To the problem of determining the structure of naphthalene have been applied many methods, physical and chemical. Among the physical methods may be mentioned, measurement of dipole moments, refractivities, and X -ray spectra. It is intended in this thesis, to deal with the subject chiefly from the evidence obtained from chemical reactions. In spite of innumerable researches the structure of naphthalene still remains indefinite. From evidence obtained here and from the work of previous authors it was concluded that the nature of the substituents on an aromatic ring had a powerful influence on the arrangement of bonds in the ring and therefore although our results with regard to the naphthalene series were in agreement with the Erlenmeyer formula for naphthalene we do not consider ourselves justified in claiming this work to be evidence in favour of. the Erlenmeyer formula for an unsubstituted naphthalene molecule.