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 (with washings) 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 weight 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 average weight. If volatile solids are to be determined, follow procedure in Section 2540E