Flash Point Estimator
Estimate the flash point of an organic liquid from its normal boiling point using the Satyanarayana-Rao correlation.
Also classifies the flammability hazard category.
The flash point is the lowest temperature at which a liquid produces enough vapor to briefly ignite when an ignition source is present. It is one of the most important safety parameters for handling flammable liquids.
Measuring flash point requires specialized equipment (Pensky-Martens closed cup or Tag closed cup). When measured values are unavailable, the flash point can be estimated from the normal boiling point Tb using the Satyanarayana-Rao correlation:
Tf = 0.683 * Tb - 119.4 (temperatures in Kelvin)
Converting to Celsius: Tf(C) = 0.683 * (Tb(C) + 273.15) - 119.4 - 273.15
This correlation works well for non-polar organic liquids (alkanes, aromatic hydrocarbons, esters) and has an average error of about 4-6 C. It is less accurate for alcohols, amines, and other hydrogen-bonding compounds, which tend to have higher flash points than the correlation predicts.
Flammability classification (GHS / OSHA):
- Category 1: flash point below -23 C and boiling point at or below 35 C (e.g. diethyl ether -45 C)
- Category 2: flash point below -23 C and boiling point above 35 C
- Category 3: flash point -23 C to below 23 C (e.g. acetone -20 C, ethanol 13 C)
- Category 4: flash point 23 C to 60 C (e.g. diesel ~60 C, kerosene 37-65 C)
- Non-flammable: flash point above 60 C (e.g. most vegetable oils 250-300 C)
Never rely solely on estimated flash points for safety decisions – always verify with measured values before handling unknown materials.