Celsius is measured in Freezing and boiling points of fresh water, but Fahrenheit degrees are measured by the boiling and freezing points of salt water. Salt Water freezes at 0 degrees F and boils at 100 degrees F.
In simplicity, salt decreases the freezing temperature of water by allowing the particles of water (H2O) to more faster at lower temperatures. By giving this answer, I assumed you are familiar with...
I conducted an experiment for one of my classes on this one: I had 6 oz. of cold water and added teaspoons of salt until no more could dissolve (until the solution became saturated). I then repeated...
Adding salt to water raises the freezing (and melting) point of water (to below 0 °C or 32 °F). Salty water will freeze at a lower temperature than pure water, thus making it take longer to freeze...