Question

In order to determine moisture content by oven drying method, the sample is kept in the oven fixed at a temperature of:

• A. 105 \(^{\circ}\)F
• B. 120 \(^{\circ}\)F
• C. 105 \(^{\circ}\)C
• D. 140 \(^{\circ}\)C

Hint:

Always pay attention to units. Options are given in both Fahrenheit and Celsius. 105\(^{\circ}\)C is the standard. Temperatures much higher than 110\(^{\circ}\)C can burn off organic matter, while temperatures below 100\(^{\circ}\)C will not effectively remove all the water.

Answer 1

The Correct Option is C

Step 1: State the purpose of the oven drying method. The goal is to remove the water from the soil pores by evaporation without altering the soil's chemical composition, particularly by not burning the organic matter present.
Step 2: Identify the standard temperature range. The standard temperature for drying soil samples is maintained between 105\(^{\circ}\)C and 110\(^{\circ}\)C. This range is chosen because it is safely above the boiling point of water (100\(^{\circ}\)C), ensuring efficient evaporation, but below the temperature at which soil organic matter begins to char or decompose, which would lead to an inaccurate measurement of the dry soil mass.