Aluminium arsenate is a inorganic compound with the formula AlAsO4.[1] It is most commonly found as an octahydrate. It is a colourless solid that is produced by the reaction between sodium arsenate and a soluble aluminium salt. Aluminium arsenate occurs naturally as the mineral mansfieldite.[2] Anhydrous form is known as an extremely rare, fumarolic mineral alarsite[3] A synthetic hydrate of aluminium arsenate is produced by hydrothermal method. with the formulation, Al2O3.3As2O5.10H2O.[4] Modification of aluminium orthoarsenate was carried out by heating different samples to different temperatures.Both amorphous and crystalline forms were obtained.[5] The solubility product was determined to be 10−18.06. for Aluminium arsenate of formula AlAsO4.3.5H2O[6] Like gallium arsenate and boron arsenate, it adopts the α-quartz-type structure.