Mixtures of substances, comprising (A) vinyl monomers and (B) a mixture designed to inhibit premature polymerisation of (A) during purification or distillation, containing (i) 0.05-4.5 wt.% sec. amine N-oxide compound(s) with no hydrogens on the alpha -carbon atoms, and (ii) 99.95-95.5 wt.% nitro compound(s). Also claimed is a method for inhibiting premature polymerisation of monomers (A) by adding mixture (B) or its components before or during purification or distillation.
