This quantity, estimated from a Wildman-Crippen model, is plotted against a surface area in a plot backronymically named for resembling a boiled egg. pKa and this dimensionless quantity are predicted in SAMPL blind challenges. The ratio of this quantity to a reference state determines a Hansch-Fujita pi constant. A lowercase c prefixes this quantity when ADME software estimates it using group contributions. The shake-flask method measures this quantity, which ought to be less than 10 to the (*) fifth according to Lipinski’s rules. QSAR prioritizes compounds for which (10[1])the log of this quantity is negative. This proxy for bioavailability increases linearly with a drug’s lipophilicity. For 10 points, what ratio measured by liquid-liquid extraction characterizes if a drug diffuses into octanol or water? ■END■