An important question is whether it is possible to build a sensor to identify the constituents and estimate their volume fractions in a mixture. In this paper, frequency dependent permittivity measured from dielectric sensors was used to identify both chemical species and their volume fractions of binary mixtures. Our analysis using the data presented in the literature and on-chip coplanar waveguide measurements, in 1-30 GHz range, illustrates that complex permittivity measurements are sufficient to estimate the volume fractions when the constituents of the mixture are known. Changes in concentrations are required to identify the constituent chemicals of binary mixtures when the constituents are unknown. Additional information, such as nonlinear dielectric properties, is required to identify constituents and volume fractions in mixtures with many chemical species.