Phosphorus Hittorf

Violet phosphorus (Hittorf s phosphorus) is a complex three-dimensional polymer in which each P atom has a pyramidal arrangement of three bonds linking it to neighboring P atoms to form a series of interconnected tubes, as shown in Fig. 15.3.3. These tubes lie parallel to each other, forming double layers, and in the crystal stmcture one layer has its tubes packed at right angles to those in adjacent layers. 

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-... 

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,... 

History and Preparation.—The incipient crystallisation of red phosphorus, which has been noted already, can be carried to completion by a procedure due to Hittorf,9 who dissolved red phosphorus in molten lead, and on cooling obtained yellowish-red translucent plates which had a density of 2-34 and belonged to the hexagonal system of crystals. Later investigators have obtained curved rectangular leaflets... 

It was noted by Hittorf 4 that the vapour evolved by red phosphorus at 440° C. was deposited in the yellow form. But Arctowski5 found that when red phosphorus was heated in a vacuum at 100° C. it sublimed and condensed in the same form. This phenomenon was investigated... 

Figure 12 Phosphorus units in the structures of (CuQgPu, (CuOgPu, and (CuI)2Pi4 as compared to Hittorf s phosphorus...

Figure 4 The structures of P4, white phosphorus (1) Hittorf s violet allotrope (2) Orthorhombic black allotrope (3) Rhombohedral black allotrope (4) showing the hexagonal arrangement and the distortion from planar the phosphides [Pis] (5), [P2i] (6) and...

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