In summary, we studied a set of five commercial PbI2 precursor sources often used to fabricate halide perovskite devices. Cumulative information gathered from three analytical chemistry techniques elucidate relationships between synthesis, I:Pb stoichiometry, impurities, properties, and performance. We substantiated our conclusions by performing purifications via aqueous recrystallization and evaluated its effectiveness. Our semiquantitative analysis provides significant insight into specific impurities such as acetate and K that influence the functional performance of the resulting halide perovskite material. Identifying the remaining impurities, and optimizing purification methods, will help to clarify subtle yet impactful compositional variations that influence lab-to-lab or process-specific differences, and contribute to perovskites reaching their full potential. Like all semiconductor materials preceding it, the halide perovskite technology will undoubtedly benefit from rigorous scrutiny of precursor composition and purification methods.