A simple 3-parameter fit to experimental vapour pressures measured over a restricted temperature range:

log P = A - T + C

where A, B, and C are "Antoine coefficients" that vary from substance to substance. Sublimations and vaporizations of the same substance have separate sets of Antoine coefficients, as do components in mixtures. The Antoine equation is accurate to a few percent for most volatile substances (with vapour pressures over 10 Torr).