Flash point testing: for middle distillates such as diesel and kerosene that typically have flash points greater than 50°C, identify the standard apparatus used to determine flash point under closed-cup conditions.

Introduction / Context:
Flash point is a key safety property indicating the lowest temperature at which a fuel emits sufficient vapour to ignite momentarily under test conditions. For middle distillates like kerosene and diesel—whose flash points are generally above 50°C—industry standards prescribe specific test apparatus and procedures to ensure reliable, comparable results.

Given Data / Assumptions:

• Fuel: diesel or kerosene with flash point typically > 50°C.
• Testing environment: standardized closed-cup method.
• Objective: select the correct apparatus name.

Concept / Approach:
The Pensky-Martens closed-cup apparatus is widely used for measuring flash points of middle distillates and heavier oils because it minimizes vapour losses and better reflects storage and handling conditions. The Abel apparatus is commonly used for lower-flash, more volatile products. The Saybolt chromometer is not a flash point device; it measures colour (Saybolt colour scale) of light petroleum products.

Step-by-Step Solution:

Verification / Alternative check:
Fuel standards (e.g., for diesel/kerosene) reference Pensky-Martens for specification compliance, ensuring consistency across laboratories.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing open-cup and closed-cup methods; closed-cup generally gives lower flash points due to containment of vapours.

Final Answer:
Pensky-Martens apparatus