In the periodic table, such a chemical element as arsenic occupies a position on the metal-nonmetal border. In its activity, it is between hydrogen and copper. The non-metallic character is manifested in the fact that it is able to exhibit an oxidation state of -3 (AsH3 - arsine). Compounds with a positive oxidation state of +3 have amphoteric properties, and with a degree of +5 its acidic properties are manifested. What is arsenic oxide?
Oxides and hydroxides
The following arsenic oxides exist: As2O3 and As2O 5. There are also corresponding hydroxides:
- Meta-arsenous acid HAsO2.
- Orthoarsenic acid H3AsO3.
- Meta-arsenic acid HAsO3.
- Orthoarsenic acid H3AsO4.
- Pyromarsenic acidH4As2O7.
What is arsenic trioxide?
Arsenic forms two oxides, of which As2O3 has the name trioxide. It is a substance that is often used for medical purposes, but it is not exactly a harmless chemical. It is an inorganic compound that is the main source of organoarsenic compounds (compounds containing a chemical bond with carbon) and many others. Many uses of As2O3 are controversial due to the element's toxic nature. The trade name for this compound is Trisenox.
General information about trioxide
The chemical formula of arsenic trioxide is As2O3. The molecular weight of this compound is 197.841 g/mol. There are many ways to obtain this oxide. One of them is the roasting of sulfide ore. The chemical reaction proceeds as follows:
2As2O3 + 9O2 → 2As2 O3 + 6SO2
Most oxides can be obtained as a by-product of processing 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.
Structure of arsenic trioxide
Arsenic trioxide has the formula As4O6 in liquid and gasphases (below 800°C). In these phases, it is isostructural with phosphorus trioxide (P4O6). But at temperatures above 800°C, As4O6 breaks down to molecular As2O 3. In this phase, it is isostructural with diisotron trioxide (N2O3). In its solid state, this compound exhibits polymorphic capability (the ability to exist in two or more forms of crystal structure).
Properties of arsenic trioxide
Some of the main properties of arsenic trioxide are as follows:
- Solutions of trioxide form weak acids with water. This is because the compound is amphoteric arsenic oxide.
- It is soluble in alkaline solutions and gives arsenates.
- Arsenic trioxide has a high solubility in hydrochloric acid (HCl) and finally gives arsenic trichloride and concentrated acid.
- It produces pentoxide (As2O5) in the presence of strong oxidants such as hydrogen peroxide, ozone and nitric acid.
- It is almost insoluble in organic solvents.
- He looks like a white solid in his normal physical state.
- 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/cm3.
Use of arsenic trioxide in medicine
This chemical belongs to the class of anticancer drugs and is used in the treatment of cancer. Toxicityarsenic is well known. But arsenic trioxide is a chemotherapy drug and has been used to treat certain types of cancer for years. The solution used for this processing is called Fowler's solution. In 1878, the Boston City Hospital reported that this solution could be effective in reducing a person's white blood cell count.
As a result As2O3 was mainly used to treat leukemia until radiation therapy replaced it. But after the 1930s, it slowly regained its popularity in the treatment of leukemia, until the advent of modern chemotherapy. 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 after failed retinoid or anthracycline chemotherapy. It is also used to treat chronic myeloid leukemia, multiple myeloma, acute myeloid leukemia, lymphoma, cancer of the lymphatic system.
Using Trioxide
Arsenic trioxide is widely used in the production of colorless glass. This compound is also useful in the field of electronics for making semiconductors and some alloys. It is also used in paints. Arsenic trioxide may 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 modernstopped by dentists. Arsenic oxide (formula As2O3) is also used as a wood preservative, but such materials are banned in many parts of the world. Combined with copper acetate, arsenic trioxide produces a vibrant green pigment.
Highly toxic substance
The 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 As2O3 is accidentally ingested, seek immediate medical attention. It is not recommended to try to induce vomiting before seeking medical attention. Remove any tight clothing, remove tie, unbutton collar, belt, etc.
- Skin contact. In case of contact with any surface of the body, immediately rinse the affected area with plenty of water. Contaminated clothing and footwear should be removed immediately and washed before reuse. In case of serious skin contact, you should seek immediate medical attention. Washing the infected area with disinfectant soap and applying an antibacterial cream may be helpful.
- Eye contact. If As2O3 comes into contact with the eyes, the first thing to do is to remove any contact lenses and rinse the eyes with plenty of water for 15 minutes. It is recommended to use cold water. In parallel with this, someone must callambulance.
- Inhalation. People who have inhaled this gas should be placed elsewhere with fresh air. You should also seek immediate medical attention. If breathing is difficult, oxygen should be administered immediately. If the casu alty is unable to breathe on his own, artificial respiration should be given.
- This compound can be toxic to humans. If an excessive amount of arsenic trioxide enters the body, it can even lead to death. Safety glasses and gloves should always be used while working with As2O3. Work should always be done in a well-ventilated area.
Side effects
Common side effects of this substance include symptoms such as:
- poor appetite;
- vomit;
- nausea;
- abdominal pain;
- constipation;
- headache;
- fatigue;
- dizziness;
- fever;
- breathing problems;
- high white blood cell count;
- high blood sugar;
- skin rash.
Less common side effects include:
- dry mouth;
- bad breath;
- chest pain;
- low white blood cell count;
- muscle and bone pain;
- swelling of the face and eyes;
- diarrhea;
- tremor;
- low blood sugar;
- low blood oxygen levels.
Rareside effects As2O3:
- irregular heartbeat (it can even lead to death);
- weight gain;
- fainting;
- absent-mindedness;
- coma;
- swollen belly;
- darkening of the skin.
Life-threatening symptoms of arsenic trioxide exposure 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 utility in the medical field. Precautions must always be taken.
Chemical reactions
Arsenic trioxide is an amphoteric higher oxide of arsenic, and its aqueous solutions are slightly acidic. Thus, it readily dissolves in alkaline solutions to produce arsenates. It is less soluble in acids except hydrochloric acid.
Only with strong oxidizing agents such as ozone, hydrogen peroxide and nitric acid, it forms arsenic penta-oxide with +5 acidity As2O 5. In terms of oxidation stability, arsenic trioxide is different from phosphorus trioxide, which easily combusts to phosphorus pentoxide. Reduction gives elemental arsenic or arsine (AsH3).
Arsenic pentoxide
The chemical formula of pentoxide is As2O5. Its molar mass is 229.8402 g/mol. It is a white hygroscopic powder with a density of 4,32g/cm3. 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 highly toxic and dangerous to the environment. It is an inorganic compound that is less common, highly toxic and therefore has only limited commercial use, unlike the higher arsenic oxide (formula As2O3).
Arsenic is known primarily as a poison and a carcinogen. Its trioxide is a water-soluble powder that produces a colorless, tasteless and odorless solution. It was a popular method of killing during the Middle Ages. Its use continues today, but for peaceful purposes and in small quantities.
