In the refinements of the 250 and 268°C data, the occupancy of the alternate oxygen sites was a free parameter, and at 268°C it seems clear that there is partial occupancy of these sites. Above the 275°C transition, to refine the 290°C data we assumed equal occupancy of the 'e' sites and the alternative sites and allocated the two sets of oxygen atoms separate positions and thermal parameters. The low R value, and the agreement between the two sets of oxygen position parameters, support this hypothesis of the structure.The mean square vibration amplitude of Na, N and O atoms, calculated as 1(/./11-l-//22--~-/d33 ), is plotted against temperature in Fig. 1, together with the results of CHP. The spectacular increase in the O vibrations, reported by CHP, seems to be spurious. The 268 ° data gave anomalously low values for the vibration amplitudes and we suspect that this was caused by fairly intense diffuse scattering resulting in anomalous absorption.If the NOa group is rigid, then ul~ for N and O should be the same. Table 1 shows that this is indeed so, within the quoted error limits, up to 250°C. The rotational amplitude of the NOa group about the c axis (the 3-axis of our Cartesian system) is not unusually large (11.7 ° at 250°C).The bond length from the conventional refinements decreases with temperature due to the well-known apparent shortening due to arc motion. Refinements incorporating a proper formulation of this effect gave a more-or-less constant value of the N-O distance at 1.256 (1) A. The agreement with CHP on this point is excellent. Analysis of X-ray dataTaking the thermal and positional parameters at room temperature from this experiment, and the X-ray data of Inkinen and CHP (put on a common scale by separate refinements), we prepared difference Fouriers.The X-ray form factors of Na+N2+O3 and of Na+NS+O 2-were calculated after Clementi (1965). These difference Fouriers appeared, however, to show no systematic features which could be interpreted as clear information on the ionic state or bonding within the NO3 group. We concluded that more accurate X-ray data would be needed to explore this question. The crystal structure of p-nitrophenyl acetate, CaHTNO4, is monoclinic, P21/c, a= 14-115 (10), b= 7-437 (9), c= 16.158 (10) A~, fl=90.83 (5) °, Z=8, T=23°C, Dx= 1.42 g.cm -a, Din= 1"37 g.cm -a. The intensities of 2234 independent reflexions were measured with a four-circle diffractometer. The structure was solved using the symbolic addition method and refined by full-matrix least-squares analysis to a weighted least-squares residue of 0.048. In both of the two independent molecules, the plane of the acyl group is rotated approximately 65 ° from the plane of the phenyl ring and both molecules have the trans conformation. The C-NOz bond lengths are similar to those in related compounds with electron donating substituents.

The structure (1) of rosein 111, indicated by chemical and spectroscopic evidence, has been confirmed by an X-ray analysis of the metabolite itself, using direct methods of phase determination. ROSEIX 111, a metabolite of Trichotheciwn yoseum, was ~~ -H c y 2 * @ b / C # * O 0 (11 0 (21 first described1 by Freeman and Morrison in 1948. We have re-isolated this compound [m.p. 221°, [a], (CHC1,)-124"] in minor amount, and on the basis of the limited evidence set out below were led to formulate it as 11-/?hydroxy rosenonolactone (1). More estensive investigations,2J also terminated by lack of material, established the part structure (2), but further suggested3 that this was incorporated in a rearranged rosane skeleton.

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and hydroxylamine-N,N-disulphonates. V. A potassium salt of hydroxylamine-N,N-disulphonic acid with a displacive superlattice structure. Can. J. Chem. 66, 655 (1988).The structure of the potassium salt of hydroxylamine-N,N-disulphonate, with the formula KsHN2S40a14.H20, has been determined by X-ray diffraction. The crystals are triclinic, a = 14.01 1 (6), b = 16.1 18(9), c = 1 1.867(6) A. a = 103.28(6), p = 106.76(3), y = 86.38(3)", PI with Z = 6. The integrated intensities of 8694 independent reflections were measured on a four-circle diffractometer, 5236 of which were used in the refinement to give a final least-squares weighted residual of 0.107 and a conventional R factor of 0.081.The structure forms a six-fold derivative lattice, which arises by small displacements (ca. 0.2 A) of the atom ositions from an average structure which is triclinic with Z = 1. This results in three very short H bonds, average length 2.46 1 , which link the three independent anion-dimers, being symmetry-free in this structure. Other bond lengths and angles in the anions are very similar to those in the Rb salt. The K' ions show 8 , 9 , and I0 coordination, in a number of different polyhedral types. The three independent water molecules are each coordinated to three totally distinct K+ ions, and are linked to the anions by weak H bonds. The structural complexity 'may be explained in terms of a Lewis acid-base "mismatch" of the cations and anions present.

The crystal structure of (NH4)3C18206 has been determined. The cell dimensions are a=12.64, b = 12.48, c= 6.08 A and the space group is Pbam. The structure is pseudo-tetragonal and is isostructural with the mixed salts NaKsCI2(S206)2 and NaK2C1S206. 971