Ammonium Alum crystallizes in regular octahedral form with thinning edges and is highly soluble in water. When heated near the melting point, it will produce pores then the porous mass is called "Burn Alum". The melting point is about 92° C. in water of crystallization. Neutral Alum is obtained by adding some sodium carbonate to the alum solution and immediately causes the separation of the alumina. Alum is found as a mordant and purification of wastewater