From: Glenn Garrett (gagarrett@nchfa.com)
Date: Mon Dec 23 2002 - 07:52:29 CST
actually, adding salt to water lowers the boiling point.
the pressure cooker idea won't work, because you cannot, unless you have a 'pressure cooker', make a tight enough seal, to maintain the pressure needed to raise the boiling point.
minor trivial observations recalled from high school physics.
>>> drbob@troop111.org 12/18/02 05:54PM >>>
Once the water has reached it boiling point, that's it. Boiling it
faster won't raise the temperature an iota - or do anything but waste fuel.
If for some (really strange) reason you really felt compelled to raise
the boiling point a little higher, there are two things you could do:
First, you could put a tight sealing cover on the pot and put a rock on
top of it. That increases the pressure inside (similar to a pressure
cooker - and higher pressure equals a higher boiling point). Of course,
THIS IS A REALLY BAD IDEA, since the rock will make the stove/pot
assembly really top-heavy, plus the lid is almost certaininly going to
blow off eventually, spraying boiling hot water everyone, probably
including on you. Second, you could add salt to the water, which raises
the boiling point through its colligative properties (remember them from
freshman chem?) Not recommended if you're trying to prep drinking
water, but I suppose it won't harm if you're heating water for dinner.
As has been pointed out by several responders, if you feel concerned,
the best option is to just let the water boil a little longer (and yes,
a soft boil is as good as a raging boil). Alternately, as I posted
several months ago, adding a small amount of Polar Pure to the water to
be boiled will alleviate any concerns as to how long to boil - iodine is
a mild oxidizing agent at stream water temperatures - but it's Mike
Tyson at the temperature of boiling water (again from freshman chem, the
rate of reaction doubles for every 10 degrees C rise in temperature).
My Crews do this with all stream water being boiled to prep dinners;
it's likely completely unnecessary, but it's a nice safety net.
- Dr. Bob
> -----------------------------
> My Thermodynamics is a bit rusty so I pose a question.
>
> Once water reaches its boiling point (for what ever temperature it is for
> the ambient pressure), can the liquid water go above that temperature (in
> a normal environment)? I know you can superheat steam, but can that be
> achieved with a stove and a beat up pot?
>
> I ask this because I've never agreed or understood why some people say to
> let it continue to boil past its boiling point temperature as if you can
> make the water hotter. I welcome someone to prove this to me as I have
> wondered about it for a long time.
>
> It would seem to me that if your boiling point for the pressure you are at
> (I say presure because that is more important than measuring your
> altitude) is 195F, in order to get your water above that temperature,
> would you not have to convert all your water to steam and then continue to
> heat the steam? I say this because I haven't seen many pots that hold
> their steam well :)
>
> So if this is correct, then why do some people recommend you continue to
> add heat to the system when the temperature can't really be increased any
> more. Or am I just wrong?
>
> Jason
>
> Retired Ranger
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