> Oh.  Okay.
> It still boils at 212 degrees, basically, but takes less oomph to get
> there?
> --Maire "who me? I'm just a liberal arts kinda gal" NiNuanain
>
> "Decker, Terry D." wrote:
> >
> > Adding salt reduces the specific heat of water, which in turn reduces the
> > number of calories the water must absorb to bring it to a boil.  It doesn't
> > alter the boiling point, just the amount of heat needed to reach it.
> >
> > Bear

Sorry, Bear, that's not entirely correct. Adding any solute to water raises the
boiling point and lowers the freezing point, according to a mathematical
formula (which I can't recall) relating to the number of non-water particles in
solution.

Now, adding salt does lower the heat capacity of the water as well, but only in
LARGE amounts, and only if the volumes are equal. Why does salt water have a
lower heat capacity? If you look at 100 grams of pure water, it contains 100
grams of water, but 100 grams of 20 percent salt water only contains 80 grams
of water. The other 20 grams is the dissolved salt. The heat capacity of
dissolved salt is almost zero when compared to the high heat capacity of water.
This means that the heat capacity of a 20-percent salt solution is 80 percent
that of pure water. Twenty percent salt water will heat up almost 25 percent
faster than pure water and will win the speed race to the boiling point.

Please note that this will not hold true if you take two identical pots
containing one gallon of water each and add the salt to one pot because then
the volume of liquid in the salted pot will be greater than the one gallon
starting point.

Avraham

****************************************
Avraham haRofeh of Northpass (soon to be "of Sudentur")
     (mka Randy Goldberg MD)