The differential scanning calorimetry (DSC) in NaxRb1-xNO3 pseudo-binary systemare presented by varying x from0 to 1. The formation of an intermediate compound and its effect on the phase transitions of RbNO3 is explained in terms of redistribution of energies involved in various transitions. Corresponding phase diagramis constructed. DSC peak at about 173 C with eutectic composition 0.46 (Na mole fraction) has been attributed to the formation of a congruently melting compound NaRb(NO3)2. X-Ray Diffracto grams (XRD) indicate the formation of this newcompound. DSCpeak corresponding to the melting of this compound and XRD lines related to this compound are found to grow with x until it reaches the eutectic composition.