X-ray spectra of four comets measured with Chandra X-Ray Observatory (CXO) have been uniformly processed and analyzed. Some tools have been developed that make it possible to extract abundances of C+5, C+6, O+7, O+8, and Ne+9 in the solar wind around comets from their X-ray spectra. Despite the low resolving power E/δE ≈ 5, quantitative spectroscopic analysis has been successfully applied to the CXO spectra of comets. The retrieved C+5 and O+7 abundances are corrected for contributions of the secondary ions produced by charge exchange of C+6 and O+8, respectively. The data from four comets reveal significant variability of the flow, chemical composition, and charge state in the solar wind. The C+6/C+5 ratios correlate with those of O+8/O+7 and indicate that the solar wind was slow near comet T1, fast near comets Q4 and Encke, and medium near comet S4. The mean temperature of Ne extracted from the Ne+9 abundances agrees with those from the O+8/O+7 ratios. The heavy ion flow in the solar wind varies from comet Q4 to comet T1 by a factor of 12 being near the mean value in comet Encke that was observed for a long exposure time. Coincidence of the O+8/O+7 ratios extracted independently from two line pairs and the excellent correlation between C+6/C+5 and O+8/O+7 demonstrate the high accuracy of the method. X-ray spectroscopy of comets may be used for diagnostics of the solar wind at large distances from the Earth.