Partial specific volumes of lipid and water in mixtures of egg lecithin and water.

We describe in this paper measurements of the partial specific volumes of lipid (upsilon L) and water (upsilon W) in mechanical mixtures of egg yolk lecithin and water over a range of hydrations (5-55 wt% water) that includes the region at which excess water appears. upsilon L and upsilon W are found to be very nearly 1 cm3/g over the entire range. The water activities of the mixtures were also determined and found to be the same as for lipid deposited as oriented multilayers on solid substrates.