It is shown on the example of the analysis of bulk properties of an aqueous tert-butanol solution that the structure of solution can be better understood using the volumes of their different components. Within molecular dynamics models of solutions, their individual components and volumes can be determined using the Voronoi partition. This is an additional information with respect to the traditional approach where bulk characteristics are calculated from the total solution density. The Voronoi molar volumes of components, components of excess molar volume of the solution, and the apparent alcohol volume are calculated. The nature of the minimum on the apparent volume curve and the association of tert-butanol molecules in water at low concentrations is discussed.