Specific gravity scales: Which scale is used exclusively for liquids heavier than water?

Introduction / Context:
Process engineers encounter several specific gravity scales in industry. Knowing which scale applies to which type of liquid simplifies interpretation of measurements in chemical plants and laboratories.

Given Data / Assumptions:

• Comparing well-known empirical scales: Baumé, Twaddell, API, and Brix.
• Water reference temperature is standard for the scales’ definitions.

Concept / Approach:
The Twaddell scale is defined for liquids heavier than water only. Baumé has two related scales (one for lighter-than-water, one for heavier-than-water liquids). API gravity is widely used for petroleum fractions, generally lighter than water. Brix measures sugar content, not specific gravity directly for generic liquids.

Step-by-Step Solution:

Verification / Alternative check:
Lookup relations: Twaddell degrees are proportional to (SG − 1) for SG > 1, aligning with the “heavier than water” restriction.

Why Other Options Are Wrong:

• Baumé: has heavy and light scales, not exclusive.
• API: oriented to petroleum liquids, which mostly have SG < 1.
• Brix: expresses percent sucrose equivalent; not a general SG scale.
• None of these: invalid given the correct Twaddell option.

Common Pitfalls:
Confusing Baumé’s dual definition with exclusivity, or mistaking API for a universal SG scale.

Final Answer:
Twaddell scale