UBC Okanagan associate professor of chemistry Stephen McNeil explains the chemistry behind ice and snow removal.
“Pure water freezes at zero degrees Celsius, but by adding salt, the freezing point is decreased. Consequently, it is used to de-ice roads and equipment, such as aircraft,” says McNeil.
Although rock salt (sodium chloride) is the most recognized compound to add, another salt, magnesium chloride, may be more effective. Because magnesium chloride dissolves into three particles, rather than two like sodium chloride, the freezing temperature is lowered even further, and less magnesium chloride needs to be used.
As a result, each salt has an optimal temperature of use. Sodium chloride works at temperatures from zero to minus six degrees Celsius and magnesium chloride works down to minus twelve degrees.
Although, if used too liberally, both salts can cause corrosion. They are also both natural substances and are not toxic.
Depending on which salt is used, the streets may take on a different colour. Rock salt application may result in a pink hue.