Oxides of phosphorus, arsenic, antimony and bismuth

Each of the group 15 elements from P to Bi forms two oxides, E2O3 (or E4O6) and E2O5 (or E4O10), the latter becoming less stable as the group is descended  

Levels of [N03] in waste water are controlled by legislation, limits being recommended by the World Health Organization, the Environmental Protection Agency (in the US) and the European Community. Nitrites, because of their toxicity, must also be removed. Methods of nitrate removal include anion exchange, reverse osmosis (see Box 15.3), and denitrification. The last process is a biological one in which certain anaerobic bacteria reduce [N03] and [N02] to N2  

Many organic and inorganic compounds are oxidized by concentrated HNO3, although nitrate ion in aqueous solution is usually a very slow oxidizing agent (see above). Aqua regia contains free CI2 and ONCl and attacks Au (reaction 14.116) and Pt with the formation of chloro complexes. 

The hydrogen atom in HNO3 can be replaced by fluorine by treating dilute HNO3 or KNO3 with F2. The product, fluorine nitrate, 14.54, is an explosive gas which reacts slowly with H2O but rapidly with aqueous alkali (equation 14.117). 

Aqua regia is a mixture of concentrated nitric and hydrochloric acids. 

Concentrated HNO3 oxidizes I2, P4 and Sg to HIO3, H3PO4 and H2SO4 respectively. 

---

Chapter 14 Oxides of phosphorus, arsenic, antimony and bismuth 417... 

The oxides of nitrogen bear little resemblance to those of the other pnictides, but arsenic, antimony and bismuth form oxides with the same empirical formulae as those of phosphorus ... 

The heavier phosphorus trihaUdes (PX3, X = Cl, Br, I) are prepared by direct halogenation. The trifluoride, on the other hand, is best synthesized by treating the trichloride with an ionic fluoride such as CaF2 or ZnF2- The arsenic, antimony, and bismuth trifluorides are prepared by adding hydrogen fluoride to the oxides. (If fluorine gas is used, the pentafluorides result.) The other trihalides of arsenic and antimony can be produced by direct halogenation of either the elements or the trioxides, while the bismuth trihalides are best produced by the action of aqueous hydrohalic acids on 61203. 

Heating with the following solids, their fusions, or vapours (a) oxides, peroxides, hydroxides, nitrates, nitrites, sulphides, cyanides, hexacyano-ferrate(III), and hexacyanoferrate(II) of the alkali and alkaline-earth metals (except oxides and hydroxides of calcium and strontium) (b) molten lead, silver, copper, zinc, bismuth, tin, or gold, or mixtures which form these metals upon reduction (c) phosphorus, arsenic, antimony, or silicon, or mixtures which form these elements upon reduction, particularly phosphates, arsenates,... 

---