A semiquantitative treatment predicts that when an electrohydrodynamic capillary source produces metal droplets along with the ions that are generally observed, the charge-to-mass ratio will reach a maximum and the radius a minimum at about the radius at which the limit of stability against breakup into smaller drops (Rayleigh limit) becomes equal to the limit of stability against the field evaporation of ions. The maximum charge-to-mass ratio was found to be [inverted lazy s] 17 000 C/kg for a eutectic mixture of lead and bismuth. The semiquantitative treatment, which is supported by this experimental result, predicts that the ions should be emitted from a liquid tip having a radius of about 10 Å. It is suggested that if the wobble of the tip is not too great, this type of source should have applications in ion microprobes.