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In the system Ag-In, the isothermal phase transformation at 281 "C previously assumed by Weibke and Eggers has been found not to exist. Metastability of they phase and of the indium phase is persistent at room temperature. The boundaries of the intermediate phases have been redetermined. At room temperature, the equilibrium y phase (hexagonal) exists between 71.0 and 70.3 % silver. At 325 "C and higher temperatures, the y-phase region extends to higher indium concentrations than those given by Weibke and Eggers. The order-disorder transforn~ation of the y phase, postulated by Hellner, does not appear to exist. The liquidus is found to lie approximately 8 "C higher than that determined by Weibke and Eggers.At room temperature, the E phase exists between 67.5 and 65.0% silver. At these compositions, the cubic cell edges of the E phase are o = 9.878 + 0.004 and 9.887 0.004 A, respectively. The y/(y + E) phase boundary has been redetermined and extended.A new a' phase is claimed to exist at approximately 73.8 wt. % silver. It is formed by a peritectoid phase reaction at 187". In the a' phase the silver atoms occupy the face-centered positions and the indium atoms, the corner positions of the cubic lattice. The intensities of diffraction lines were calculated using such a model and were found to be in reasonable agreement with the observed intensities of the a' phase. The cell edge of the a' phase is 4.144 + 0.004 A, at room temperature, and this is identical, within experimental error, with that of the a phase.A new phase diagram for the Ag-In system has been constructed.

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Starting with the structure of (low) albite published by Taylor, Darbyshire & Strtmz in 1934, the crystal structures of a low albite and of a high albite, both nearly pure NaA1SiaO s, have been refined by means of a series of Fo and (Fo--Fc) Fourier projections parallel to all three axes.The mean bond lengths within the four non-equivalent tetrahedra are in low albite, 1-743, 1.590, 1.636 and 1.616 /i~, and in high albite 1.653, 1-639, 1.643 and 1.647 /~, with a standard deviation 0.02 A. It is concluded that in low albite the first site Sil(0) contains nearly all the A1 and that in high albite the A1 and Si atoms are randomly distributed throughout the four tetrahedral sites. The dimorphism of soda felspar is thus due primarily to differences in the degree of A1-Si ordering.Four features of the Na atom were noted: (1) In both albites the temperature factor of this atom is much greater than that implied in the f curve of Bragg & West. (2) The temperature factor is greater in high albite than in low. (3) In low albite this atom behaves as though it had an anisotropic thermal vibration with a maximum amplitude nearly along y equivalent to an atomic separation of ~ 0-1 ~. (4) In high albite the effect is similar but much more intense, equivalent to a separation of N 0.6 /~. A possible interpretation is that the Na atom occupies at random through the structures one or other of two positions, within the same large cavity, separated by N 0.1 /~ or ---0.6 A nearly along y. On this view, when the A1-Si atoms are disordered as in high albite the cavity available for Na is effectively larger than that atom can fill, whereas when the A1-Si atoms are largely ordered, as in low albite, the cavity is small enough to nearly enclose the Na atom.On the assumption that maximum stability at room temperature corresponds to local balance of electrostatic charges throughout the structure, a detailed discussion of the two albites and of sanidine and intermediate microcline leads to a number of unexpected and important conclusions: (1) In low-temperature felspars the most stable structure is not necessarily, as is generally assumed, one in which the A1-Si atoms are completely ordered. (2) The most stable potassium felspar is not 'maximum' microcline but a monoclinic (C2/m) orthoclase with A1 partially ordered into one half of the tetrahedra. (3) Intermediate microcline has an unstable charge distribution and all microclines lie outside the normal stability range of the potassium felspars, which runs from disordered sanidine to partially ordered orthoclase. (4) Most microclines probably form as the exsolution product of an alkali felspar which cooled from fairly high temperatures and which, at those high temperatures, contained a sufficient proportion of Na to confer partial ordering and the associated triclinic symmetry on the tetrahedral framework. General introductionSodium felspar (NaA1SiaOs) may exist in one of two well established modifications. The ordinary lowtemperature form, called variously low-temperature * Progress reports...

Cyclopentadienyl(triethylphosphine)copper(1), CsHsCuP(C2Hs)3, has the cell dimensions a=8.60+ 0.02, b= 11.04+0.03, c= 7.67 + 0.02 ~ and fl= 115"3+0"05 °. The space group of the crystal is P2j/m and Z= 2. The structure was solved, using the intensities obtained from Weissenberg photographs, by three-dimensional Patterson, Fourier and least-squares methods to a final R index of 0.145 when a set of hydrogen atoms was included at chemically expected positions. The analysis revealed the presence of two enantiomers distributed apparently equally and randomly throughout the crystal. The C5H5 ring is n-bonded to the copper atom with average bond lengths of 2.24 for Cu-C and 1.38 A. for C-C. The Cu-P bond length is 2.14. The presence of a n-bonded C5H5 ring is in accord with the thermal stability of the compound. CsHsCuP(C2Hs)3 is monomeric and obeys the inert gas rule.