AbstractThe dipole moments of nitrosyl chloride and nitrosyl bromide were determined as 1.83 ± 0.01Dand 1.87D, respectively. These values are compared to those estimated for a pure homopolar structure ClNO. The conclusion is reached that an ionic structure: Cl−[N≡O]+makes a considerable contribution to the stationary state. This type of resonance, already deduced from a discussion of bond distances, is thus confirmed.The dielectric constant of the pure liquid was found to be ϵ = 18.2 at 12° for NOCl and ϵ = 13.4 at 15.2° for NOBr,