A test counter with its circuit especially aimed for the detection of blow holes or cracks in metallic specimens has been constructed. This counter method has been applied to the test of a specimen of Kelmet metal and found to be more convenient and speedy in detecting, interior defects than the. usual radiographic methods. The photoelectric quantum efficiencies of a brass counter containig one part of alcohol and five parts of argon at 60mm, Hg for several wave lengths have been determined in two cases: 1) the x-ray beam passing through the gas filling only, 2) the beam passing through the gas and striking the cathode metal. The quantum efficiencies. Qp. are 1.56-1.64% for Fe-Kα, 0.63-0.85% for Cu-Kα and 0.21-0.25% for Mo-Kα in the former case and 5.9-6.0% for Fe-Kα, 2.8-3.0% for Cu-Kα and 0.45-0.49% for Mo-Kα in the latter case. The resolving time necessary for the measurement of x-rays is given in the cases of the scale-of-2 or scale-of-16 circuit, and also that for the detection of feeble x-rays. The calculation shows the number of impulses arriving randomly within intervals less than the resolving time not counted due to doubles, triples, etc.
By means of X-ray analysis, a silver bearing of unknown. origin was investigated. The method of manufacture was not determined by any metallographic means, but the X-ray analysis could show that it was an electrc-plated one. Further the temperature of annealing of that specimen was determined by the X-ray methods obtaining the following results 1) by the Lane photographic method: the upper limit of annealing temperature, 340°C; 2) by the back reflection method: the upper limit of annealing temperature, 320°C and the lower limit 300°C.
The crystal structure of scorodite was determined by means of the Laue and the rotating-crystal methods. Xyiay data obtained from oscillation photographs taken with MoKoc radiation showed the structure to be built upon a simple orthorhombic unit cell with dimensions: a=10.40kX, b=8.94kX, c=10.13kX, containing eight units of the chemical formula, FeAsO4⋅2H2O. All the atoms are in general positions of the space group D162hPbca. The values of atomic parameters were &termined by the method of trial and error. The arsenate group has the configuration of a slightly distorted tetrahedron. Each iron atom is surrounded by four oxygen atoms, each hem four different arsenate groups, and two water molecules at the corners of a distorted octahedron, the latter occupying its adjacent corners.
The crystal structure of orthorhombic anhydrous strontium formate Sr (HCOO) 2 was investigated by the method of X-ray Fourier analysis. Oscillation-rotation photographs were taken with filtered Cu-Kx radiation around each of the three principal axes, the dimensions of the unit cell and the space group. being, a=6.860 kX, b=8.730 kX, c=7.253 kX (at 20°C), D42-P212121, z=4. All the atoms are on the general positions: xyz; 1/2+x, 1/2-y, -z; 1/2-x, 1/2+y, 1/2-z; -x, -y, 1/2+z. By using the Patterson functions and the Fourier series projections of the electron density the atomic parameters were obtained, their final adjustment being made by intensity calculations: Sr OI OII OIII OIV CI CII x 0 0.145 0.384 0.268 0.130 0.245 0.132 y 0.0915 0.154 0.330 0.235 0.370 0.260. 0.303 z 0 0.358 0.350 0.828 0.057 0.420 0.906 The structure determined may be described as consisting of chains _??_ parallel to the c-axis which are bound laterally through the formate ions and the ones _??_ parallel to the a-axis, both chains forming a compact spacial network together. Two types of the linkage of the formate ions were found as shown in Fig. 3a and b. The former was found in the crystal structure of sodium formate by Zachariasen and of calcium formate by one of the authors (Nitta) and Osaki. The strontium ion is surrounded by eleven oxygen atoms, three of them being rather far apart, each oxygen atom is shared by two, three or four strontium ions, and the Pauling's rule concerning the stability of ionic crystals was found to hold in its extended form. The shape and size of formate ions were found to be; HCOO (I) 1.26±0.03 kX 1.24±0.03 kX 126°±4° HCOO (II) 1.25±0.03 kX 1.25±0.03 kX 127°±4° That the two C-O distances in each HCOO radical are practically equal suggests almost complete resonance between the two valence bond structure _??_ and _??_
It has been shown that the crystal unit of cyclohexanol has the dimensions a=8.81 kX, Z=4 and the most probable space group O5h-Fm3m, and that the molecules in the lattice have statistical orientations as in the case of cubic cyclohexane. In the present paper further analysis of the crystal structure using mainly the characteristic diffuse scattering is given. The observed diffuse scattering may be classified into two sorts, the one rather circular and the other spot-like. As a first approximation, a calculation based on free rotations of molecules about centres of mass arranged at the lattice points accounted roughly for the circular haloes. In order to explain the diffuse spots, the correlation of mutual molecular orientations due to hydrogen bonds was taken into account. The average value K'Δl, of Sl'· Sl'*, where Sl is an instantaneous structure factor for the molecule at the lattice paint Rl, , depends upon the correlation of both molecules and upon Δl=l-l'. K'Δl with large value of Δl approaches K' = _??_‹S›AV l2, the behaviour of both molecules being regarded as independent with each other. Thus the intensity of diffuse scattering may be given as the equation (5) . We may assume that among molecular interactions, association due to the hydrogen bond would be by far the most predominant so that a given molecule would necessarily be associated with one of its neighbouring molecules. The possible orientations of each molecule may roughly be classified in the twelve kinds as represented by the arrows in Fig. 1. Using the probability values w (miΔl, m') that two molecules at the origin and at Δl take m-th and m'-th orientations at the same time, the intensity distribution of diffuse scattering was calculated by equations (5), (7) and (7') . The results account qualitatively for such diffuse spots as accompanied with the net planes (111) and (200), and the ones observed at the small scattering angles. Further it was shown by equation (13) that the Fourier integral using the observed intersity of diffuse scattering of the crystals containing molecules of alike atoms as cyclohexanol or cyclohexane gave directly a sort of probability value, which means the difference between the average number in unit volume of the atoms in neighbouring molecules to be found at the end of a vector R from all the atoms of a given molecule and the one to be expected if the direct neighbours were assumed to behave like the distant molecules.
A general theory of the diffraction phenomena of X-rays by a crystal having irregularities of its atomic arrangements has been developed. First, the intensity formula was written as a sum of three terms, havingg distinct meanings : the first term represents a normal Laue pattern, the second a diffuse pattern similar to that due to a gas, and the third an anomalous Laue pattern. The third term is that which we are most interested in, and is due to the correlations between the irregularities possessed by any two lattice points. It is a function J (b) of the reciprocal lattice vector b, being given by equation (2.8) . It can be concluded that the weight of the scattering power for it is in general concentrated near the reciprocal lattice points, so that it gives a diffuse pattern lying near the normal Laue spots. Explicit calculation of J (b) was carried out for two cases: (1) the irregularities are due to lattice vibrations (obtaining Waller's formula in a more exact form) and (2) they are due to the order-disorder arrangements of the atoms in an alloy of, the type AB with the simple cubic structure. In the second case, a general formula was first set up, and then Zernike's theory of the propagation of orders was. applied to represent it in a more closed form. Some aspects of the intensity of the anomalous scattering were discussed in connection with the change of the degree of orders.
The structure of ludlamite has been determined using X-ray methods (Weissenbcrg and oscillation photographs, MoKα, λ=0.71Å) . The material used is from the Ashio mine. Tochigi pref., Japan and has the composition, Fe3 (PO4) 2⋅4H2O (analysed by H. Minato, 1948) . The unit cell has the dimensions, a=10.45Å, b=4.65Å, c=9.35Å, β=79'27, containing two molecules of Fe3 (PO4) 2⋅4H2O. The space group is C _??_2h-P21/α, the reflexions (h0l) and (0k0) being absent respectively when Ii and I are odd. In the structure, each P atom is in the middle of a more or less distorted tetrahedron formed by oxygen atoms and one Fe atom occupie the center of an octahedron formed by six oxygen atoms and the other Fe that of an octahedron formed by three oxygen atoms and three H2O molecules. An FeO6 octahedron and two PO4 tetrahedra. form a complex group holding O-O edges in common. This FeP2O10 group in turn forms a chain stretched indefinitely in the direction of the b-axis, sharing oxygen atoms with the adjoining similar groups. H2O groups occupy the interstices left vacant by these larger groups of atoms. Each oxygen atom is shared by one P and one or two Fe atoms and H2O by one or two Fe atoms.
The structure of orpiment (As2S3) has been analysed using X-ray methods (Weissenl erg and oscillation photographs, Co Ka, λ=1.79A) . The unit cell has the dimensions, a=11.46A, b=9.66A, c=4.21A, β=90°, containing four molecules of As2S3. The space groap is C52A-P21/n, with reflexions (hOl) and (OkO) being absent respectively when h+l. and k are odd. The structure is comnosed of As2S3 layers held together by the weak van der Waals force. In the layer Asa toms are surrounded by three S atoms. S atoms are always shared by two As atoms. The interatomic distances and bond angles agree with ones in other compounds containing S and As.