انت هنا الان : شبكة جامعة بابل > موقع الكلية > نظام التعليم الالكتروني > مشاهدة المحاضرة

ARSENIC OXIDES

Arsenious Oxide , As₄O₆, (also known as white arsenic or as arsenic) ,may be prepared by burning arsenic in air . It is obtained commercially by roasting metallic ores containing arsenic , and it is the source of other arsenic derivatives. It exists in three varieties of which commonest is the octahedral form, M.P. 275? . It sublimes at 125-150?,and therefore , if heated, it volatilizes without fusion.

Arsenious Oxide it reduced to arsenic when heated with charcoal and when treated with an acetified solution of stannous chloride:

As₂O₆ +12HCl +6SnCl₂= As₄ + 6SnCl₄ + 6H₂O

It is whoever oxidized to arsenic oxide or to arsenate on treatment with powerful oxidizing agents such as sodium hypochlorite, nitric acid or potassium dichromate solution.

 Arsenious Oxide is an amphoteric oxide of which the acidic properties greatly predominate. It is very slightly soluble in water, but it readily dissolves in a solution of an alkali metal carbonate, to yield an arsenite:

As₄O₆ + 6Na₂CO₃= 4Na₃AsO₃+ 6CO₂

*Arsenic Oxide, As₄O₁₀,is prepared  in hydrated form by oxidizing arsenious oxide with concentrated nitric acid:

As₄O₆ + 4HNO₃ = As₄O₁₀ + 2N₂O₃ + 2H₂O

On concentrated , the solution deposits crystals of ortharsenic acid, 3H₃AsO₄.H₂O , which on further heating above 200? lose water yield arsenic oxide:

4HAsO₄ . H₂O= As₄O₁₀ + 10H₂O

  *Arsenic Oxide is a white deliquescent solid . At a red heat it melts and decomposes, liberating oxygen:

As₄O₁₀ = As₄O+2O₂

It dissolves slowly in water to give arsenic acid, and more rapidly in alkalis to give arsenates. The arsenates are analogous to and isomophours with the phosphates . Salts of orth- pyro-, and meta-arsenic acid can be prepared . The arsenates are oxidizing agents, and they reduced to rsenites by the action of sulphur dioxide or less readily by hydrogen sulphide.

ANYIMONY OXIDES

Antimonious oxide, Sb₄O₆, exists in two forms  , the structure of the octahedral form is like that of P₄O₆ , but the structure of the orthorhombic form is more complex , and it may well correspond to the presence of the inert pair in the antimony atom.

Also Antimony formed  the oxides  Sb₂O₄ and Sb₄O₁₀.