Melting Point of an Ethanol/Water Mixture

I’ve been storing spirits (40% ABV) in the freezer and they’ve always remained liquid at that temperature. Recently, in my naive understanding, I placed a bottle of vermouth (18% ABV) in there and was surprised to find the next day all I had was a bottle of hard slush. This got me thinking: at what proportion of alcohol will that solution not freeze at typical freezer temperatures?

In my dim memory of chemistry, I remember that a mixture of two miscible compounds will have a melting point (freezing point) lower than the melting point of each compound individually, with a sharp depression at the eutectic point. Is there anywhere to find an ethanol-water melting point curve?

I suppose for the purposes of this question, we might first consider a solution of pure ethanol and water without impurities, but we could also consider the effects of the various other compounds typically found in alcoholic beverages.

Ideal freezer temperature is variously quoted at 0˚F or -20˚C. This corresponds to roughly 32% - 33% alcohol. Here’s a rough table: http://www.engineeringtoolbox.com/ethanol-water-d_989.html

A quick search turns up this:

http://commons.wikimedia.org/wiki/File:Phase_diagram_ethanol_water_s_l_en.svg
18% ABV freezes well before 40% ABV, so it’s not surprising. You really need quite a bit of ethanol – about 93-94%, judging from that picture – to get the eutectic point. -20C corresponds to about 30% alcohol, as Nametag said

Aha! “Phase diagram”–the term I couldn’t think of. Thanks, Cal!