X-ray computer axial tomography is a well established technique for producing images which show the spatial variation of X-ray linear attenuation coefficient within an object. X-ray differential K absorbtion edge tomography is the application of computer axial tomography to form images of selected atomic elements within an object, and these images show the distribution of specific atomic element concentration. The technique is to measure the attenuation of X-rays on either side of the K absorbtion edge of an atomic element with an energy dispersive X-ray detector, and then reconstruct an image of the location and concentration of that element in an object by means of a computer algorithm for display on a colour monitor. This method is able to image several atomic elements in one X-ray scan only of the object, in particular, consecutive elements in the Periodic Table of the Elements. One atomic element only within the object may be better selected by correcting for the X-ray attenuation of all the other elements, the matrix of the object, by extrapolating the measurements to the K absorbtion edge, thus measuring accurately the absorbtion coefficient of the analyte element only. The concentration of analyte element may O be measured down to about lkg/m in a water like matrix with a total of 108 photons. Herein is described the construction of an X-ray machine as a differential K absorbtion edge spectrometer, and the application of this technique to image three chosen atomic elements, 46Palladium, 47Silver, and 48Cadmium using the spectrometer. Experiments which showed that this technique works, and possible further development of the spectrometer, are also described.