What temperature does salty water freeze at?
When you add salt to water, you introduce dissolved foreign particles into the water. The freezing point of water becomes lower as more particles are added until the point where the salt stops dissolving. For a solution of table salt (sodium chloride, NaCl) in water, this temperature is -21°C (-6°F) under controlled lab conditions. In the real world, on a real sidewalk, sodium chloride can melt ice only down to about -9°C (15°F).
