To obtain achievable volatile results, the following issues must be noted:

1、 The measurement temperature should be strictly controlled at 900 ± 10 ℃, for which it is necessary to:

（1） Regularly calibrate thermocouples and millivolt meters. When calibrating and using thermocouples, the cold end should be filled with ice water or the zero point should be set to room temperature, or a cold end compensator should be used;

（2） Regularly measure the constant temperature zone of the muffle furnace, and the crucible containing coal samples must be placed in the constant temperature zone of the muffle furnace.

2、 After putting the crucible containing coal samples into the muffle furnace, the furnace temperature should be restored to 900 ± 10 ℃ within 3 minutes. To achieve this, it is necessary to:

（1） The muffle furnace should regularly verify whether its temperature recovery rate meets the requirements, or it should be manually controlled to ensure compliance with the above requirements;

（2） It is best to place the same number of crucibles in each experiment to ensure that the thermal capacity of the crucibles and their supports is basically the same.

3、 The total heating time (including temperature recovery time) should be strictly controlled within 7 minutes;

4、 To use crucibles that comply with GB211 regulations, the lid of the crucible must be tightly fitted.

5、 A crucible frame made of heat-resistant metal should not peel when heated, as it may affect the measurement results if it gets stuck on the crucible.

6、 After taking out the crucible from the muffle furnace, the cooling time in the air should not be too long to prevent the coke residue from absorbing water