We determine the liquid-vapour coexistence curve of the restricted pri
mitive model of electrolytes by means of Monte Carlo simulations perfo
rmed in the Gibbs ensemble and in a hyperspherical geometry. It is fou
nd that the Stillinger-Lovett condition is satisfied in the liquid pha
se but not in the vapour phase. This means that the latter could be di
electric. Whether this unexpected result is due to finite-size effects
or not remains an open question.