Dipole moments and molecular structure. Part II.—The trichlorides of the elements of group V

Although numerous investigators have carried out measurements of the dipole moments of the commoner organic compounds, few references are to be found to analogous data for inorganic compounds. The latter are confined almost exclusively to those substances which can be investigated in the gaseous state. The present series of investigations were commenced, therefore, with a view to applying the method of dilute solutions to the measurement of the dipole moments of such inorganic compounds as are soluble in non-polar solvents, and to relating the dipole moments of analogous groups of compounds to their molecular structures. The first series of measurements to be made, and those described in this paper, were upon the trichlorides of phosphorus, arsenic and antimony. Of these, measurements had been recorded only with respect to antimony trichloride when this investigation was carried out. More recently, measurements of the dipolar moments of all three compounds have been recorded by Bergmann and Engel. but their experimental results show much greater discrepancies among one another than do those of the author. Werner used both benzene and ethyl ether as solvents for the antimony trichloride, finding a considerable difference between the values obtained in the two cases. Bergmann and Engel used carbon tetrachloride as solvent for the phosphorus and arsenic trichlorides and benzene for the antimony trichloride. In the present investigation, benzene has been used as the solvent for all three compounds.