Expansion under compression: The unit‐cell volume of graphite oxide pressurized in water media, continuously increases reaching a sharp maximum at ca. 1.3–1.5 GPa (see picture, squares). Expansion of the lattice to a maximum of about 28–30 % is because of gradual pressure‐induced water insertion into the interlayer space of graphite oxide. The effect is reversible (triangles), resulting in a unique “breathing” of the structure upon pressure variation.

The effect of pressure on L-alanine has been studied by X-ray powder diffraction (up to 12.3 GPa), single-crystal X-ray diffraction, Raman spectroscopy and optical microscopy (up to approximately 6 GPa). No structural phase transitions have been observed. At approximately 2 GPa the cell parameters a and b become accidentally equal to each other, but without a change in space-group symmetry. Neither of two transitions reported by others (to a tetragonal phase at approximately 2 GPa and to a monoclinic phase at approximately 9 GPa) was observed. The changes in cell parameters were continuous up to the highest measured pressures and the cells remained orthorhombic. Some important changes in the intermolecular interactions occur, which also manifest themselves in the Raman spectra. Two new orthorhombic phases could be crystallized from a MeOH/EtOH/H(2)O pressure-transmitting mixture in the pressure range 0.8-4.7 GPa, but only if the sample was kept at these pressures for at least 1-2 d. The new phases converted back to L-alanine on decompression. Judging from the Raman spectra and cell parameters, the new phases are most probably not L-alanine but its solvates.

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Ausdehnung unter Druck: Das Elementarzellvolumen von Graphitoxid erhöht sich in wässrigem Medium unter Druck kontinuierlich, bis es bei 1.3–1.5 GPa ein scharfes Maximum erreicht (siehe Bild, Quadrate). Die Gitterexpansion um maximal 28–30 % beruht auf der graduierlichen Einlagerung von Wasser zwischen den Graphitoxidschichten. Der Effekt ist reversibel (Dreiecke), sodass die Struktur bei der Druckvariation „atmet“.

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Raman spectra of the internal vibrations of tetrahydrofuran molecules in two gas hydrate phases formed in the tetrahydrofuran-water system, as well as the spectra of solid and liquid tetrahydrofuran, under highpressure conditions have been studied for the first time. A conclusion that the high-pressure hydrate is, most probably, of clathrate nature is made on the basis of spectral data. This hydrate is stable in the pressure range 0.49-3 GPa at room temperature. At a pressure of 3 GPa, the upper boundary (with respect to pressure) of the existence of the high-pressure hydrate is discovered. It corresponds to the decomposition of the hydrate into solid tetrahydrofuran and ice VII.

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