Determination of the solubility limit of a strongly colored organometallic reagent in a mixed-solvent system provides an example of quantitative solubility measurement appropriate to understand polymer, nanoparticle, and other macromolecular aggregation processes. The specific example chosen involves a solution of tris(dibenzylideneacetone) dipalladium(0), Pd[subscript 2](dba)[subscript 3], in THF/H[subscript 2]O mixtures, which has the desired properties of high absorption in the visible range ([lambda][subscript max] = 528 nm) and significant difference in solubility in the two solvents THF and H[subscript 2]O. Pd[subscript 2](dba)[subscript 3] is readily available, safe, and commonly used in nanoparticle syntheses. The application of Flory-Huggins theory permits the fit of a quantitative model to data obtained from a straightforward laboratory experiment that can be conducted in less than 3 h. The absorbance of this compound is easily measured by UV-vis absorption spectroscopy. The application of the Beer-Lambert law to the data in this experiment is a useful exercise for students because the absorbances span three orders of magnitude. (Contains 3 figures.)