Interpreting aniline point for diesel: A high aniline point value for a diesel sample most strongly indicates that the fuel is:

Introduction:
The aniline point is the minimum temperature at which equal volumes of aniline and the test oil are completely miscible. It serves as a proxy for aromaticity: aromatics dissolve more readily in aniline, so aromatic-rich fuels have lower aniline points; paraffinic fuels require higher temperature to mix and therefore have higher aniline points. This question asks what a high aniline point implies for diesel fuel composition and behaviour.

Given Data / Assumptions:

• Equal-volume aniline mixing test.
• We correlate aniline point with hydrocarbon family predominance.
• Typical diesel-range hydrocarbon distribution is assumed.

Concept / Approach:
A high aniline point indicates low aromatic content and a more paraffinic character. Paraffinic diesel typically exhibits higher cetane number and shorter ignition delay, not the reverse. Diesel index (an empirical quality metric) tends to be higher for paraffinic, low-aromatic fuels, aligning with higher aniline points.

Step-by-Step Solution:

Verification / Alternative check:
Specifications and textbooks often correlate aniline point with diesel index and cetane: higher AP coincides with improved ignition quality and reduced aromaticity.

Why Other Options Are Wrong:

• Highly aromatic: Would imply low AP, not high.
• Large ignition delay: Paraffinic fuels tend to have shorter ignition delay.
• Low diesel index: Contradicts the positive correlation with high AP.
• Dominated by PNAs: Again implies low AP.

Common Pitfalls:
Assuming higher AP means better solvency in aniline; it actually means the opposite at low temperature, signalling lower aromatic content.

Final Answer:
Highly paraffinic