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UPSC Combined Geo-Scientist

Chemist

  • 3 descriptive papers
  • 200 marks each
  • 3 h per paper

Mains Paper III covers analytical and organic chemistry.

UPSC Combined Geo-Scientist, Mains · 2023 · Mains Paper III

Q1(h). Type metal: constituents and non-destructive analysis

Question

What are the major constituents of type metal? Suggest a method for non-destructive analysis of the constituents in type metal. (Description of the method is not required)

Answer in brief

Type metal is an alloy of lead (major), antimony and tin; non-destructive analysis by X-ray fluorescence (XRF) spectrometry on the solid alloy.

Key points

  • Type metal = printer's alloy of lead (about 50–86 %), antimony (about 11–30 %) and tin (about 3–20 %); a little copper in some grades.
  • Typical grades: linotype Pb 84, Sb 12, Sn 4 %; stereotype Pb 80, Sb 14, Sn 6 %; monotype Pb 74, Sb 16, Sn 10 %.
  • Pb gives low melting point and fluidity; Sb hardens and cancels shrinkage; Sn improves fluidity and toughness.
  • XRF directly on the solid alloy: Pb from its L lines, Sb and Sn from their K lines, against alloy standards.
  • Also non-destructive: instrumental neutron activation analysis.

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.

Model answer to Q1(h), 2023 Mains Paper III: solution pages 9 and 10
Solution pages 9 and 10 of 40
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Topic notes: analysis of ores, alloys, petroleum, coal and coke (dolomite, bauxite, brass, Ni in steel, aniline point, proximate and ultimate analysis, calorific value), with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverstype metallead antimony tin alloyXRFnon-destructive analysisalloy analysis

All parts of Question 1