Deuterium oxide (D2O, heavy water) is deuterated water containing 0.05wt.% 3-(trimethylsilyl)propionic-2,2,3,3-d4 acid, sodium salt. It is safe and inexpensive source of deuterium (D) for the D/H exchange reactions. The equilibrium constant for the exchange of deuterium between hydrogen (H) and D2O molecules has been determined. Reports suggest that gelatin gels prepared in D2O show higher rigidity than gels prepared in water. The influence of temperature on the heat capacity of deuterium in crystalline and liquid state was studied calorimetrically and its melting point, enthalpy and entropy of fusion were determined. Its utility as a potential therapeutic agent in treating human pancreatic cancer has been studied.