Water and its effect on combustion.

[Chris Conlon]

At 01:35 PM 7/10/00 -0400, Bruce Plecan wrote:

>Anyone have a good current definition of inert, my teachings were the only
>inert things are Argon Zeon Neon, and a couple other gases.

I think the capsule definition is that nothing's inert at plasma
energies, or in the presence of the right radicals. The Noble
elements (helium, neon, argon etc) are pretty much the least reactive
elements, but even so people have been able to make helium compounds
(for instance) for many years now.

It might be more helpful to say "low energy" vs. "high energy". Water
as liquid is a fairly low energy compound. Sure it will break into
H and OH (or H and O) at high temperatures, but this takes energy,
just like pushing a rock uphill. You get the energy back (ideally)
in the end, when the rock rolls downhill, but the net was 0. (Now
none of this takes away from the fact of water being involved in
oxidizing CO to CO2. In that case the presence of water is speeding
up a reaction that otherwise would have occured by the side of the
road. The total energy is of course the same, the difference is
that more of it is released in the cylinder where it helps you.)

A fairly high energy compound like hydrogen peroxide (H2O2) is
very easy to break down into lower energy compounds, H2O and O2.
It's a rock that's already been pushed uphill. Free radicals are
at an even higher energy point. They're so reactive that they are
incredibly short lived (in most cases) and had not even been
detected for many years. It was only in the 60s (very roughly,
my history is poor) that chemists came to realize that a great many
chemical reactions actually involve radicals at the lowest level.

While we're on the subject of radical chemistry, it's interesting to
note (tho certainly no big secret) that a lot of anti-detonants work
by being radical traps, mostly for oxygen radicals of one sort or
another (O, OO, OH). Hydrogen radicals are the most important in the
normal ignition process, but the much more reactive oxygen radicals
are important factors in detonation, formation of NOx, etc. Excess
fuel tends to sop up oxygen radicals, and this is part of how it
reduces detonation.

   Chris C.

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