In the periodic table, such a chemical element as arsenic occupies a position at the metal – nonmetal interface. In its activity, it is between hydrogen and copper. The non-metallic nature is manifested in the fact that it is capable of exhibiting an oxidation state of -3 (AsH 3 - arsine). Compounds with a positive oxidation state of +3 have amphoteric properties, and with a degree of +5, its acid properties are manifested. What is arsenic oxide?
Oxides and hydroxides
The following arsenic oxides exist: As 2 O 3 and As 2 O 5 . There are also appropriate hydroxides:
- Meta-arsenic acid HAsO 2 .
- Arsenic acid H 3 AsO 3 .
- Meta-arsenic acid HAsO 3 .
- Ortho arsenic acid H 3 AsO 4 .
- Arsenic acid H 4 As 2 O 7 .
What is arsenic trioxide?
Arsenic forms two oxides, of which As 2 O 3 is called trioxide. It is a substance that is often used for treatment, but it is not a completely harmless chemical. This is an inorganic compound, which is the main source of organo-arsenic compounds (compounds containing a chemical bond with carbon) and many others. Many uses of As 2 O 3 are controversial due to the toxic nature of the element. The trade name for this compound is Trisenox.
Trioxide Overview
The chemical formula of arsenic trioxide has the following form As 2 About 3 . The molecular weight of this compound is 197.841 g / mol. There are many ways to obtain this oxide. One of them is sulphide ore roasting. The chemical reaction occurs as follows:
2As 2 O 3 + 9O 2 → 2As 2 O 3 + 6SO 2
Most oxides can be obtained as a by-product of the processing of other ores. Arsenopyrite is a common impurity in gold and copper, and it releases arsenic trioxide when heated in the presence of air. This can lead to serious poisoning.
Arsenic trioxide structure
Arsenic trioxide has the formula As 4 O 6 in the liquid and gas phases (below 800 ° C). In these phases, it is isostructural with phosphorus trioxide (P 4 O 6 ). But at temperatures above 800 ° C, As 4 O 6 is destroyed to molecular As 2 O 3 . In this phase, it is isostructural with diisotron trioxide (N 2 O 3 ). In its solid state, this compound shows polymorphic ability (the ability to exist in two or more forms of crystalline structure).
Arsenic Trioxide Properties
Some of the main properties of arsenic trioxide are as follows:
- Trioxide solutions form weak acids with water. This is due to the fact that the compound is an amphoteric oxide of arsenic.
- It is soluble in alkaline solutions and gives arsenates.
- Arsenic trioxide has high solubility in hydrochloric acid (HCl) and, finally, gives arsenic trichloride and concentrated acid.
- It gives pentoxide (As 2 O 5 ) in the presence of strong oxidizing agents such as hydrogen peroxide, ozone and nitric acid.
- It is almost insoluble in organic solvents.
- He looks like a white solid in a normal physical condition.
- It has a melting point of 312.2 ° C and a boiling point of 465 ° C.
- The density of this substance is 4.15 g / cm 3 .
The use of arsenic trioxide in medicine
This chemical belongs to the class of antitumor agents and is used in the treatment of cancer. Arsenic toxicity is well known. But arsenic trioxide is a chemotherapeutic drug and has been used to treat certain types of cancer for many years. The solution used for this treatment is called Fowler's solution. In 1878, the Boston City Hospital reported that this solution could be effective in reducing the number of white blood cells in humans.
As a result, As 2 O 3 was mainly used to treat leukemia until it was replaced by radiation therapy. But after the 1930s, he gradually regained his popularity in the treatment of leukemia, until modern chemotherapy appeared. This arsenic oxide was considered the best treatment for chronic myelogenous leukemia. Even today, this substance is used to treat a specific type of acute promyelocytic leukemia with failed retinoid or anthracycline chemotherapy. It is also used to treat chronic myeloid leukemia, multiple myeloma, acute myeloid leukemia, lymphoma, and cancer of the lymphatic system.
Trioxide use
Arsenic trioxide is widely used in the production of colorless glass. This compound is also useful in the field of electronics to create semiconductors and certain alloys. It is also used in paints. Arsenic trioxide can be an effective treatment for brain tumors.
In the past, this substance was used in dentistry, but since it is a highly toxic compound, its use by modern dentists has been discontinued. Arsenic oxide (As 2 O 3 formula) is also used as a wood preservative, but such materials are banned in many parts of the world. In combination with copper acetate, arsenic trioxide gives a bright green pigment.
Highly toxic substance
Trioxide itself has a high level of toxicity. Therefore, it is always necessary to take the necessary precautions before using it. It can be very dangerous in the following cases:
- Eating If As 2 O 3 accidentally enters the digestive tract, consult a doctor immediately. Trying to induce vomiting before seeking medical attention is not recommended. You need to remove any tight clothes, take off your tie, unfasten your collar, belt, etc.
- Skin contact. In case of contact with any surface of the body, immediately wash the affected area with plenty of water. Contaminated clothing and shoes should be removed immediately and washed before reuse. In case of serious skin contact, you should immediately seek medical attention. Washing the infected area with a disinfectant soap and using an antibacterial cream may be helpful.
- Eye contact. If As 2 O 3 comes in contact with the eyes, the first thing to do is remove any contact lenses and rinse your eyes with plenty of water for 15 minutes. It is recommended to use cold water. In parallel with this, someone should call an ambulance.
- Inhalation. People who inhaled this gas should be placed in a different place with fresh air. And also you need to immediately seek medical help. If breathing is difficult, oxygen should be given immediately. If the victim is unable to breathe on their own, artificial respiration must be done.
- This compound may have toxic effects on humans. If excessive amounts of it are ingested, arsenic trioxide can even lead to death. Safety glasses and gloves should always be used when working with As 2 O 3 . Work should always be carried out in a well-ventilated area.
Side effects
Common side effects of this substance include symptoms such as:
- poor appetite;
- vomiting
- nausea;
- abdominal pain;
- constipation;
- headache;
- fatigue;
- dizziness;
- fever;
- trouble breathing
- high white blood cell count;
- high blood sugar;
- skin rash.
Less common side effects include:
- dry mouth
- confused breathing;
- chest pain;
- low white blood cell count;
- muscle and bone pain;
- swelling of the face and eyes;
- diarrhea;
- tremor;
- low blood sugar;
- low levels of oxygen in the blood.
Rare side effects of As 2 O 3 :
- irregular heartbeat (this can even lead to death);
- weight gain;
- fainting;
- distraction;
- coma;
- swollen belly;
- darkening of the skin.
Life-threatening symptoms of exposure to arsenic trioxide are weight gain, fever, difficulty breathing, shortness of breath, chest pain, cough.
Arsenic trioxide is a highly toxic substance that can even lead to death. However, it has its usefulness in the medical field. Always take precautions.
Chemical reactions
Arsenic trioxide is an amphoteric higher arsenic oxide , and its aqueous solutions are weakly acidic. Thus, it is readily soluble in alkaline solutions to produce arsenates. It is less soluble in acids, with the exception of hydrochloric acid.
Only with strong oxidizing agents, such as ozone, hydrogen peroxide and nitric acid, arsenic penta oxide with a +5 degree of acidity As 2 O 5 is formed from it . As for oxidation resistance, arsenic trioxide is different from phosphorus trioxide, which easily burns to phosphorus pentoxide. Reduction gives elemental arsenic or arsine (AsH 3 ).
Arsenic pentoxide
The chemical formula of the pentoxide is As 2 O 5 . Its molar mass is 229.8402 g / mol. It is a white hygroscopic powder with a density of 4.32 g / cm 3 . The melting point reaches 315 ° C, at which it begins to decompose. The substance has good solubility in water and alcohol. The properties of arsenic oxide make it very toxic and dangerous to the environment. This inorganic compound, which is less common, highly toxic and, therefore, finds only limited commercial use, unlike higher arsenic oxide (formula As 2 O 3 ).
Arsenic is primarily known as poison and a carcinogen. Its trioxide is a water-soluble powder that produces a colorless, tasteless and odorless solution. It was a popular way of killing in the Middle Ages. Its use continues today, but for peaceful purposes and in small quantities.