AbstractSolid solutions of cadmium sulf ide and cadmium selenide prepared by several methods at temperature in excess of 1000°C in inert atmosphere are described. The compositions of these solid solutions varied widely, ranging from pure cadmium sulfide to pure cadmium selenide.Films of solid solutions have been successfully prepared by the vacuum deposition on various substrates using a procedure previously reported. Conditions for the depositions have been investigated to prevent noticeable alteration of the composition of the solid solution dur ing vacuum deposit ion. Films of various thicknesses have been prepared to date.Determination of film thicknesses have been carried out by the fluorescence method based on the elements existing in these solid solutions. Chemical analysis in which specimens were consumed have also been used primarily for the construction of calibration curves. X-ray fluorescence intensity versus film thickness are established for films of 0, 25, 50, 77, and 100 percent by weight of cadmium selenide up to 10.00 microns thick on aluminum substrates. Thickness determinations using selenium Kαand cadmium Kαspectra give accuracies of 0.200 ± 0.05 to 10.00 ± 0.40 microns depending on film thickness and composition. Correction factors are given for films on substrates other than aluminum.Procedures have been established for the determinat ion of both composition and film thickness based on fluorescence intensity data. There is a relationship between the fluorescence intensity and appearance when deposited films are not of the same thickness. Correlation of these phenomena will be demonstrated.