Metallurgical analysis techniques: Which analytical instrument can be used to determine the composition of metallic alloys (after suitable sample preparation and dissolution where required)?

Introduction / Context:
Alloy composition analysis can be performed by several instrumental methods. In classical chemical engineering and metallurgy exam contexts, a polarograph—an electroanalytical instrument—has long been cited for quantifying metal ions in solution obtained by dissolving alloy samples. This question aligns with that conventional viewpoint.

Given Data / Assumptions:

• Solid metallic alloy can be dissolved to form ionic species.
• We seek an instrumental technique suitable for quantifying constituent metals.
• Exam framing favors traditional instruments over advanced spectrometry.

Concept / Approach:
Polarography (a branch of voltammetry) measures current as a function of applied potential at a dropping mercury or static electrode. Distinct reduction/oxidation waves appear at characteristic potentials for different ions, and wave heights are proportional to concentration. Thus, after dissolving an alloy, its components can be quantitatively determined.

Step-by-Step Solution:

Verification / Alternative check:
While emission spectrometry or XRF are widely used today, classical exam answers often specify polarography as a valid laboratory method for alloy analysis after dissolution.

Why Other Options Are Wrong:

• Chromatograph: Excellent for separations, but metals as elemental ions are not typically separated by standard GC/LC without complexation chemistry; it is not the canonical choice for alloys.
• Refractometer: Measures refractive index of liquids; not suitable for metals.
• Colorimeter: Works for colored complexes but is less general than polarography for multi-component alloys.

Common Pitfalls:
Assuming a solid metal can be tested directly by chromatograph or refractometer; appropriate dissolution and electroanalytical methods are key.

Final Answer:
Polarograph