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    Naturevolume 115pages786787 (1925) | Download Citation

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    LONDON. Royal Society, May 7.—W. Rosenhain and Miss J. McMinn: The plastic deformation of iron and the formation of Neumann lines. Experiments have been made to ascertain the effect of variations of speed on the mode of deformation of nearly pure iron. Small rectangular prisms, having one face prepared for microscopic examination, have been compressed slowly in a testing machine and also under the blow of a falling weight. Within the range of speeds possible on the testing machine used (from 20 minutes to approximately i second) slip bands of very similar character are formed. When, however, such a specimen has been compressed by the blow of a falling weight very few slip bands are formed, but the crystals are crossed by much heavier and usually very straight black bands, which have been identified with the well-known Neumann lines. The formation of Neumann lines is probably not due to twinning; they are rather of the nature of broad slip regions, possibly formed by the close juxtaposition of a large number of slip planes. The surfaces on which slip has recently occurred are regions of weakness for further deformation by shock, although they do not appear to behave in the same way with further gradual deformation. -A. E. H. Tutton: (i) The monoclinic double sulphates containing thallium.-Thallium nickel and thallium cobalt sulphates. The two salts are Tl"Ni (SO4)2. 6H2O and Tl2Co(SO4)2. 6H2O. They show close isomorphism with salts of the series containing the alkali metals, but not "eutfopism "(progression with atomic, number). Thallium in its thallous capacity is thus capable of replacing the alkali metals in the crystals of these double salts, with only a relatively small amount of change like that produced by alkali metal interchange, but without relationship to atomic number. The two new thallium salts, in common with those previously studied and also with the simple rhombic sulphate and selenate of thallium, are distinguished by their very high (relatively to other salts of the two series) refraction and dispersion. This is probably where the more complicated nature of thallium atoms produces its effect. (2) The crystallo graphic and optical properties of iodo-succinimide. Miss Yardley's X-ray results indicated a structure corresponding with the symmetry of Class 9, the pyramidal polar class of the tetragonal system, one of the classes in which optical activity in two optical antipodes is possible. It has hitherto been assumed that iodo-succinimide is ditetragonal pyramidal (Class 13). New morphological constants were found and optical activity has been discovered, blocks about 4 mm. thick being required to exhibit it clearly. Hence, Miss Yardley's conclusion that the symmetry is that of Class 9 is in every way confirmed. -Kathleen Yardley: An X-ray examination of iodo-succinimide. The dimensions of the true unit cell are 6-29 x 6-29 x 15-55 A.U. This minimum cell contains four molecules. The X-ray measurements predict that the crystals should be optically active; Dr. Tutton has since shown that this is actually the case.-B. Lambert and S. F. Gates: An investigation of the relationships existing between hydrogen and palladium. The "ascending"pressure-concentration isothermal drawn through equilibrium points obtained after successive additions of hydrogen to palladium is not, in any sense, an equilibrium curve. The "descending "pressure-concentration iso-thermals, drawn through equilibrium points obtained after successive withdrawals of hydrogen from the system, are regular, but interruption of the smooth withdrawals of gas by occasional additions of gas, and temporary cooling, have marked effects; the "descending "isothermal cannot, then, be considered an equilibrium curve. The existence, under some conditions, of a simple compound, Pd2H, is considered not improbable.-C. G. T. Morison: The effect of light on the settling of suspensions.. Fine-grade suspensions of soil and kaolin were used in the absence and presence of light. When a suspension settles in the absence of light the settling is uniform and normal. In the presence of light it develops well-marked striations and discontinuities.-Colonel N. T. Belaiew: On the inner crystalline structure of ferrite and cementite in pearlite. Pearlite, the "pearly compound "of Sorby, is built up of grains of alternating lamellae of cementite and ferrite. The orientation of these lamellae is different in different grains. The cementite lamella shows its "petal-like "structure and seems warped and twisted. The exposed outer edge shows rectangular steps pointing to a constant linear unit. The ferrite lamella reveals, at the edge, "isolated cubes "of ferrite of about 250 MM edge. The ferrite lamella seems to be built up of a multitude of such small cubes, and both the warping of the cementite lamellae and the cracking of ferrite may be traced to the Arx point, where the expansion of volume, due to the change from the face-centred to the cube-centred lattice in iron, counteracts - in the pearlite areas - the normal contraction of the cooling specimen. Reacting to the ' ensuing stresses, the cementite lamella becomes warped and twisted, and the ferrite splits up into a multitude of blocks or cubes.

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    https://doi.org/10.1038/115786a0

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