Alcohol (ethanol) has a freezing point of -114 degrees Celcius. Can this be used to determine the alcohol percentage in a drink? Last week i put a glass of whiskey mixed with some water (about 1:1) and the surface was just frozen after i left it a night in the freezer, which was somewhere between -22 and -17 degrees Celcius (i didn't take an accurate reading because i just wanted it to be really cold). So, given that whiskey has about 40% alcohol, the total theoretical percentage is about 20%, which means the freezing point of this "cocktail" is (0.2 * -114 + 0.8 * 0) = -23 degrees Celcius. Although not very practical because you're bound to a certain temperature range and it's hard to decrease the temperatur step-by-step, is this reasoning correct? The small experiment indicates so.. By the way, I've placed this one in the physics and not chemistry forum because it only deals with freezing points and volume ratios. Admin, feel free to move it if necessary.