The combination of electron microscope and x-ray spectrometer is a very powerful tool. Not only can one see a sample in great detail, but one can determine, and even map, the chemical elements, in Part 1, I discussed some of the basics of energy dispersive x-ray spectroscopy (EDS, EDX). In Part 2,1 went into detail about the construction of the detector, and discussed counting statistics. In this installment I will discuss the interaction between the x-ray and the detecting crystal, things that can go wrong in the process, and the phenomena which can make false peaks in a spectrum.