Type X-zeolite in which 14.6, 31.00, 42.40, 57.80 and 59.00 Na+ ions have been exchanged with Cd2+ ions at 60oC. The decrease in % Cd2+ ion exchanged with increase in concentration of cadmium chloride solution is attributed to ‘salt imbibent’ and ‘concentration valency effect’. Thermogravimetric analysis (TGA) has been used to ascertain the zeolitic water content of all samples investigated. The thermal stability of NaX and CdX-zeolites samples were studied by using differential thermal analysis (DTA) curves as a function of calcinations temperature up to 1000oC and degree of Cd+ exchanged in type X-zeolite. The number of water molecules increases with increasing the Cd2+ ions per unit cell (p.u.c) in the zeolite. The DTA curves indicated that dehydrated NaX retained its crystal stability from 400 oC to 560oC and then re-crystallized to another form from 580 to 840 oC, while CdX-zeolite samples from 400 oC to 840 oC and then re-crystallized from 860 to 900 oC. The structures of NaX at above 880V and of CdX at above 960 oC collapse to an amorphous residue.