Dry the sample to a constant mass in an oven regulated at 110 ± 5 °C (230 ± 9 °F) and determine the initial sample weight to the nearest 0.1%.

• A. The sample is dried at 85 ± 5 °C and initial weight to the nearest 0.1%
• B. The sample is dried at 100 ± 5 °C and initial weight to the nearest 0.1%
• C. The sample is dried at 105 ± 5 °C and initial weight to the nearest 0.1%
• D. The sample is dried at 110 ± 5 °C and initial weight to the nearest 0.1%

Answer: (D)

Using a controlled oven temperature to dry the sample to constant mass is about removing moisture consistently without altering the sample itself, so the mass you measure reflects only the moisture being evaporated. The specified temperature range of 110 ± 5 °C keeps drying standardized across labs and prevents overheating that could drive off binder or degrade materials, which would distort results. If the temperature is noticeably lower, drying happens slowly and may leave moisture; if it’s outside the tolerance, the rate and extent of drying become unreliable. Reaching a constant mass means continuing drying and cooling until the mass no longer changes between weighings, confirming all free moisture is removed. Recording the initial sample weight to the nearest 0.1% gives enough precision for accurate calculations later, since small changes in starting weight directly affect the computed percentages. Therefore, the correct approach is to dry at 110 ± 5 °C and determine the initial weight to the nearest 0.1%.