Liquid Phosphorus

It is probable that all forms of phosphorus can be melted to form what is approximately the same colourless liquid, of density 1.745 g/cc at 44.5°C. Liquid phosphorus can be readily supercooled to a state from which the rate of crystallisation of the white form is extremely rapid. The Raman spectra of the solid and solution states of white phosphorus resemble that of the liquid, indicating that the latter also contains tetrahedral P4 molecules. Recently, evidence for two different forms of liquid P has been obtained [28]. 

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Phosphorus pentachloride is prepared by the action of chlorine on phosphorus trichloride. To push the equilibrium over to the right, the temperature must be kept low and excess chlorine must be present. Hence the liquid phosphorus trichloride is run dropwise into a flask cooled in ice through which a steady stream of dry chlorine is passed the solid pentachloride deposits at the bottom of the flask. 

The liquid phosphorus oxychloride, b.p. 107°, is a by-product and is removed by fractional distillation under normal pressure. Unless the b.p. of the acid chloride differs very considerably (say, <] 100°) from that of the phosphorus oxychloride, the acyl halide is liable to contain traces of the latter. In such circumstances it is preferable to use thionyl chloride for the preparation of the acid chloride. 

Elements that can expand their valence shells commonly show variable covalence, the ability to form different numbers of covalent bonds. Elements that have variable covalence can form one number of bonds in some compounds and a different number in others. Phosphorus is an example. It reacts directly with a limited supply of chlorine to form the toxic, colorless liquid phosphorus trichloride ... 

Phosphorus vapor consists of tetrahedral P4 molecules, and at higher temperatures also of P2 molecules (P=Pbond length 190 pm). White phosphorus forms by condensation of the vapor it also consists of P4 molecules. Liquid phosphorus normally consists of P4 molecules, but at a pressure of 1 GPa and 100 °C polymeric liquid phosphorus is formed which is not miscible with liquid P4. 

Phosphorus pentoxide reacts with moisture in the air to form phosphoric acid. WP munitions were used by U.S. military forces and their allies to mark targets and to provide smoke screen coverage for troops and equipment in combat zones. These munitions were produced primarily by the dip-fill or wet-fill method illustrated by Figure 1. The method is called dip-fill because empty munition bodies are dipped below the molten phosphorus level in an open tank until the munitions are filled with liquid phosphorus. The method is also called wet-fill because a water overlay is maintained over the liquid phosphorus (in the fill tank) to prevent spontaneous combustion of the chemical element and because the filled munition will have a slight water overlay (up to 1/8" column height allowed). 

Later, American workers2 described the preparation of this type of compound by a method which necessitated the loss of two-thirds of the fluorine concerned in the reaction. They prepared tetramethylphosphorodiamidic fluoride (bisdimethyl-aminofluorophosphine oxide) (II) by the action of phosphorus oxyfluoride on the calculated quantity of dimethylamine. In addition, it should be emphasized that phosphorus oxyfluoride is a gas and is more difficult than the liquid phosphorus oxydichlorofluoride to manipulate. In Report no. 14 on fluoro-phosphonates to the Ministry of Supply3 it was shown that our reaction could also be applied to the preparation of tetramethyl-... 

When solid phosphorus of any form—white, red, or black— is melted, it forms the same liquid phosphorus. This liquid has a density of 1.74 g/cm and viscosity 1.69 centipoise at 50°C. Liquid phosphorus boils at 280.5°C. Upon cooling, liquid phosphorus solidifies to only white phosphorus. Liquid phosphorus and its vapors consist of tetrahedral P4 molecules. The vapors, on rapid condensation, convert to white phosphorus. 

Magnesium metal burns in air with an intense white light to form solid magnesium oxide. Red phosphorus reacts with liquid bromine to form liquid phosphorus tribromide. Purple aqueous permanganate ion, MnC>4-, reacts with aqueous Fe2+ ion to yield Fe3+ and pale pink Mn2+. Although these and many thousands of other reactions appear unrelated, all are oxidation-reduction reactions. 

The so-called liquid phosphorus reported by T. de Grotthus,2 H. Rose, J. Kallhofert, and E. J. Houston were shown by D. Gomez, and F. P. Venable and A. W. Belden to be under-cooled or surfused phosphorus. 

I. Remsen and E. H. Keiser considered that they had obtained a special allotropic form of phosphorus by suddenly cooling the vapour of phosphorus by iced-water. The product is here red phosphorus, for, as shown by A. Stock and co-workers, red phosphorus can be produced by suddenly quenching phosphorus vapour at 900 -1175. H. M. Vernon reported that rhombic phosphorus, i.e. rhombic crystals of phosphorus, can be obtained by slowly cooling liquid phosphorus. This observation, however, remains unverified ... 

D. MacCrae and C. C. van Voorhis represented their measurements between 44-1° and 150° by log, p=7-9542—2757-5Z1-1 mm. L. Troost and P. Hautefeuille measured the vap. press, of liquid yellow phosphorus between 360° and 510°, and found that above 510°, the liquid was transformed so rapidly into red phosphorus that its vap. press, could not be measured. They also measured the vap. press, of red phosphorus between 360° and 577°. E. Riecke represented their values for solid red phosphorus by log10y=—45-01-f-16-28 log10 T—832jP-1 atm. and for liquid phosphorus, log10 p=—2-450+2-064 log10 T—1530 T 1 atm. P- Jolibois also measured the vap. press, of red and yellow phosphorus. A. Smits and S. C. Bokhorst gave for solid and liquid violet phosphorus from 308-5° to the critical temp., 695° ... 

According to M. Faraday,16 liquid and solid yellow phosphorus are nonconductors of electricity G. L. Knox said that the electrical conductivity of fused phosphorus is small A. Matthiessen observed that if the conductivity of silver be 100 at 0°, then that of red and yellow phosphorus is 0 0gl23 at 20° and G. Foussereau gave 0-957 XlO-11 mho for the conductivity of solid phosphorus at 11°, and 0-641 Xl0 10 mho at 42°, while for liquid phosphorus, he obtained 0-435 X10-6 mho at 25°, and 0-289 X 10 5 mho at 100°. P. W. Bridgman found the electrical resistances, R, of black phosphorus at different temp, and press., p, in kgrms. per sq. cm., were ... 

J. L. Gay Lussac and L. J, Thenard 2 about 1808, and H. Davy about 1810, prepared liquid phosphorus trichloride, or phosphorous chloride, PC13, by the action of chlorine on phosphorus. If the phosphorus be in excess, the liquid trichloride is formed, and if the chlorine be in excess, the pentachloride is produced as indicated in connection with the la reaction tr s vive between these two elements. H. Davy said ... 

AuCl (6.28 mg, 0.027 mmol) and a (solid) phosphorus ligand (0.027 mmol) were weighed into a reaction flask in air. The flask was evacuated for several minutes and charged with argon (3x). Nitromethane (2mL) was added. Liquid phosphorus ligands (0.027 mmol) were now added (either with microliter syringes or as stock solutions in nitromethane). Yellow suspensions were obtained which became... 

The degree of supercooling to which liquid phosphorus can be subjected without solidification also depends on its previous history. If the cooling be slow, pure liquid phosphorus may be kept for days at 18° C. If the liquid be heated to 100° C. and suddenly cooled to ordinary temperatures it crystallises spontaneously in a few seconds without inoculation.1 2- 3... 

THE DENSITIES OF SOLID WHITE PHOSPHORUS AND OF LIQUID PHOSPHORUS AT THE MELTING-POINT. 

The dielectric constant of solid white phosphorus was found to be 4-1 at 20° C., and that of liquid phosphorus 8-85 at 45°.3 The electrochemical potential is said to lie between those of arsenic and tellurium.4 Phosphorus is diamagnetic.8 The magnetic susceptibility of the solid white element is about 0-9 x 10 6 mass units, that of the red variety rather less.6... 

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