UPSC Combined Geo-Scientist, Mains · 2022 · Mains Paper III
Q1(e). Components of a thermogravimetric analyser
Question
Mention the different components in the instrument for thermogravimetric analysis.
Answer in brief
A thermobalance: a recording microbalance, a furnace, a sample holder, a temperature programmer with a thermocouple, a purge-gas system and a data system recording mass against temperature.
Key points
- Recording microbalance: null-point electromagnetic balance; the coil current that restores the beam measures the mass; sample 5–20 mg.
- Furnace: ambient to 1000–1600 °C; the balance is thermally isolated from it.
- Sample holder (crucible of Pt, alumina or quartz) hung from the balance arm inside the furnace.
- Temperature programmer with a thermocouple close to the sample: linear heating 0.5–50 °C min⁻¹, or isothermal.
- Purge-gas control (N₂, Ar, air or O₂) and a data system recording the thermogram (TG) and its derivative (DTG).
The full model answer
As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.
Coversthermogravimetric analysisthermobalancemicrobalancefurnacepurge gasTG DTG
All parts of Question 1
- 1(a) Accuracy and precision5 marks
- 1(b) Phases in GLC and choice of carrier gas5 marks
- 1(c) Matching techniques with sources and detectors5 marks
- 1(d) Cold-vapour atomisation for mercury5 marks
- 1(e) Components of a thermogravimetric analyser5 marks
- 1(f) X-rays from radioactive isotopes5 marks
- 1(g) Generation of the argon plasma in ICP–MS5 marks
- 1(h) Manganese in pyrolusite by redox back-titration5 marks