Definitions of ignition temperatures for liquid petrofuels At which characteristic temperature is only a brief, momentary flashing observed when a test flame is applied to the fuel surface?

Introduction / Context:
Safe storage and handling of liquid fuels depend on understanding standard temperature definitions: flash point, fire point, and autoignition temperature. These are measured under controlled test methods to classify flammability hazards and set equipment and regulatory limits.

Given Data / Assumptions:

• We consider common closed- or open-cup flash point tests as defined in standards.
• Momentary ignition (a brief flash that does not sustain) is the behaviour of interest.
• We are not discussing combustion chamber flame temperatures or viscosity-related preheating.

Concept / Approach:
The flash point is the lowest temperature at which a liquid gives off sufficient vapour to form an ignitable mixture near its surface and momentarily flashes when a small flame is applied. The fire point is slightly higher, at which sustained combustion continues for at least several seconds. The other listed temperatures are unrelated to this specific definition.

Step-by-Step Solution:

Verification / Alternative check:
Standard test methods (e.g., Pensky-Martens closed cup) explicitly define the observation at flash point as transient.

Why Other Options Are Wrong:

• Fire point: Requires sustained combustion, not momentary flash.
• Flame temperature: Refers to combustion adiabatic flame values, unrelated to ignition test definitions.
• Preheating for 25 cSt: A burner handling condition, not an ignition property.

Common Pitfalls:
Using flash and fire point interchangeably; always distinguish transient vs sustained burning.

Final Answer:
Flash point