Scarlet phosphorus

As stated earlier, all other forms of phosphorus can be made from white phosphorus. Thus, heating white phosphorus first at 260°C for a few hours and then at 350°C gives red phosphorus. The conversion is exothermic and can become explosive in the presence of iodine as a catalyst. When a solution of white phosphorus in carbon disulfide or phosphorus tribromide is irradiated the scarlet red variety is obtained. 

Ammonium nitrate exists in four different forms, all of which are enantiotropic the change of white phosphorus into the red (or violet) variety is monotropic. Mercuric iodide exhibits a striking example of an enantiotropic transition. Above 126.3°, it is obtained in yellow rhombic crystals while below that temperature, a scarlet tetragonal modification appears. 

Properties of Red Phosphorus.—Rod amorphous phosphorus, in the state of powder, is lustreless, and destitute of crystalline structcre. Its color varies from a scarlet to... 

Bismuth may be used in place of lead, but it dissolves only one-fifth as much phosphorus, and the crystals obtained are less pure. The metals appear to be held in solid soln. Only very minute quantities of Hittorf s phosphorus are obtained by sublimation. According to L. Troost and P. Hautefeuille, the same variety is formed when red phosphorus is heated under press, to 580°. The work of A. Pedler, J. W. Retgers, and D. L. Chapman shows that this variety differs from ordinary red phosphorus only in the size and development of the crystals. Fine-grained red phosphorus is scarlet phosphorus, while coarse-grained red phosphorus is metallic or violet phosphorus. A number of other allotropes have been reported, but many of them are the result of a misinterpretation of facts, or of an incomplete knowledge of facts. 

He found that with ordinary commercial red phosphorus with 98 per cent, phosphorus, there dissolved 0-056 and 0-108 per cent, of phosphorus in respectively 10 and 42 hrs., and with a finely-divided sample 0-092 and 0-116 percent, phosphorus in 10 and 20 hrs. respectively. R. Schenck found that 100 grms. of phosphorus tribromide dissolved 0-2601 grm. of scarlet phosphorus at 172°, and 0-3634 grm. at 184°. E. Baudrimont showed that yellow phosphorus does not attack phosphoryl bromide at the b.p. L. Rosenstein found that soln. of arsenates, and arsenic, antimony, or bismuth salts are not reduced by boiling with red phosphorus but W. Finkelstein found that a nitrobenzene soln. of arsenic trichloride is reduced by yellow phosphorus and arsenic is deposited. 0. Ruff observed that phosphorus reacts with antimony trichloride in the presence of a little aluminium chloride. F. E. Brown and J. E. Snyder observed that vanadium oxytrichloride is without action on red or white phosphorus. 

Pyrotechnic Uses.—The quantity of phosphorus consumed in the match industry exceeds by far that required for all other purposes. The total consumption exceeds 1000 tons per annum, the greater part of which is worked up for matches, hundreds of millions of which are made per annum in factories in all parts of the world. The phosphorus is now applied in the red or scarlet form or as one of the sulphides (g.w.). The materials used in friction matches have varied greatly at different periods. 

Phosphorus exhibits allotropy, and formerly was thought to exist in two forms, yellow and red. In addition, several other varieties, scarlet, violet, metallic and black phosphorus, were discovered later, some of which are perhaps not to be regarded as true allotropes. Their properties will be considered partly in the present chapter, and partly in Chapter III. 

Red Phosphorus.—The chief chemical properties of red or amorphous phosphorus were determined by the discoverer and other early investigators. As compared with white phosphorus, both red and scarlet phosphorus are relatively inert, except in respect to certain reactions which depend largely on the extent of surface exposed to aqueous reagents. 

Scarlet Phosphorus, sometimes called Sehenck s phosphorus, 6 can be prepared by boiling a 10 per cent, solution of phosphorus in phosphorus tribromide. It appears to be an intermediate form between the white and the red. The conditions of its formation and its physical properties, so far as these are known, are more fully described under Scarlet Phosphorus, p. 42. 

The solid white form really is only in a state of false equilibrium, being unstable with respect to the polymerised forms at all realisable temperatures. There are also the other forms—red, scarlet and black phosphorus—the behaviour of which under definite conditions of pressure and temperature cannot be stated with any certainty. Further, the melting-point even of the well-crystallised white phosphorus can be made fcto vary under certain conditions (see p. 15). In fact, all the condensed phases, liquid and solid, behave as mixtures rather than as single pure substances. 

It has already been shown that the transition through the various grades of red phosphorus to violet phosphorus proceeds continuously as higher temperatures and longer times of heating are progressively applied. Liquid phosphorus, when in the early stage of transformation, shows a fine scarlet colour and probably then contains the form known as scarlet phosphorus or Schenck s phosphorus, from its discoverer. 

Preparation.—Scarlet phosphorus is prepared by exposing to light a solution of phosphorus in carbon disulphide or carbon tetrachloride, or by boiling a 10 per cent, solution of phosphorus in phosphorus tribromide.2 In the latter ease the product contains considerable quantities of the solvent, in which it is slightly soluble. The solvent may, however, be removed by reducing the tribromide with mercury at a temperature over 100° C. The remaining tribromide and also the mercuric bromide may then be extracted with ether.3 The lighter coloured preparations are more reactive than the darker, on account no doubt of their finer state of division. 

It may also be noted that liquid phosphorus prepared by melting in sealed tubes under high pressures may deposit scarlet crystals. 

Scarlet phosphorus has a density of 2-0, i.e. slightly less than that of red phosphorus. It is isotropic, and in this respect resembles red phosphorus which has been prepared at comparatively low temperatures. Red phosphorus which has been prepared at higher temperatures shows distinct evidence of crystalline structure. 

Scarlet phosphorus is thus a transitional form and can be converted into the red variety by heating for some time at 300° C. in an atmosphere of carbon dioxide. 

The hydrogen of this phosphide appears to have a slight acidic character, since the phosphide dissolves in alcoholic alkalies giving deep red solutions which contain polyphosphides, similar to those which are formed by the action of alcoholic alkali on finely divided scarlet phosphorus. These compounds are easily hydrolysed by dilution, or by the addition of acids, with the precipitation of a yellow or reddish mixture of solid hydrogen phosphide and scarlet phosphorus (which possibly contains a suboxide or P4H.OH8,4). 

Light Red Amorphous Phosphorus, sometimes called scarlet phosphorus, is another allotropic form. It is prepared by dissolving yellow phosphorus in phosphorus tribromide and boiling the solution. The new modification separates out of the solution as a finely divided, amorphous powder. Like dark red phosphorus, the scarlet form is not poisonous. It is, however, more chemically reactive than the former owing to its more finely divided condition. Conversion of scarlet into dark red phosphorus may be brought about by continued... 

Scarlet phosphorus is u in compositions for parlour matches, f.r. matches requiring no ledat ignition surface. 

While it was possible to make a match that ignited by friction on any solid surface without use of white phosphorus, none could equal the ease of handling of the phosphorus match. A combination of potassium pi urn bate and red phosphorus with binder and filler called Schwie-niger Masse mixtures of a sulfophosphite with potassium chlorate scarlet phosphorus—nonpoisonous but more reactive than regular red phosphorus—and other materials appeared between 1890 and 1905 to replace white phosphorus in friction matches or strike-anywhere (SAW) matches as they are called today. The problem was finally... 

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