Precipitation of magnesium aluminate hydrate with faster addition of ammonia at desired pH causes agglomeration. Agglomerated powder, without any further treatment, on calcination forms intermediate compounds at low temperatures (= 900°C). The intermediate compounds on further heat treatment (= 1000°C) decompose into MgO, MgAl2O4 and a-Al 2O3. Effect of agglomeration and absorption of foreign ions such as Cl-, SO42-, and NH+4 in complex compounds probably cause loss of Al3+ and Mg2+ ions during heat treatment, and stoichiometry changes. Powders prepared by continuous method with better control of process parameters than batch process yields better spinellization. © Indian Academy of Sciences.