In an evaporating millimeter-sized drop, the flow field can be visualized by particles using conventional flow field measurement methods. However, to measure small-scale features in a relatively large system – such as the chemical distribution of molecules in a millimeter-sized droplet – while maintaining the global perspective needed to understand physical phenomena, is difficult but often important. Here, using physicochemical effects, we directly visualize the selective evaporation of a binary mixture droplet where the chemical distribution of a volatile component is not constant in time and space. We find that a mixture consisting of an organic solvent and deionized water dissolves suspended fluorescent polystyrene particles at a critical concentration, i.e. 90 wt. % of the organic solvent in water. Using this idea, we show that during evaporation the particles begin to disappear from near the contact line of a binary mixture droplet. Also, we develop a diffusion-dominated model to predict the experimental observations. For the low concentration of water in the mixture, the model shows good agreement with experimental measurements. We expect that the experimental idea introduced and demonstrated here will enable visualization of hidden features that have not been explored before.