Crystal trigonal .

Anhydrous aluminum bromide, AIBr., forms colorless trigonal crystals and exists in dimeric form, in the crystal and Hquid phases (1). Dissociation... 

KNO3 128 200 Endotherm - rhombic - trigonal crystal transition. 

White trigonal crystals hygroscopic refractive index 1.735 density 2.38 g/cm melts to a clear melt at 264°C decomposes at 600°C highly soluble in water (90g/100g at 28° C solubility greatly increases with temperature (234g/100g at 100°C) also, soluble in methanol, pyridine and ammonia solution. 

The anhydrous salt consists of white trigonal crystals refractive index 1.717 density 2.958 g/cm decomposes at 350°C practically insoluble in water (106 mg/L at room temperature) Ksp 1.0x10- low to moderate solubility under partial pressure of CO2 (3.5 and 5.9 g MgCOs/lOOg saturated solution at CO2 pressure 2 and 10 atm, respectively) insoluble in acetone and ammonia dissolves in acids. 

Colorless trigonal crystals or fine white crystals or granules density 3.27 g/cm3 at 18°C melts at 350°C decomposes at about 370°C evolving oxygen moderately soluble in water, 13.3 g/lOOmL at 40°C slightly soluble in alcohol insoluble in acetone. 

The dihydrate exists as transparent leaflets refractive index 1.594 density 2.672 g/cm3 at 25°C. The hexahydrate is colorless trigonal crystals or white granules refractive index 1.536 density 1.93 g/cm effloresces in air melts at... 

If silver nitrate be treated with a soln. of sodium dimesoperiodate in dil. nitric acid, and the pale greenish-yellow precipitate be washed with water acidified with nitric acid, and then dissolved in warm dil. nitric acid, the soln. furnishes, on cooling, straw-yellow trigonal crystals of trihydrated silver dimesoperiodate, Ag4I209.3H20. The same salt is formed when the orange-red crystals of silver metaperiodate ate digested with water and a soln. of potassium dimesoperiodate, acidified with nitric acid. 

It is often more convenient to refer some trigonal crystals to a rhombo-hedral oell which has three equal axes making equal angles not 90° with each other. The three equal rhombohedral axes are equally inclined to the c axis of the hexagonal-type cell. 

When we are looking along the unique axis, both indices of the crystal or fragment are equal to 1 525 the crystal will therefore not show any interference colours when examined between crossed polarizers it will appear to be isotropic. This direction of apparent isotropy is called the optic axis there is only one such direction in the crystals we have hitherto dealt with—tetragonal, hexagonal, and trigonal crystals —and such crystals are therefore described as optically uniaxial. The optic axis necessarily coincides with the principal S3>mmetr3T axis. ... 

For cubic, tetragonal, hexagonal, and trigonal crystals, powder photographs alone may beuised. The same method may be used for crystals of orthorhombic or even lower symmetry, provided that the indices of the reflections at large angles can be found. 

Hexagonal and trigonal crystals. A% chart for these crystals can be constructed by plotting values of og(h2J -hk- -k2) along MA and values of log l2 along NC, and joining them by logarithmic curves. The axial ratio... 

Certain trigonal crystals may also be referred to rhombohedral axes, the unit cell beaig a rhombohedron defined by cell edge a and irteraxial angle a (j 90°)... 

On a theoretical basis, Pd(III) and Pd(I) ions are probably located in a distorted octahedral or trigonal crystal field (Si or Si/, Sir sites) rather than in a square planar environment. The ESR spectra of adsorbed CO CO /... 

Nbo5J Cs2, is prepared similarly to the corresponding potassium salt see below). It forms trigonal crystals. 

Rubidium and caesium salts of composition 3RbC1.2AsCl3 and 8CsC1.2AsCl3 have been obtained in the form of trigonal crystals by mixing saturated solutions of the alkali chloride and of arsenious oxide in 20 per cent, hydrochloric acid and then adding concentrated hydrochloric acid.12... 

In equation (4) A is the parameter of the trigonal crystal field. This crystal field splits the 7 2-state into an orbital singlet and a doublet, the parameter A is defined in such a way that for positive A the ground state is the orbital singlet. 

Finally, for the matrix elements of the trigonal crystal held operators we find ... 

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