Arsenic halides simple

Arsenic Halides. Arsenic forms a complete series of trihaUdes, but arsenic pentafluoride is the only well-known simple pentahaUde. AH of the arsenic haUdes, the physical properties of which are given in Table 2, are covalent compounds that hydrolyze in the presence of water. The trihaUdes form pyramidal molecules similar to the trivalent phosphoms analogues and may be prepared by direct combination of the elements. 

Class I. ELEMENTS. A. Metals. Cubic copper, silver, gold, iron, platinum, iridium. - Tetragonal tin. - Rhombohedral and Hexagonal arsenic, antimony, bismuth, tellurium, (Os, Ir). - B. Metalloids. Cubic diamond. - Hexagonal graphite. - Orthorhombic sulfur, iodine. - Monoclinic sulfur, selenium. - Class II. SULFIDES. - Class HI. HALIDES. -Class IV. OXIDES, divided into SIMPLE OXIDES and COMPLEX OXIDES, such as CARBONATES, PHOSPHATES, SILICATES, BORATES and SULFATES. 

There are no arsenic or antimony analogues of the simple ammonium or phos-phonium halides. (Of the latter, PH4CI, PH4Br, and PH4I are known, the latter forming brilliant cubes which can be sublimed like an ammonium salt.) The tetrahedral configuration of substituted arsonium ions has been demonstrated in crystalline [As(CH3)4]Br and [As(C6Hs)4]I3. 

This article is concerned mainly with the simple halides of phosphorus, arsenic, antimony, and bismuth compounds that also contain other elements or groups will be considered only to a limited extent. Nitrogen compounds show special features associated with the absence in nitrogen of d electrons for bonding, and are not easily discussed together with compounds of the heavier elements they will therefore be omitted. Bismuth has metallic properties that differentiate its compounds from those of elements in the middle of the group the break in properties between the compounds of antimony and bismuth is not, however, so marked as that between compounds of nitrogen and phosphorus. 

Purification through sublimation is applicable to a number of organic and inorganic substances and is useful for the purification of many simple inorganic compounds used as working standards in analysis, including ammonium halides, arsenic(III) oxide, phosphorus(V) oxide, and iodine. 

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