The crystal structures of the α and β forms of Dl-methionine have been refined by block-diagonal least-squares calculations using three-dimensional X-ray data to R=0.118 and 0.088 respectively. The structures of both the forms are essentially the same as those previously reported by Mathieson (Acta Crystallogr., 5, 332 (1952)).

Craniocaudal velocity is transmitted from cervical segment to lumbar enlargement.

X-ray methods, but none of the structures of the hydrazinium salts which are characterized by the existence of the N~H + ion has yet been examined. We have thus determined the structure of the hydrazinium chloride, N~HsC1. The crystal of hydrazinium chloride obtained from an alcoholic solution are very fine needles parallel to the c axis and somewhat hygroscopic.Useful X-ray data were obtained from oscillation and Schiebold-Sauter photographs taken with filtered Cu Ka radiation. There are sixteen formula units in the unit cell of the dimensions a = 12-491 , b = 21-854 , c = 4.41 A, and the space group is C~-Fdd. The intensities of reflexions were measured by means of a microphotometer. The x and y parameters of the atoms were determined by the Patterson and the electron-density maps projected on (001), the termination error being taken into account. The z parameters were first found by the method of trial and error, using the (hOl) data together with following special sets of relations: (644) > (424) < (264), (662) < (602) and (644) >~ (824).They were then confirmed by comparing observed and calculated F values for the (hk2) reflexions. The parameter values of the atoms thus determined are given in Table 1. The effect of thermal motion was taken into account by multiplying the calculated F values with temperature factors exp [--B (sin O/,~)2], where B = 2.13 A 2 for the (hk0) reflexions and 1.90 A ~ for the (hk2) reflexions. The value of R : XIIFoI--IFclI--XIFo

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