Hittorfs phosphorus

In addition to the P8 cuneane building block, Hittorf phosphorus contains a P9 unit which serves to cross link the long tubular strands (P8-P2-P<))x in three di-... 

White phosphorus is manufactured by reaction 14.1, and heating this allotrope in an inert atmosphere at 540K produces red phosphorus. Several crystalline forms of red phosphorus exist, and all probably possess infinite lattices. Hittorfs phosphorus (also called violet phosphorus) is a well-characterized form of the red allotrope and its complicated structure is best described in terms of interlocking... 

One of the most unexpected results obtained was for Pg, where the much-studied cubic (0 ) form corresponds to a shallow local minimum in the energy surface. Simulated annealing led, however, to the Czv structure (Fig. 4b), which is much (ca. 1.7 eV) more stable. This wedge structure, which may be viewed as a (distorted) cube with one bond rotated through 90°, is a structural unit in violet (monoclinic, Hittorf) phosphorus [48]. A second isomer of Pg ( >21, Fig. 4a) is also much more stable than the cubic form. There is a striking analogy between the structures of the Pg-isomers and those of the valence isoelectronic hydrocarbons (CH)g. The cubic form of the latter (cubane) has been prepared by Eaton and Cole [49], and can be converted catalytically to the wedge-shaped form (cuneane) [50]. 

The ions P, and Pi, exhibit a striking resemblance to structural units of Hittorfs phosphorus. ... 

Only a few compounds with Pb-P linkages are at present known. There appear to be no binary lead phosphides although Hittorfs phosphorus can be crystallised from molten lead (Chapter 4.1), and the phosphide HgPbPi4 is known (Figure 8.16). 

Analysis of the minimum interatomic distances in structures of binary phosphides (table 18) does not show any clear tendencies. The 5r p largely depends on the atomic radius of R and to a smaller degree on the phosphide composition. Hovewer, some increase of the minimum interatomic distances 5r p is observed in phosphides with higher phosphorus contents. The minimum value of the (5p p for most phosphides corresponds to the P-P distances in the phosphorus modifications, 0.221 (white phosphorus) and 0.224 (red phosphorus) with an average value of 0.2219 (Hittorf phosphorus)... 

In 1841 Jons Jakob BerzeUius (1779—1884), who introduced the term allotropy, transformed white phosphorus to red phosphorous. In 1865 Johann Wilhehn Hittorf (1824—1914) was the first to produce metalhc phosphorus. Brand, however, was given credit for the discovery of phosphorus. 

Bottom Structure of Hittorf s phosphorus consisting of the same kind of tubes, but joined to grids the tube shown in the center belongs to another grid than the remaining tubes. 

We know of only two examples of parallel 2D interpenetration involving nets other than (6,3) and (4,4). One is Hittorf s phosphorus, in which two 82-10 nets, composed entirely of phosphorus atoms, interpenetrate [15], The other example, considered in the next section, differs from all the other parallel interpenetrating cases in that the composite formed is a three-dimensional interlocked structure. 

W. Hittorf prepared metallic or violet phosphorus by heating phosphorus in contact with lead for 10 hrs. at a temp, near 500°. The phosphorus dissolves in the lead at the high temp., and on cooling separates from the lead in the form of small, dark, reddish-violet, rhombohedral crystals. The crystals can be separated from the lead by treatment with dil. nitric acid, which dissolves only the lead. The crystals are further purified by boiling them with hydrochloric acid. A. Stock and F. Gomolka recommended the following procedure ... 

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. 

A review of the alleged allotropes of phosphorus reduces their number to four, namely, the a- and/3-forms of yellow phosphorus, red or violet phosphorus, and black phosphorus. Most of the work of various investigators has been directed towards elucidating the nature of red phosphorus, and of the transformation of yellow to red phosphorus and conversely. Red phosphorus was formerly considered to be amorphous, and it was often called amorphous phosphorus. The term amorphous, however, here referred more to the general appearance of the powder rather than to its minute structure. J. W. Retgers 5 showed that the particles of ordinary red phosphorus are rhombohedral crystals, which are well developed in those of W. Hittorf s violet phosphorus. All four varieties are therefore crystalline. J. W. Terwen has reviewed this subject in a general way and M. Copisarow discussed the theory of allotropy,... 

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