Phosphorus Hittorfs metallic

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. 

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 ... 

J. J. Berzelius also noted the resistance the metal offers to attack by aqua regia. A. Granger observed that chromium is attacked by phosphorus at 900°. W. Hittorf found that phosphoric acid makes chromium passive. W. Rohn found that 10 per cent, phosphoric acid dissolves no chromium in 24 hrs. when cold, or in an hour when hot. He also found that 10 per cent, acetic acid dissolves 0-13 grm. per sq. dm. per 24 hrs. in the cold, and 0-03 grm. per sq. dm. per hr. when hot. 

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