In a common lab measurement experiment, the crucible is heated before adding the hydrated sulfate to ensure it is clean and dry

. This is achieved by heating the crucible in the flame of a Tirrell burner until it reaches a constant weight

. The crucible is then cooled in a desiccator and weighed

. This process of heating, cooling, and weighing is repeated until successive weighings agree within 0.2 mg

. Here's a more detailed breakdown:

1. Cleaning : The crucible is first cleaned

2. Heating : The crucible is heated using a Tirrell burner, with the flame's tip just below but not touching the crucible

. The crucible is heated to a red heat for 5-10 minutes

. Alternatively, a Bunsen burner can be used to strongly heat the crucible for several minutes

3. Cooling : The crucible is allowed to cool for a few minutes before being placed in a desiccator to reach room temperature

4. Weighing : The crucible is weighed accurately to ± 0.1 mg

5. Repetition : The heating and weighing process is repeated until successive weighings are within 0.2 mg of each other, ensuring a constant weight