Studies on third phase formation during the extraction of uranyl nitrate from nitric acid media by N,N-dihexyl derivatives of n-hexanamide (DHHA) and n-octanamide (DHOA) in n-dodecane have been carried out. Limiting organic concentration (LOC) of uranium(VI), above which the third phase formation takes place, has been evaluated as a function of nitric acid concentration, extractant concentration, temperature and the ionic strength of the aqueous phase. Limiting organic concentration (LOC) of HNO3, above which the third phase formation occurs has been evaluated as a function of nitric acid concentration as well as extractant concentration. The influence of phase modifiers on LOC is also examined. Results indicate that the LOC value obtained for DHOA is significantly higher as compared to that for DHHA. Uranium analysis of third phase formed has been carried out. Viscosity data on U(VI) - DHOA -n dodecane system has also been obtained.