X-rays can be physically reflected from surfaces under certain conditions and quantitative measurements of the reflected X-ray intensity around the critical angle for X-ray reflection may be utilized to provide a method for the chemical analysis of very thin surface layers or thin films including adsorbed organic films. This method of chemical analysis is based on different physical principles than the well-known X-ray diffraction or fluorescence methods. The X-ray reflection method for the chemical analysis of thin surface layers depends on the influence of the X-ray absorptivity of the surface layers upon the concommitant angular or wavelength dependence of the intensity of the reflected X-ray. Because the reflected wave does not significantly penetrate the sample, the sample depth for chemical analysis by the reflected X-ray beam can be very thin, for example about 100 angstroms in thickness.