d. Sample analysis: Stir sample with a magnetic stirrer and pipet a measured volume onto a glass-fiber filter with applied vacuum. Wash with three successive 10 ml volumes of reagent-grade water,allowing complete drainage between washings, and continue suction for about 3 min after filtration is complete. transfer total filtrate to a weighed evaporating dish and evaporate to dryness on a steam bath or in a drying oven. if necessary, add successive portions to the same dish after evaporation. Dry evaporated sample for at least 1 h in an oven at 180-2 c , cool in a desiccator to balance temperature, and weigh. repeat drying cycle of drying, cooling, desiccating,and weighing until a constant weigh is obtained or until weight change is less than 4% of previous weight or 0.5 mg, whichever is less. Analyze at least 10% of all samples in duplicate. Duplicate determinations should agree within 5% of their averege weight. if volatile solids are to be determined follow procedure in 2540E.