As the complex multicomponent organic phases that we previously studied 63,64 also feature 3D Ising exponents, interpreting structure in organic phases using the theory of critical phenomena is likely generalizable and approachable with simplified model systems. The systems we study here contain no aqueous solutes, such as metals or coextracted acid or water, demonstrating critical fluctuations are fundamental to the extractant/diluent mixture and the same scaling laws can describe structure in both simple and complex organic phases. We find well-known relationships between phase behavior and extractant and diluent molecular structure are the same as for metal-and acid-containing LLE sytems: increasing extractant chain length or decreasing diluent chain length suppresses third phase formation and therefore the critical fluctuations. This suggests that high-throughput screening of compatible extractant/diluent pairs that suppress third phase formation might, to first order, be achievable by considering simplified binary mixtures. This could dramatically simplify experimental testing and computational modeling.