All of our structure-factor coding utilizes the general form of the structure-factor expression so that no special coding is needed for particular space groups. Consequently, the above expressions may be used directly, in the form of 'code words' (Sparks et al., 1956)

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We describe some attempts to observe magnetic structure in various actinide (5f-electron) materials. Our experimental technique is neutron powder diffraction as practiced at a spallation (pulsed) neutron source. We will discuss our investigations of α-Pu, δ-Pu, α-UD3, and β-UD3. β-UD3 is a simple ferromagnet: Surprisingly, the moments on the two nonequivalent uranium atoms are the same within experimental error. α-UD3, α-Pu, and δ-Pu are nonmagnetic, within the limits of our observations. Our work with pulsed neutron diffraction shows that it is a useful technique for research on magnetic materials.

Hydrazinium fluoborate, NH~-NH~BF~-crystallizes in a monoclinie form in space group C2/c (or Cc). The unit-cell dimensions and atomic positional parameters x and z are reported here.Hydrazinium fluoborate was prepared by neutralizing a 15% solution of hydrazine in 2-propanol with a 50% aqueous solution of fluoborie acid to a methyl red end-point. The product solution was evaporated to dryness and the residue recrystallized from 2-propanol. The crystals appeared as blunt rods elongated parallel to the unique axis, b.Rotation and Weissenberg photographs around b were taken with Cu Ka radiation. The length of the b axis was estimated from the rotation diagram and the parameters a, c and fl were taken from the Weissenberg films. considered. After five least-squares cycles, R minimized at 21%. The resulting parameters are shown in Table 1.The systematic absences of hkl with (h +k) odd, and hO1 with 1 odd suggest that the structure belongs in space group C2/c (No. 15) or Cc (No. 9). We have assumed the former.A crystal with cross section 0.4 × 0.4 mm was cleaved to a length of 0.6 mm and was mounted in a glass capillary with the rotation axis parallel. This crystal was used for the preparation of three-film Weissenberg photographs of the hOl layer. The intensities were estimated visually by comparison with a calibrated strip prepared from the same crystal, and were adjusted for the Lorentz and polarization effects. A sharpened vector map with the origin suppressed was made with the Patterson function. The x and z trial parameters of the (010) projection were determined from the vector map and from knowledge of the probable molecular configuration.They were refined by use of the Gantzel, Sparks & Trueblood (1961) Least Squares Refinement Program for the IBM 7090 computer. An isotropic temperature factor was refined for each atom. The hydrogen atoms were not