Chromite (FeO·Cr2O3) refractories: select the correct use cases from the options given.

Introduction / Context:
Chromite refractories are often considered “neutral” with useful resistance to both acidic and basic environments. They are used in steel industry applications where chemical compatibility and thermal shock resistance are essential.

Given Data / Assumptions:

• Soaking pits: exposure to high temperatures and variable atmospheres.
• Open-hearth furnaces: require barrier layers to prevent reaction between basic and acidic linings.
• Chromite’s neutrality and hot strength are advantageous in these roles.

Concept / Approach:
Using chromite at the base of soaking pits gives good structural performance and corrosion resistance. As an interlayer in open-hearths, it mitigates chemical interactions at the interface between incompatible lining chemistries, improving campaign life.

Step-by-Step Solution:
Check (a): Common application — acceptable.Check (b): Well-known design practice — acceptable.Hence select “Both (a) & (b)”.

Verification / Alternative check:
Traditional furnace lining guides list chromite as neutral interlayers and for pit bottoms due to its balance of properties.

Why Other Options Are Wrong:
Single selections omit the other valid application; “neither” is false.

Common Pitfalls:
Confusing chromite with chrome–magnesite (basic) bricks; chromite alone is closer to neutral behavior.

Final Answer:
Both (a) & (b)