Generally water soluble salts tend to 'fit between' the molecules of water such that the volume of the resulting solution does not increase much relative to the volume and added mass of the salt. So the result is that the solution generally has a higher density than pure water.
But are there any special cases; any salts or compounds that result in an expansion of the resulting solution volume such that its density actually decreases?
Sodium polyacrylate comes to mind, but if I'm not mistaken, the expansion doesn't take place until a significant amount of the compound is added, and then only after the liquid is changed to rather a gel or solid. My question relates to the resulting solution actually being a liquid with density < 1.0 g/cm³.
So then if not for water, are there solutions of other solvents that might behave this way?