A replica technique has been developed for the electron microscope study of particles of precipitates formed by mixing solutions of chemical reagents. The replica is formed thermally in a thin film of parlodion. A one‐step, shadowed replica has been found most satisfactory. The technique has been found suitable for studies of the effect of conditions of observation upon the specimen materials, studies of precipitates such as silver chloride which are known to be unstable during direct observation, studies of precipitates as they exist in the mother liquid; and studies which require detailed observation of surfaces.