Phosphorus transition point

There is a series of arsenatophosphates corresponding with each of the three forms of condensed potassium arsenate and phosphate, the transition points and melting point of which vary systematically with composition (see Fig. 10). A chain structure for the a-form of potassium arsenate and arsenophosphate may be inferred from their isomorphism with (KP03)xB. The 7-forms also contain high-molecular anionic chains for, when they are hydrolyzed, monoarsenate and polyphosphates with chain length up to n = 6 are formed, depending on their phosphorus content. No metaphosphate is produced, however. 

A. Smits and S. 0. Bokhorst gave 589-5° at 43-1 atm. for the triple point of violet phosphorus. D. L. Chapman, and P. Jolibois estimated the triple point to be c. 600°. W. Marckwald and K. Helmholtz found the transition point of red to black phosphorus to be 575°. P. W. Bridgman found that the transition point of cubic or a-yellow phosphorus to hexagonal or /1-yellow phosphorus to be ... 

Phosphorus crystallizes in at least five polymorphic forms. The white form is metastable and is prepared by condensing the vapour. There are apparently two closely related modifications of white P, with a transition point at —77°C. The... 

Law of Successive Reactions.— When sulphur vapour is cooled at the ordinary temperature, it first of all condenses to drops of liquid, which solidify in an amorphous form, and only after some time undergo crystallisation or when phosphorus vapour is condensed, white phosphorus is first formed, and not the more stable form, violet phosphorus. It has also been observed that even at the ordinary temperature (therefore much below the transition point) sulphur may crystallise out from solution in benzene, alcohol, carbon disulphide, and other solvents, in the monoclinic form, the less stable crystals then undergoing transformation into the rhombic form a similar behaviour... 

Besides the ordinary white phosphorus which crystallises in the regular system, Bridgman has discovered the existence of a second form of white phosphorus, possibly belonging to the hexagonal system. These two forms of white phosphorus are enantiotropic, with a transition point at — 76 9° under atmospheric pressure. 

As has already been stated, two forms of white phosphorus are known which show a transition point under atmospheric pressure at — 76 9°. This is represented by the point B in the equilibrium diagram. This transition point is raised by pressure, as is shown by the following data determined by Bridgman —... 

In the case of phosphorus, therefore, it is more than possible that we are dealing, not simply with two polymorphic forms of the same substance, but with polymeric forms, and that there is no transition point at temperatures above the absolute zero, unless we assume the molecular complexity of the two forms to become the same. The curve for violet phosphorus would therefore lie below that of white phosphorus, for the vapour pressure of the polymeric form, if produced from the simpler form with evolution of heat, must be lower than that of the latter. As the vapour-pressure curve of molten white phosphorus is continuous with that of molten violet phosphorus, we must assume that in molten phosphorus wc have an equilibrium between associated and non-associated molecules varying with the temperature. ... 

A. Water. Other systems of the substance water. B, Sulphur. Metastable systems. Bivariant systems. C. Tin. Transition point. D. Phosphorus, E. Liquid Crystals or Anisotropic Liquids. Nature of liquid cryst s. Equilibrium relations in the case of liquid crystals. 

In 1953, Corbridge and Lowe confirmed that at normal temperatures white phosphorus is cubic with a = 18.51 A, and has a density of 1.83 g/cc (a form). It appears as glistening colourless polyhe-dra of various kinds if grown by slow sublimation in sealed tubes [26]. At -77°C the cubic form transforms to a hexagonal (later reported as triclinic) p form with a density of 1.88 g/cc. The transition point is raised to 64°C under a pressure of 11,600 atmospheres. The existence of a metastable low-temperature (monoclinic) y form, with density 1.94 g/cc, has also been claimed as well as other high-pressure forms [27,27a,28,29]. It appears not unlikely that quite a number of white varieties, each built from discrete P4 units, may be capable of existence. 

This discussion will deal mainly with phosphorus heterocycles, but the points will generally be applicable to the emerging chemistry of the lower group members (As, Sb and Bi). Phosphorus heterocycles such as phosphabenzene or the phospholes can form bonds with transition metals in a variety of modes. Because the chemistry of the phospholes is more fully developed, this series will be used to exemplify the area generally. Phospholes are readily synthesized in a one pot process (equation 69).270 The yield is variable depending on the nature of X and the nitrogen base used, but typically is between 60 and 85%. 

R. Lorenz and W. Herz studied some relations of the transition temp. A. Smits and S. C. Bokhorst gave 690-9° for the sublimation point of violet phosphorus. 

The photochemistry of transition carbonyl complexes of chromium or iron with phosphirane or l//-phosphirene ligands is studied with time-dependent DFT theory to explore the propensity of the excited metal-phosphine-carbonyl complexes to expel their ligands <2003JA3558>. The complexes of these phosphorus heterocycles show similar behavior as carbonyl complexes with the PH3 ligand and they differ mainly in their enhanced a-donating ability. The calculations point that the excited complexes prefer the expulsion of the phosphorus substituents, which can be an alternative method to demetalate transition metal complexes of organophosphorus compounds. 

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