Why can salt remove ice?

The main reason of snowmelt salt snowmelt is its special physical and chemical properties, namely solubility, hygroscopicity and low freezing point.

Moisture absorption is reflected in the fact that the surface of snowmelt salt is usually surrounded by a film-like saturated salt solution. When the vapor pressure of this membrane solution is lower than the partial pressure of water vapor in the air, the snowmelt salt absorbs the moisture in the air and deliquesces. On the contrary, when it is higher than the partial pressure of water vapor in air, it is dry.

Extended data:

Snow melting salt is mainly divided into two categories. One is an organic snowmelt salt with potassium acetate as the main component. This kind of snow melting agent has good snow melting effect and low corrosiveness, but its price is too high. Generally used in airports and other places.

The other kind is chloride snow melting agent, including sodium chloride, calcium chloride, magnesium chloride, potassium chloride and so on. , commonly known as' deicing salt'.

Its advantage is cheap, but its disadvantage is serious corrosion to public infrastructure. In reality, according to different temperatures, the snowmelt salt is basically a mixture of sodium chloride and the corresponding chlorine salt (for example, calcium chloride tablets will absorb moisture and melt quickly when placed in the air, and will have obvious burning sensation when placed in hands), and some water and adhesive are added to make small particles of 3-5mm, which is convenient for spraying by machines.

Judging from the geographical location and local temperature in Nantong, the lost snowmelt salt mentioned in the news should be sodium chloride (the freezing point of sodium chloride dissolved in water is-10℃, magnesium chloride is around -20℃, calcium chloride is around -30℃, and acetic acid can reach -35℃), or it may be a mixture of common sodium chloride and calcium chloride in the market.

Baidu encyclopedia-snowmelt salt