  In a recent propposal, the cosmological constant has been considered as as a
new thermodynamical variable and its change is related to the radiation
produced by black holes. Using this consideration and by modelling the
primordial black holes as Schwarzschild-de Sitter holes,we have constrained the
total mass of primordial black holes evaporated by now, giving an estimate of
the order of 1.624x10^24 solar masses.
