From an analysis of electron pulses in liquid argon produced by α particles the average energy required to form an ion pair is evaluated, assuming Jaffé's theory of columnar recombination is valid. The mean value of 26.0 eV found in this way agrees well with the corresponding value of 26.4 eV for α particles in argon gas. Application of Jaffé's theory to the liquid state is discussed, and from the pulse distributions it is established that the experimental results are in good agreement with this theory.