4,4'-Bipyridine Chemical Properties Melting point 109-112 °C(lit.) Boiling point 305 °C(lit.) density 1.2814 (rough estimate) refractive index 1.6057 (estimate) Fp 304-305°C storage temp. Store below +30°C. solubility 4.5g/l form Powder pka pK1:3.17(+2);pK2:4.82(+1) (25°C) color Off-white to beige