Muffle Furnace
An electrically heated, insulated chamber that reaches several hundred to over 1000 °C. In QC it is used to ignite samples for sulphated ash (residue on ignition) and to bring crucibles to constant mass.
- Pharmaceutical
- Food
- Cement and ceramics
- Mining
- Environmental
Test your Muffle furnace knowledge
Multiple-choice questions
Pick an answer to see whether you are right and why.
Q1. At what temperature is the sample ignited for sulphated ash?
basicQ2. Where in the furnace should crucibles be placed?
basicQ3. What is used to check muffle furnace temperature accuracy?
intermediateQ4. Why is the sample charred before placing it in the hot furnace?
intermediateQ5. Where should hot crucibles be cooled before weighing?
basic
Viva questions
Think of your answer first, then open it to compare.
1. What does 'ignite to constant mass' mean?
Heating, cooling and weighing are repeated until two consecutive weighings agree within the small limit in the chapter or SOP (commonly 0.5 mg).
2. What safety precautions do you take when loading a muffle furnace at 600 °C?
Wear heat-resistant gloves and a face shield, use long tongs, place crucibles quickly in the centre, keep flammables away and put hot crucibles on a heat-proof tile before the desiccator.
Keep every Muffle furnace in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.