Volume Nonadditivity of Liquid Mixtures: Modifications to Classical Demonstrations

Departures from Raoults law are often found in liquid mixtures resulting in volume nonadditivity. Modifications are proposed for experiments demonstrating volume contraction of water/ethanol and volume expansion of ethyl acetate/carbon disulfide liquid mixtures. A layer of paraffin oil or water is used to prevent mixing of the liquids at an earlier stage then desired. A demonstration of volume expansion in a CS₂/ethyl acetate system is proposed as well. The modifications significantly improve the ease of the demonstrations, which can be made even more impressive by coloring the liquids. A reaction vessel of simple construction is offered for a more vivid demonstration of the phenomenon.