A , = H = n = R = s = t = T = x, = d = r, = r;' = z = I T =fitting parameter in excess properties equation enthalpy of forming new surface, ergs per sq. cm. fitting parameter in excess properties equation gas constant entropy of forming new surface, ergs per deg. per sq. cm. temperature, O C. temperature, O K. mole fraction of component i density, g. per cc. individual Gibbs surface excess of component i, moles per composite Gibbs surface excess, moles per sq. cm. summation sign surface tension, dynes per cm. or free energy of forming sq. cm. new surface, ergs per sq. cm. LITERATURE CITED (1) (2)Physical properties were determined on purified samples of 38 organic sulfur compounds and 18 organic nitrogen compounds. Most of the compounds were donated by interested laboratories for augmenting the spectral data on these types of compounds. Special handling techniques to prevent contamination or decomposition were employed during purification, storage, and property measurement. Boiling point, freezing point, density at 20' C., and refractive index (sodium D and mercury g lines) at 20' C.were determined. Derived functions calculated are refractivity intercept, specific dispersion, and molecular refraction.