METALLIC PROTACTINIUM The accompanying photomicrographs, although not particularly spectacular in appearance, have historical significancr in that they represent one of the first specimens of metallic protactinium ever produced. The preparation was made by A. V. Grosse, of The University of Chicago, and his assistants [see J.Am. Chem. Sor 56,220 (Oct., 1934)] by a method first introdnced by Langmuir [ibid., 37, 1139 (1915)l. The pentachloride was decomposed in a high vacuum on the surface of an electrically heated tungsten filament. Magnifications are about 40X and 100X, respectively. (Photographs by W. Borst.)
.
