For pure water, the boiling point is 100 degrees Celsius (212
Fahrenheit) at one atmosphere of pressure, and the melting point is 0
degrees Celsius (32 degrees Fahrenheit) at one atmosphere of pressure.
At lower pressures (at high altitudes, for example, in Denver,
Colorado), the boiling point will be perhaps a couple of degrees lower.
For saltwater, the boiling point is raised, and the melting point
is lowered. By how much depends on how much salt there is. I'll assume
the salt is sodium chloride, NaCl (table salt). The melting point is
lowered by 1.85 degrees Celsius if 29.2 grams of salt are dissolved in
each Kg of water (called a "0.5 molal solution" of salt. The Na and Cl
dissociate right away when dissolved, and so for a 0.5 molal solution
of salt, there is a 1.0 molal concentration of ions). The boiling point
is raised by 0.5 degrees Celsius for water with 29.2 grams of salt
dissolved in each kg of water.
If your concentrations of salt are different, then you can scale
the boiling point elevation and melting point depression predictions
directly with the concentration.
These numbers come from the CRC Handbook of Chemistry and Physics.
(republished on 07/24/06)