Volatility testing by Reid method: In the Reid vapor pressure (RVP) apparatus for petrofuels at 100°F, what is the ratio of the air (vapor) chamber volume to the liquid fuel chamber volume?

Introduction / Context:
Reid vapor pressure (RVP) is a legacy yet widely referenced measure of fuel volatility. The test uses a sealed apparatus with a defined vapor-to-liquid volume ratio to standardize the partial pressure measured at 100°F (approximately 37.8°C).

Given Data / Assumptions:

• Standard RVP test temperature: 100°F.
• Measurement in a closed volume with specified vapor and liquid chambers.
• Fuel equilibrated with its own vapor plus small air space.

Concept / Approach:
The Reid method specifies a vapor-to-liquid chamber volume ratio of 4:1. This ensures reproducible vaporization and pressure reading across labs and fuels.

Step-by-Step Solution:

Verification / Alternative check:
ASTM procedure descriptions and refinery handbooks state the 4:1 vapor-to-liquid volume ratio for the Reid bomb.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing Reid vapor pressure (legacy) with true vapor pressure (TVP); the apparatus ratio is specific to the Reid method.

Final Answer:
4