Possible tests of neutrino maximal mixing and comments on matter effects

We show in a simple and general way that matter effects do not contribute to the average value of the transition probabilities of solar nu(e)'s into other states in the case of maximal mixing of any number of massive neutrinos. We also show that future solar neutrino experiments (Super-Kamiokande and SNO) will allow to test the model with maximal mixing of three massive neutrinos in a way that does not depend on the initial solar neutrino flux.