The sodium in synthetic faujasite, commercial zeolite-X, was exchanged with copper cations at room temperature. A maximum number of 70 out of 86 Na cations were replaced with 35 copper cations (1). The copper exchanged zeolite was divided in six equal parts. Five of them were calcined at 43, 73, 112, 150 and 195 deg C. After calcination the samples were eluted with saturated solution of ammonium chloride to remove copper cations from open sites (super-cages) of the zeolite (Fig 1). The remaining copper cations were in locked sites (sodalite-cages or hexagonal-prisms). Using XAS edge-jump as a measure of quantitative analysis, we found that 9.0, 11.5, 12.7, 13.3 and 20.0 copper cations were locked at calcination temperatures of 43, 73, 112, 150 and 195 deg C respectively. The analysis of the first shell Fourier Transformed radial distribution shows that cations at site I in the hexagonal-prism and site I ‘ and II ’ in the sodalite-cages, adjacent to site I, are distributed at equal proportion, independent of temperature.