The four-week student project described in this article is an extension of protein thermal denaturation experiments to include effects of added cosolutes ethylene glycol, glycine betaine, and urea on the unfolding of lysozyme. The transition temperatures and van't Hoff enthalpies for unfolding are evaluated for six concentrations of each cosolute, and the results are used to calculate cosolute preferential interaction coefficients with folded and unfolded lysozyme. Preferential interaction coefficients are used to explain lysozyme stability in cosolute solutions. (Contains 2 notes, 2 figures and 1 table.)