Which adjustment is required when uncoated particles are present to determine sample volume?

• A. Use SSD weight in air
• B. Dry the surface water only
• C. Dry the surface water and use SSD weight instead of weight in air
• D. Weigh in water

Answer: (C)

When determining sample volume from mass measurements, moisture on the surface of uncoated particles can bias the result. Water clinging to the surface adds weight without contributing to the particle’s actual volume, so using a plain weight in air gives an inflated mass and an incorrect volume calculation. Drying off the surface water and using the saturated surface-dry (SSD) weight in air provides a consistent, representative mass for the solid, eliminating the misleading surface moisture. This SSD-based mass is then used with the appropriate weight-in-water measurement to determine volume accurately. In short, remove surface moisture and rely on the SSD weight in air rather than a simple weight in air.