Orthorhombic Ciystal

Orthorhombic ciystals of 6-phosphogluconate dehydrogenase. Space group C222], cell parameters a=72.7A, 6=148.2 A, c= 102.9 A, a.=fi=y=90°. Typical largest dimension lmra. Photograph kindly provided by Dr M.J. Adams and Dr D. Somers with permission. 

Badens, E., Veesler, S. Sc Boistelle, R. (1999). Ciystallization of gypsum from hemihydrate in presence of additives. Journal of Crystal Growth, 198/199, 704-709 Barton, F. M. Wilde, N. M. (1971). Dissolution rates of polyaystalline samples of gypsum and orthorhombic forms of calcium sulphate by rotating disk method. Transactions of the Faraday Society, 67, 3590-3597. 

The synthesized LDHs showed well-ciystallized hydrotalcite structure. The thermal treatment converted the precursors into mixed metal oxides (V, Mo, W, Nb). X-ray diffraction analysis indicates the formation of an orthorhombic Mo7,gVi,2Nbo28,9 and M0O3 phase, the peaks are observed at 20 = 22.1, 28.2,6.2,45.2,50.0° (3). The textnral properties of the systems depend on the eonditions of preparation of LDHs, in particular on the particle size of the sample. For example BET surfaee area increased simultaneously with the partiole size (Table 2). 

X-ray single ciystal dillraction experiments at high temperatures. According to these observations, the orthorhombic modification should be named R2(Se03)3-I, and the monoclinic one R2(Se03 >3 -II. The phase transition can be also seen by means of temperature dependent X-ray powder diffraction, and for Nd2(Se03>3 it has been monitored also by differential scanning calorimetry (DSC) measurements (see section 3.4.3). 

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