USE OF A NITRATE SALT COMPOSITION AS A HEAT TRANSFER OR HEAT STORAGE MEDIUM FOR FIRST OPERATION OF AN APPARATUS CONTAINING THESE MEDIA

A heat transfer or storage medium containing a nitrate salt composition including at least one alkali metal nitrate and optionally alkaline earth metal nitrate; and, at least one alkali metal nitrite and optionally alkaline earth metal nitrite in an amount of 1.1 to 15.0 mol %. The molar amount of the alkali metal nitrite and optionally alkaline earth metal nitrite for a desired temperature is calculated byxnitrite=K6⁡(T)K6⁡(T)+PO⁢⁢2Xnitrite is the mole fraction of nitrite,K6(T) is the temperature-dependent equilibrium constant of the reaction nitrate ⇄nitrite+½ oxygen (NO3−⇄ NO2−+½ O2),pO2 is the oxygen partial pressure and T is the temperature of the nitrate salt composition.