Assay (iodometric, onanhydrous substance as SO2))45.0-55.0%Clarity and color of solutionclear & colorlessAlkalinity passes testpH of 2% solution 9.5-10.5%Sodium sulphite(Na2SO3) max 5.0%Iron (Fe) max 0.001%Sulphide passes tesLoss on drying (105oC) max 27.0%