Any substance which is a solute that lowers the freezing point of a
solvent. Water(
Hydrogen oxide) is the usual solvent. The solute is usually
sodium chloride, calcium chloride, ethylene glycol(toxic), propylene glycol(non-toxic, safe), 1,2-Butyleneglycol(nontoxic) glycerol(nontoxic), ethanol, and a tick protein called IAFGP. Ticks have a protein called IAFGP that is triggered during winter months, which protects them from the cold. The freezing point of the solution gets lowered. Freezing point depression is a colligative property.
I put propylene glycol
antifreeze in my car and it resisted
freezing in the winter.
The dog accidentally drank some propylene glycol but turned out fine. If it would have been ethylene glycol,
the dog would have died.