[en] X-ray observations of quasars obtained with the IPC detector aboard the Einstein satellite are presented. The total X-ray flux in the range 0.5-3 keV and the hardness ratio are given as well as the derived luminosity, the X-ray power law spectral index and the hydrogen column density on the line of sight resulting from a detailed spectral fitting of the data. Correlations between the X-ray spectrum and some parameters of optical emission lines were looked for, but none was found with the Hβ equivalent width or full-width half maximum. An anticorrelation of hardness ratio with the equivalent width of the optical Fe II emission line was discovered. The averaged hardness ratio was found to be lower (softer spectrum) for radio quiet than for radio quasars. This difference is related to the previous correlation, most of radio quiet quasars being strong Fe II emitters. (Auth.)