This section is from the book "A Treatise On Beverages or The Complete Practical Bottler", by Charles Herman Sulz. Also available from Amazon: A Treatise On Beverages.
When alcohol is mixed with water an elevation of the temperature is observed, and the mixture assumes for a short time an opalescent appearance from the dissolved air, which is expelled in numerous minute bubbles, after which it becomes perfectly transparent; when it has cooled to the ordinary temperature the volume will be found diminished. This contraction is- greatest on mixing 55 measures of absolute alcohol with 45 measures of water, which will yield 06.23 measures of weaker alcohol, showing a loss of volume equal to 3.77 per cent. - N.D.