reactions may not be able
to be extinguished with EITHER water or CO2. The addition of water just
provides more "fuel" to the fire -- generating more heat than the cooling
effects of water. I am not sure about Al, but I have witnessed an attempt to
extinguish a sodium fire with a CO2 extinguisher, that caused the fire to
flare UP almost exploding. The reaction:
          2 Na(metal) + CO2  ----> Na2O + C0(gas)
Of course, the reaction did not stop there. The Na2O reacted with
ever-present water vapor to produce H2, which in turn reacted with the
oxygen, and the CO gas also served as a fuel. Some carbon particles were
also observed, probably due to the further reduction of CO2 to C(elemental).
It was quite spectacular!! Had to go to "plan B" and dumped a bucket of sand
on the mess. Fortunately, the reaction was confined to a fire-proof fume
hood.

For some further information you might contact the International
Pyrotechnical Institute at: http://www.ipsusa.org  and the web page:
www.ipsusa.org/ips29html
Hope this helps.

Vince Calder
==============================================================
I am not familiar with these matches, so I do not know exactly what they used.
Regular matches use phosphorus to ignite and sulfur and an oxidizing agent
to actually burn.  Aluminum is actually a very reactive and flammable metal,
but it is normally protected by an inert coating of aluminum oxide.
Dissolving the oxide, though, exposes a fresh aluminum surface, which reacts
vigorously with air and water.  Sulfuric and nitric acids can dissolve
aluminum oxide, as can alkalis such as lye or caustic potash.  My guess is
that one of these alkalis is present in your Snake Matches.  Mixed with
water, the alkali makes a caustic solution that dissolves the aluminum's
oxide coating, allowing the aluminum to react with water and generate heat.

The same reaction occurs in the commercial drain cleaner "Drano."  This
consists of sodium hydroxide, blue dye, and aluminum turnings.  When placed
in water, the lye removes the oxide coating from the aluminum pieces,
causing them to fizz as they displace hydrogen from water.  This makes it
sound like the Drano is really working effectively, even though it's the lye
that actually cleans out the drain clog.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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