Flash point testing methods: The Pensky–Martens closed-cup apparatus is used for oils whose flash points are in which range (°F)?

Introduction / Context:
Flash point is the lowest temperature at which vapors above a liquid ignite momentarily on exposure to a flame. Different standardized apparatus are specified for different volatility ranges to ensure safety and reproducibility.

Given Data / Assumptions:

• Pensky–Martens is a closed-cup method.
• Used for medium-to-high flash point petroleum products (e.g., fuel oils, lubricants).
• Temperature range expressed in °F per the options.

Concept / Approach:
Closed-cup methods generally yield lower (more conservative) flash points than open-cup, and specific methods cover specific ranges. Pensky–Martens is intended for products with flash points typically above about 120 °F (≈ 49 °C). For very low flash points, other apparatus (e.g., Abel, Tag) are used.

Step-by-Step Solution:
Identify method applicability: medium/high flash point oils.Map to range: above 120 °F.Select the correct option: '>120' °F.

Verification / Alternative check:
Standards (ASTM D93) specify Pensky–Martens for a wide range that includes and emphasizes higher-flash products; low-flash gasoline-range materials use other tests (e.g., ASTM D56 Tag).

Why Other Options Are Wrong:
Ranges below 120 °F correspond to low-flash fuels requiring alternate apparatus; 90–110 °F is too low for the typical Pensky–Martens selection.

Common Pitfalls:

• Confusing open-cup vs. closed-cup results; closed-cup values are typically lower for the same liquid.
• Applying the wrong standard method outside its validated range.

Final Answer:
>120