The sulfurous acid is a mineral that comes from sulfur oxide when water is added. Its formula and chemical structure, as well as the uses according to the safety data sheet, are indicated for several purposes, so it is important to know its properties and characteristics to use it correctly.
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What is sulfurous acid
It is a mineral acid produced from sulfur. Known as sulfur trioxide acid IV, it has the chemical structure Na2SO3 + 2 HCl → H2SO3 + 2 NaCl, and its molecular weight is 82.07 g/mol.
It is considered a reducing agent, transferring electrons to an oxidizing agent. Through a chemical reaction called “reduction-oxidation,” sulfurous acid donates some of its electrons. These electrons move from one agent to another (from the reducing agent to the oxidizing agent).
Its form of presentation, how it is available for sale, is in the form of a colorless liquid that has a strong odor reminiscent of sulfur.
Formula and chemical properties
- Semideveloped formula: H2SO3.
- Density: 1030 kg/m3 or 1.03 g/cm3.
- Molar mass: 82.07 g/mol.
- CAS number: 7782-992.
- Liquefaction: -10°C.
- Freezing: -76°C.
- Color: colorless.
- Odor: pungent.
It is a very unstable substance due to the properties of sulfurous acid. It is only available for sale in solution form. This can be done with water or alcohol.
A characteristic of this acid is that it is highly corrosive, so it is used as a powerful reducing agent.
Uses of sulfurous acid
- Chemical products manufacturing.
- Pharmaceutical production.
- For the paper industry.
- Refining petroleum and producing derivatives.
- Disinfectant.
- As a rodenticide.
- Bleaching agent.
It is well known in various industries, including chemical, cosmetic, and paper or petroleum industries. In the chemical industry, it is added to create a series of compounds and materials used to produce consumer products.
Sulfurous acid in cosmetics and medicine is used as a base for making drugs and skin care creams.
It is also used in paper manufacturing because it works as a bleaching agent. This last property of sulfurous acid is used to remove chlorine stains.
The extraction of sulfurous acid can be natural or mechanical, meaning it appears in nature when sulfur oxide is washed by rain, a process that leads to what is known as acid rain or it can be triggered in a laboratory. In the latter, a hydrochloric acid dilution and sodium sulfite in water are prepared.
The uses of sulfurous acid as a disinfectant are for small or medium-sized businesses or establishments. Its properties in this area are limited, but they can serve as a measure to sanitize spaces.
In the past, it was also used as a rodenticide to eliminate rat pests, although over time it was found that cyanide acid and similar derivatives were more effective.
Uses in medicine
In clinical settings, it is also present since sulfurous acid serves as an antiseptic and anti-putrefactive agent, meaning it works as an agent to eliminate microbes from living tissues. It is also effective in preventing skin infections, similar to the uses of hydrogen peroxide and iodine.
Sulfurous acid in medicine can be applied to prevent the decay of meat and parts of the body. It is anti-putrefactive.
Nomenclature
There are several definitions and names by which this mineral compound can be accessed. The nomenclature of sulfurous acid is:
- Systematic nomenclature: Hydrogen trioxosulfate IV.
- Stock: Sulfuric acid trioxide IV.
- Traditional nomenclature: Sulfuric acid trioxide IV.
It belongs to the group of oxoacids, which are ternary combinations that consist of hydrogen + a non-metal element + oxygen. In this respect, oxoacids can also be produced with some metals such as manganese, chromium, vanadium, or tungsten, as these, in a high oxidation state, act as non-metals. Another ternary element and oxoacid is phosphoric acid, which serves as a weak acid due to its formulation, similar to sulfurous acid.
Relationship with sulfur dioxide
In nature, it is present through the chemical reaction produced by sulfur dioxide (SO2) and water from the atmosphere. This leads to an environmental process called acid rain.
Its presence in the environment is mostly due to the large emission of sulfur from factories.
Differences between sulfuric and sulfurous acid
Although the name can cause confusion, these are actually two different acids. The pH of sulfuric acid is 0, while that of sulfurous acid ranges from 2.8 to 4. On the other hand, anhydrous sulfurous acid contains no water, as anhydrous substances are generally categorized as water-free.
Additionally, sulfurous acid has a valence of 4, while sulfuric acid has a valence of 6. The former is a weak acid, and the latter, sulfuric acid, is a strong acid in its first dissociation, when it loses hydrogen. Unlike hydrogen trioxosulfate IV or sulfurous acid, which is always weak.
- Sulfur dioxide II, IV, VI.
- Sulfuric acid.
- Peroxosulfuric acid.
- Peroxodisulfuric acid.
- Sulfur.