Quote Originally Posted by eljefe281 View Post
Here's a fun question for chem geek...

What does 3500 ppm salt do to the freeze point of water?
Sorry I didn't notice this question to me before now, but the answer is, of course, disappointing. Remember that the freezing point depression for water is 1.86 ºC/m. 3500 mg/l / 58.44 g/mole / 1000 mg/g = 0.060 moles/liter which is essentially 0.060 moles/kg solvent (which is what "m" is...molality).

So 0.060 * 1.86 = 0.11 C = 0.20 F. Yes that's right, the salt in your pool only reduces the freezing point of water by 0.2 degrees Fahrenheit.

Richard