Spiral Morphology of Boron Particles

NATURE 724 than for the cases just discussed, and the observed (small) ••Mo* activity from this reaction is not unexpected. It can be readily seen from the table that the (d,p) reaction is certainly not more promising than the (n,2n) reaction and probably less. So far, only reactions have been considered in which the initial nucleus had zero spin. For (p,n) and (d,2n) reactions the initial 93Nb nucleus has a spin of 9/2. The resulting higher spin intermediate states which are thus obtained favour transitions to the isomeric state. For example, even if we assume s-state protons and neutrons in the (p,n) reaction, inte.r mediate states of spin 7/2(0·20), 9/2(0·47) and 11/2(0·33) will be formed, with the weight of each spin shown in brackets. This shows clearly why the ••Mo* state is reached in these two reactions and not in the others. L. KATZ J. GOLDEMBERG Department of Physics, University of Saskatchewan, Saskatoon, Saskatchewan. April 9. Alburger, D. E., and Thulin, S., Phvs. Rev., 89, 1146 (1953~. ' Boyd , G. E., and Charpic, R. A., Phys. Rev., as, 681 (1952). 'Kundu . Holt and Pool, Phys. Rev., 71, 71 (1950). • Duffield, R. B., and Knigh t , J. D., Phv•. Rev., 76, 573 (1049). • Montalbetti, Katz and Goldemberg, Phys. Rev., 91, 659 (1953). 'Goldhaber, M., and Sunyar, A. W., Phys. Rev., 83, 906 (1951). 'Katz, Baker and Montalbetti, Can. J. Phys., 31, 250 (1953). • Katz, Pease and Moody, Can. J . Ph11•.. 30, 476 (1952). 'Goldhaber, M., and Hill, R. D., Rev. Mod. Phys., 24, 179 (1953) 10 Goldhaber, M., Phys. Rev., 89, 1146 (1953). "Muehlhause, C. 0., Phys, Rev., 79, 277 (1930). 1 Spiral Morphology of Boron Particles IN recent work on the ultimate analysis of decaborane 1 the permeability of palladium to hydrogen was utilized to separate the elements formed in the pyrolysis of this compound. Decaborane, contained in sealed palladium capsules, was decomposed by heating at 900° C., leaving a solid pyrolysis residue Fig. 2. October 17, 1953 voL. 112 Boron particle from pyrolysis of decaborane (dark-field Illumination. x 80) of boron containing approximately O·5 atom per cent palladium. The residue was in the form of hard, shiny black granules (0·5-1 ·0 mm.), the X-ray diffraction pattern of which consisted of three diffuse rings. Microscopic examination disclosed that many of the particles possessed an external spiral morphology, as shown in Fig. 1. This is more clearly seen in the photomicrograph (Fig. 2) prepared by Dr. F. H. Horn, of this laboratory. The spiral lacked the sharp step heights usually observed in the spiral growth patterns of crystalline materials. It more closely resembled a rolled-up rug viewed end on. At present we can offer no conclusive mechanism for the growth process which produced this unusual external morphology unaccompanied by any X-ray crystallinity. Pyrolysis of anthracene under the same conditions produced a non-crystalline carbon residue with no regular external structure. EDWARD L. SIMONS Research Laboratmy, General Electric Company, Schenectady, N.Y. June 15. • Simons, E, L., Balis, E. W., and Llebhafsky, H. A., Anal. Chem., 25, 635 (1953). Structure of Porphyrilic Acid IM Fig. 1. Boron particles from pyrolysis of decaborane PoRPHYRILIC acid, a sparingly soluble acid of high melting point (approx. 298° after darkening from 270°), was isolated by Zopfl from the crustaceous lichens Haematomma porphyrium (Pers.) and H. coccineum (Dicks.). Both lichens contained other acids, the latter, for example, ( - )usnic acid. Porphyrilic acid, for which no analyses were given, was characterized by an intense indigo-blue colour reaction with ferric chloride and a green colour with a solution of bleaching powder. On thermal decomposition, porphyrilic acid yielded a characteristic product, porphyrilin. An acid, undoubtedly identical with porphyrilic acid, has now been isolated together with lrevorotatory usnic acid from a lichen material consisting essentially of H. coccineum. The acid is extremely sparingly soluble in most organic solvents and is conveniently purified through its cyclohexylamine salt, © 1953 Nature Publishing Group  (...truncated)