The Possibility of distinguishing between Substances shown on Electron Micrographs

Abstract

THE electron microscope can be used to investigate the morphological features of a specimen right down to the molecular level, but there is as yet no way of identifying the chemical nature of the substances seen, except on the rare occasions when these happen to be crystalline. In a specimen of uniform thickness, a region of high electron opacity may, in general, be said to be one containing substances of a greater weight density than those of the surrounding less opaque region¹, but this gives little help in deciding on their chemical composition. The lack of any direct way of knowing what substances one is looking at is perhaps the most serious shortcoming of electron microscopy.