(1) The influence of substitution on the formation of a furan-ring has been compared among o′,o′-biphenol and its nitro, bromonitro and bromo derivatives, the following results being obtained in the case of reactions between dry carbonate of barium or sodium and the diacetoxydiphenyls derived from those biphenols. (i)The introduction of nitro groups into the diacetoxydiphenyls facilitates the removal of acetyl groups of those compounds and also the formation of the furan-ring. This facilitating effect varies with the relative position of the nitro group and the acetoxyl group, the order of the effect being ortho>para>meta; but the m-nitrosubstitution induces no ring-formation, giving exclusively nitrobiphenols. (ii) The introduction of bromine into the diacetoxydiphenyls hinders the removal of the acetyl groups and also the formation of the furan-ring, no bromobiphenylene oxide being obtained. This effect is more remarkable in the case of o-substitution than in that of p-one relative to the acetoxyl groups. (2) The effect of nitrosubstitution on the opening of the furan-ring of biphenylene oxide in caustic soda solution was also studied, and it was found that the introduction of the nitro groups facilitates the ring-opening, and this facilitating effect varies with the relative position of the nitro group and the oxygen atom of biphenylene oxide, the order of the effect being ortho>para>meta. This effect appears to be proportional to the electrolytic dissociation degree of nitrobiphenols obtainable from the nitrobiphenylene oxides. (3) In the course of these experiments, two nitrobiphenols and seven bromonitrobiphenols were newly prepared.