Why would a 2/3 solution of vinegar to 1/3 water melt ice?

[Hector_St_Clare]

@Waterman

To clarify, this is known as the molal freezing point depression and it also helps that both the salt (sodium or calcium chloride used in winter on roads) or vinegar produce ionic solutions which, in effect, doubles the molal concentration.

Vinegar (which BTW is a 5-6% solution of acetic acid in water) is much handier to use on windshields.

Well, salt and vinegar are different. Salt entirely ionizes, or nearly so. Acetic acid is a weak acid, so only a little bit of it ionizes.