When Method A is used, the test is complete when the change in mass does not exceed 0.01 percent for three consecutive minutes.

• A. False
• B. It ends after 5 minutes
• C. True
• D. Only for certain samples

Answer: (C)

The test uses a mass-stabilization criterion. In Method A you monitor how the sample’s mass changes over time as it dries or undergoes processing, and you declare the test finished only when the mass has stabilized to a very small change—no more than 0.01 percent—for three consecutive minutes. This tight tolerance ensures that all moisture and transient losses have essentially ceased, so the final mass (and any calculations based on it) reflects the true, stable value rather than ongoing change. Requiring three straight minutes of stabilization guards against stopping the test during a brief pause in fluctuation, giving confidence in the result. The time isn’t fixed at a specific duration like five minutes; if the sample hasn’t stabilized within that 0.01%/three-minute window, you keep testing. This criterion is a standard, general rule for Method A, not something limited to particular samples.