Factoriality of certain hypersurfaces of P4 with ordinary double points

Let V subset of P-4 be a reduced and irreducible hypersurface of degree k greater than or equal to 3, whose singular locus consists of 6 ordinary double points. In this paper we prove that if delta < k/2, or the nodes of V are a set-theoretic intersection of hypersurfaces of degree n < k/2 and delta < (k - 2n)(k - 1)(2) /k, then any projective surface contained in V is a complete intersection on V. In particular V is Q-factorial. We give more precise results for smooth surfaces contained in V.