Dependence on Reddening of Interstellar Column Densities in the Direction of O-Stars

We have investigated 14 O-type stars with IUE high resolution SWP spectra in order to improve the relations of element depletions withE(B-V), and to look for other possible relations with two stellar parameters: namely, the rate of mass loss and rotational velocity. The stars were chosen so as to cover several directions in the Galaxy, as well as a wide range in interstellar reddening. Although our data are only crude and were obtained by making several approximations, they show the derived dependence of a parameter, which we call a depletion index, on reddening. We found a clear inverse trend relating the abundance of elements to interstellar reddening, and a crude relation between the increasing depletion and condensation temperature.