vincent p. norris wrote:



Thanks, Jim, but what I meant by "function" is, what does the
phosphate (or nitrate) DO?

Isn't ammonium nitrate the stuff used to make car bombs? If so, why
would it be dropped onto a fire?

"Ammonium" is loaded with hydrogen and "-ate" means lots of oxygen.
Neither would seem to ideal for quenching a fire.

vince norris


Ammonium nitrate, by itself, is not a hazard. Growing up on a farm, I
regularly hauled
8-ton loads of the stuff without any problems.

Ammonium nitrate, when mixed with a fuel such as a hydrocarbon, is a
great oxidizer. The
combination is what makes the truck bombs (I don't know if they use it
for car bombs)
go boom. You also don't need terrorists to set it off - do a search of
the Texas City disaster
(or the Grand Camp - the ship that set it off) to see an industrial example.

As for why it's used in arial drop flame retardants, I don't know if
there's any fire related
reasons. Maybe it helps modify the water's viscosity or something.
However, I suspect
that the fact that it's a good fertilizer is at least part of the
equation. You don't want
something that's toxic (save the trees from fire only to kill them
slower with a poison),
and this will help (a) the fire damaged trees in their recovery process,
and (b) the re-vegetation
process.

Rich Lemert