Triclinic crystal

Sodium metaniob ate (1 1) [67211-31-8] Na20 Nb20 7H20 or Na2Nb20g-7H20, separates as colorless triclinic crystals as a result of concentrating the mother Hquor from the preparation of the 7 6 sodium niobate by spontaneous evaporation. It also can be obtained by fusion of the anhydrous pentoxide in sodium hydroxide or carbonate. 

Properties of PET Molding Resins. The fliU crystal stmcture of poly(ethylene terephthalate) has been estabhshed by x-ray diffraction (134—137). It forms triclinic crystals with one polymer chain per unit cell. The original cell parameters were estabhshed in 1954 (134) and numerous groups have re-examined it over the years. Cell parameters are a = 0.444 nm, b = 0.591 nm, and c = 1.067 nm a = 100°, (3 = 117°, and 7 = 112° and density = 1.52 g/cm. One difficulty is determining when crystallinity is fliUy developed. PET has been aimealed at up to 290°C for 2 years (137). 

The most common form of calcium thiosulfate is the hexahydrate [10035-02-6] CaS202 6H20, which has triclinic crystals and a density of 1.872 g/cm at 16°C (84). Heating, however, does not give the anhydrous salt because of decomposition at 80°C. At lower temperatures, dehydration stops at the monohydrate [15091-91-5]. The solubiUty of calcium thiosulfates in water is as follows ... 

Ramsay 1 has isolated a crystalline sesquiterpene alcohol from the essential oil distilled from the bark of the juniper tree. It forms optically inactive triclinic crystals, melting at 107°, and having the formula CjjH O. 

Znj(P04)2 4H2 0 appears in three crystal forms, a-hopeite (rhombic plates), 3-hopeite (rhombic crystals), and p-hopeite (triclinic crystals). Their transition points are at 105, 140 and 163°C respectively. It has been observed that zinc phosphate coatings heated in the absence of air lose their corrosion resistance at between 150 and 163°C. 

PET crystallizes in a triclinic crystal structure with unit cell dimensions as follows [44] ... 

To model the monoclinic crystal, deform the model from step 5 along one axis. To model the triclinic crystal, deform the model from step 5 until it has no 90° angles. 

Symmetry restrictions exist for tensors describing macroscopic physical properties of all but triclinic crystals, and for tensors describing the local properties of atoms at sites with point-group symmetries higher than I. 

Lustrous triclinic crystals acid taste hygroscopic density 2.83 g/cm decomposes at 75°C reacts slowly with water soluble in acids and acetone insoluble in alcohol... 

Colorless, transparent triclinic crystal or white granule or powder density 1.435 g/cm3 melts at 171°C under normal heating however, slow heating causes loss of water sparingly soluble in cold water (4.7% at 20°C) pH of 0. IM solution 5.1 readily dissolves in hot water (19.1% at 80°C and 27.5% at 100°C) also soluble in lower alcohols and moderately soluble in pyridine. 

Copper(II) oxide is found in nature as the minerals tenorite and paramela-conite. They differ in crystalline structure tenorite exists as triclinic crystals while paramelaconite consists of tetrahedral cubic crystals. 

Orange yellow triclinic crystals or fluffy powder hygroscopic density 3.111 g/cm3 at 15°C sublimes at 64°C with decomposition melts at 101°C at 16 atm hydrolyzes in water soluble in ethanol, carbon tetrachloride and benzene soluble in concentrated hydrochloric acid but hydrolyzes in dilute acid. 

The anhydrous chloride is a white hexagonal crystal hygroscopic density 3.84 g/cm3 melts at 850°C soluble in water. The heptahydrate is a white triclinic crystal decomposes at 91°C soluble in water and ethanol. 

Wollastonite is calciiun sihcate with a triclinic crystal system (P21). It has infinite-chain structure, with three tetrahedra per unit cell arranged parallel to y, this repeat unit consists of a pair of tetrahedra joined apex to apex as in the [Si07] group, alternating with a single tetrahedron with one edge parallel to the chain direction. Steady-state luminescence of wollastonite has been previously studied and luminescence of Mn, Fe and supposedly Cr has been proposed (Min ko et al. 1978). 

The compound K4 75 [Pt(CN)4] 1.5H20 forms bronze-colored triclinic crystals... 

The crystal descriptions become increasingly more complex as we move to the monoclinic system. Here all lattice parameters are different, and only two of the interaxial angles are orthogonal. The third angle is not 90°. There are two types of monoclinic space lattices simple monoclinic and base-centered monoclinic. The triclinic crystal, of which there is only one type, has three different lattice parameters, and none of its interaxial angles are orthogonal, though they are all equal. 

Potassium Pentachloro - ammino - platinate, [Pt(NH3)Cl5] K.H20, is produced by treating potassium trichloro-ammino-platinite, [Pt(NH3)Cl3]K, with chlorine. It separates in yellowish triclinic crystals. 

The periodates 0 the alkaline earths.—C. F. Rammelsberg13 obtained calcium metaperiodate, Ca(I04)2, by the action of periodic acid on a soln. of calcium hydroxide or dimesoperiodate, the solid separates on concentrating the acid soln. similarly, when a soln. of strontium carbonate in an excess of periodic acid is cone, in a desiccator, large, probably triclinic, crystals of hexahydrated strontium metaperiodate, Sr(I04)2.6H2O, are formed. They lose 12-36 per cent, of water when cone, over cone, sulphuric acid, and the remainder at 100°. This salt explodes when heated the aq. soln. has an acid reaction, and gives a precipitate when treated with ammonia. When the attempt is made to concentrate the soln. of barium metaperiodate, Ba(I04)2, prepared in a similar manner, the dimesoperiodate is deposited when the soln. is cone., so that the metaperiodate has not been isolated in a solid state. 

The lattice points of a triclinic crystal may be joined in various ways to form differently shaped unit cells (see p. 151). It is usually most convenient to use the cell with the shortest edges, unless there is some special feature which recommends some other direction as a unit cell edge. Donnay (1943) recommends that the shortest axis shall be called c and the longest b and that the angles a and ft shall be obtuse. 

Monoclinic and triclinic crystals, The indicatrix for monoelinie and triclinic crystals is of the same type as that for orthorhombic... 

In triclinic crystals there are no restrictions at all on the position of the indicatrix with respect to the crystal axes. No axis of the ellipsoid need coincide with any one of the crystal axes. Consequently the position of the ellipsoid may vary with the light w avelength for all crystal orientations incomplete extinction with abnormal interference colours at the position of minimum illumination may therefore be seen for any crystal orientation. 

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