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Pyrosulfuric Acid Formula

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What is Pyrosulfuric Acid?

Pyrosulfuric acid can be defined as a strong acid. Pyrosulfuric acid is the major component of the fuming sulfuric acid. The chemical formula of pyrosulfuric acid can be represented as H2S2O7. The alternative name by which pyrosulfuric acid is known is disulfuric acid. Pyrosulfuric acid is also sometimes known as the oleum. Oleum can be defined as the oxyacid of sulfur. Oxyacid can be defined as an acid that has oxygen and hydrogen as two main components and a third element that constitutes at least one different element. It is important to note that pyrosulfuric acid is a weaker acid than sulfuric acid. 

The Formula of Pyrosulfuric Acid

The formula for pyrosulfuric acid can be represented as H2S2O7, it can be defined as an oxyacid of sulfur. Due to this, they are alternatively named as the oleum. The oleum is the most common form in which pyrosulfuric acid is found, another name for this chemical compound is disulfuric acid. It can be attributed to the presence of two hydrogen atoms in the compound as represented in the formula of pyrosulfuric acid. The linear formula of the pyrosulfuric acid is represented as H2O7S2. Another representation of the formula of pyrosulfuric acid or disulfuric acid can be done according to the Simplified molecular-input line-entry system, which is more commonly known as the (SMILES). The formula representation according to SMILES is as follows, OS(=O)(=O)OS(=O)(=O)O. 

According to the IUPAC nomenclature, the disulfuric acid can be named as sulfo hydrogen sulfate. According to the name, another way of defining the compound is referring to the compound as an anhydride of sulfuric acid (H2SO4). It is proved that the compound can be obtained by mixing two molecules of sulfuric acid followed by dehydration. Dehydration is the removal of water molecules, in this case, only one molecule is removed.

The Structural Formula of the Acid

The structural pyrosulfuric acid formula gives us a basic understanding of the bonds involved in the formation of the chemical compound. The structural pyrosulfuric acid formula also indicates the reaction that can be performed by the compound. The structural formula of the pyrosulfuric acid can be depicted as the following:

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Preparation Method of Pyrosulfuric Acid

The disulfuric acid or pyrosulfuric acid can be prepared using the chemical compound named sulfur trioxide and sulfuric acid. The preparation involves dissolving the sulfur trioxide in concentrated sulfuric acid. The chemical reaction of the preparation can be represented as the following, the end product can be easily removed through the contact separation.

H2SO4 + SO3 → H2S2O7

Sulfuric acid + sulfur trioxide  → pyrosulfuric acid

Chemical Properties

The chemical properties of the disulfuric describe the reactivity and properties of the chemical reaction, chemical properties of the compound include the chemical formula, conjugate base, hydrogen bond donor, and hydrogen bond acceptor. Some of the chemical properties of pyrosulfuric acid is mentioned as follows:

  1. The pyrosulfuric acid formula can be represented as H2S2O7.

  2. The IUPAC name of the disulfuric acid is sulfo hydrogen sulfate.

  3. The molecular weight of the chemical compound is 178.129 g/mol.

  4. The conjugate base is the disulfate.

  5. Pyrosulfuric acid is a much weaker acid when compared to the sulfuric acid.

  6. It forms persulfates.

  7. Persulfates are the salt of the disulfuric acid, the pyro sulfates are formed as a result of the reaction between disulfuric acid and bases.

  8. The decomposition of the disulfuric acid leads to the production of sulfuric acid and water. There is an elimination of sulfur trioxide.

  9. The hydrogen donor bond number is 2.

  10. The hydrogen bond acceptor number is 7.

Physical Properties

The physical properties also influence the commercial use and reaction pattern of a chemical compound. The physical properties include parameters like, structure, melting point, boiling point, appearance. Some of the physical properties are mentioned as following,

  1. The melting point of the chemical compound is 36℃.

  2. They are generally found in a low grade purity form.

  3. They are oily, fuming, and dense.

  4. The color of the compound depends upon the grade of the purity. They are generally colorless.

  5. They can sometimes be of darkish brown appearance.

Uses of the Compound

Pyrosulfuric acid has many commercial uses. Some of the more common usages of the compound are listed below:

  1. They are used in the manufacturing process of explosives.

  2. They are used in the dye industry.

  3. They are used as a sulfating agent.

  4. They are used for the petroleum refining process.

  5. Since the transportation of sulfuric acid is very difficult due to its corrosive nature they are used as the intermediate form that can be easily transported.

Safety Hazards

Since the acid is corrosive in nature the direct contact of the acid will lead to irritation and burning sensation on the skin. The direct contact of concentrated acid will lead to severe skin burns. The fumes when inhaled causes irritation in the eyes, skin, and mucous membranes of the body. The entry of the acid into the food tract can lead to permanent tissue damage, it can also be proven fatal if ingested into high concentration.


Pyrosulfuric acid can be defined as an acid that is made from the reaction of sulfur trioxide and sulfuric acid. Pyrosulfuric acid formula can be represented as H2S2O7, the presence of the two hydrogen atoms attributes to the name called disulfuric acid. According to the IUPAC nomenclature, the compound is named as sulfo hydrogen sulfate. It can also be defined as the anhydride of sulfuric acid. The compound has important commercial applications some of which include, use of acid in petroleum refining, dye manufacture, and explosive manufacture. 

Last updated date: 27th Sep 2023
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FAQs on Pyrosulfuric Acid Formula

1. What is the Chemical Formula of Pyrosulfuric Acid?

Ans- The chemical formula of the disulfuric acid also known as pyrosulfuric acid can be represented as H2S2O7.

2. What is the Conjugate Base of the Disulfuric Acid?

Ans- The conjugate base of the acid disulfide. 

3. What are Persulfates?

Ans- Pyrosulfates are the salt of the disulfuric acid, they are prepared from the reaction between disulfuric acid and bases, they are used in labs for quantitative analytic studies.