Specific gravity scales: Which scale is used exclusively for liquids heavier than water?
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ABaumé scale
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BTwaddell scale
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CAPI gravity scale
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DNone of these
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EBrix scale
Answer
Correct Answer: Twaddell scale
Explanation
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:
Identify the scale restricted to heavy liquids: Twaddell.Confirm alternatives: Baumé is dual; API is for hydrocarbons (lighter); Brix is sugar concentration.Therefore, the correct choice is Twaddell scale.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