Lower Freezing Point to -10￿F?

How much salt do I need to add to 40 gallons of water to lower the freezing point to -10F?
- Baz (age 10)
San Antonio, TX, USA

You can't do it. There's only a certain amount of salt (NaCl) that will stay dissolved in the water, giving what's called a saturated solution. The freezing point of saturated saltwater solution is about -21°C, or -6°F. Maybe some other salt would work, but not ordinary table salt.

Mike W.

(published on 02/04/2012)

Correction: How much salt do I need to add to 40 gallons of water to make a saturated solution?
- Baz (age 10)
San Antonio tx usa

It's about 360 gm salt/liter of water.


40 gal is 160 quarts or about 150 liters, so that would be about 54 kg of salt. That's almost 120 pounds.

Mike W.

(published on 02/05/2012)