Arsenious oxide

|---- |Other names || oxidize arsenic arsénieux
oxyde (III)
sesquioxyde of arsenic |---- |----- |----- |----- | Not of boiling || 457-465°C under 1 bar |----- |----- | Steam pressure || 0,275 kPa (220 °C) |-----

In industry, the arsenious oxide (As₂O₃), or trioxyde of arsenic , or arsenous oxide called “white arsenic formerly” (or even improperly arsenic ), are used to bleach the Verre. There exists in a natural state under the name of flower of arsenic , under the aspect of an odorless white powder or transparent crystals. One also finds it in the Poison S, such as the Mort in the rats. By its outlets for trade, it represents the chemical compound most important derived from the Arsenic and proves to be the by-product the most dangerous contents in certain ores like the gold mines.

Obtaining

Combustion of arsenic in the air.

4 Aces +3 O₂ --> 2 As₂O₃

Hydrolysis of the Trichloride of mineral arsenic AsCl₃
Netting containing of arsenic like the Pyrite S. (the industrial source most important).

2 FeAsS + 5 O₂ --> Fe₂O₃ + 2 SO₂ + As₂O₃.

The arsenious oxide escapes in long pipings in the form of volatile smoke which one collects in the form of white powder. It is then purified by Sublimation

Chemical properties

The arsenious oxide is an acid Amphotère which presents néammoins a behavior of weak Acide. It dissolves instantaneously in basic medium to give ions Arsénite S: H ₂ Ace O ₃⁻.

It is soluble in soda:

As₂O₃ + 4 OH^- --> 2HAsO₃^2- + H₂O

It is much less soluble in the acids, but soluble in the Hydrochloric acid to give arsenic chloride. It reacts with agents Oxydant S like the Ozone, the Hydrogen peroxide or the nitric Acid to give pentoxide As₂O₅ arsenic. The reactions with hydrogen peroxide can be explosive. It can be also reduced out of arsenic with formation of arsine AsH₃, gas very toxic. It forms a spontaneously flammable mixture with the Chlorate of sodium.

Physical properties

They vary according to the crystalline form of the substance. The asénieux anhydride is presented under two crystalline varieties and amorphous. It is sublimated beyond 200 °C in the form of As₄O₆.

cubic form: Arsenolite, most current.
monoclinical form: Claudetite.

Uses

It is the starting point for the manufacture of Pesticides containing arsenic. (arsenite of soda, sodium arsenate, soda cacodylate).
It is at the base of certain products parapharmaceutic and veterinary containing arsenic. (Néosalvarsan).
Agent of discoloration and refining of the Glass and the enamels.
Curing agent of wood.
Preserving for the food.
Commodity for the manufacture of metal arsenic, its alloys (lead, copper, aluminum, gallium) and of the arsenite (Semiconductor S).
It is used in the treatment of the Leucémie for the refractory patients with other drugs.

Health

The arsenic trisulphide is very toxic, the amount mortal is of 0,1g. All the arsenic compounds containing of the traces of this product are also very dangerous. It is Carcinogène and easily absorptive by the digestive system; its toxic effects are well established in the event of inhalation of smoke or cutaneous contact involving of the risks of Dermatite or Hyperkératose. Its elimination is fast (lifespan: 1 to 2 days) by Méthylation in cacodylic acid via the urines. However, a certain quantity of product (30à 40%) in the event of chronic exposure), is stored by the Os, the Muscle S, the Peau, the Cheveux and the Ongle S (fabrics rich in Kératine and eliminated in the weeks or the months which follow.

The primary symptoms of acute poisoning by the arsenic ingestion are digestive problems: Vomiting S, Paralysis, abdominal pains and Diarrhea S sanguinolentes. Quantities close to the amount mortal can lead to Convulsion S, disorders Cardiovasculaire S, to the ignition of the Foie and Rein S and to disorders of the blood Coagulation.

These symptoms are followed appearance of the “lines” white characteristics ( lines of Mees ) on the nails and of the loss of hair. The lower amounts generate changes of the Pigmentation of the skin. It is known that serious cases of poisoning occurred after inhalation of arsenious oxide or by contact with the skin. The first signs show an irritation of the respiratory area or exposed skin, followed by long-term central nervous system disorders. One must avoid the contact with the eyes of solutions (even diluted) of arsenious oxide.

The chronic exposure to arsenic is a risk factor of Cancer lung noted on workmen working in Fonderie S of copper in the USA, Japan and Sweden. Indeed, the arsenious oxide is present in smoke which is formed during the heating to the air of the arseniferous Minerai S.

The absorbtion continues water containing of arsenious oxide led to cancers of the skin.

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