# Why is the boiling point of rectified spirit lower than alcohol absolute?

The boiling point of rectified spirit is ($78.1~\mathrm{^\circ C}$) while that of absolute alcohol is ($78.3~\mathrm{^\circ C}$). I know its too small, but shouldn't the addition of impurities increase the boiling point?

What qualifies as an impurity? Is it that solids like salt only can be called an impurity? — which increase the boiling point of water?

• I'd be surprised you could even measure the difference between those boiling points in normal conditions. Is the difference really significant? May 28 '16 at 11:54