Sulfuric Acid

OVERVIEW

Sulfuric acid (sul-FUR-ik AS-id) is a colorless to dark brown, dense, oily liquid that mixes completely with water. Its color depends on its purity, with compounds of sulfur adding a darker color to the colorless pure product. Sulfuric acid is also available in a form known as fuming sulfuric acid, a solution of sulfur trioxide in sulfuric acid with the chemical formula xH₂SO₄·ySO₃. Sulfuric acid is the most commonly manufactured chemical in the world. In 2004, the chemical industry produced 37,515,000 metric tons (41,266,000 short tons), of which more than half was used in the manufacture of fertilizers.

KEY FACTS

OTHER NAMES:

Hydrogen sulfate; oil of vitriol

FORMULA:

H₂SO₄

ELEMENTS:

Hydrogen, sulfur, oxygen

COMPOUND TYPE:

Acid (inorganic)

STATE:

Liquid

MOLECULAR WEIGHT:

98.08 g/mol

MELTING POINT:

10.31°C (50.56°F)

BOILING POINT:

337°C (639°F)

SOLUBILITY:

Completely miscible with water

Some historians credit the discovery of sulfuric acid to the Islamic scientist Mohammad Ibn Zakariya al-Razi (864-930 ce), while others claim the first mention of the compound to have been by the Islamic writer Geber (probably born about 1270). In any case, European scientists apparently did not discover sulfuric acid on their own until the sixteenth century, when the Belgian scientist Johann Baptista van Helmont (1579–1644) described its preparation by adding water to the gas formed when sulfur was burned. The discovery of sulfuric acid proved to be an important development in the early history of modern chemistry. For the first time, it gave chemists an acid far stronger than the vinegar with which they previously had to work in analyzing mixtures and making new chemical compounds.

HOW IT IS MADE

The first commercially successful method for making sulfuric acid was developed in 1746 by English physician, chemist, and inventor John Roebuck (1718–1794). Roebuck's method is called the lead chamber process because the acid is made in large containers lined with lead. The lead chamber process involves three primary steps: the combustion of sulfur to produce sulfur dioxide; the conversion of sulfur dioxide to sulfur trioxide; and the reaction of sulfur trioxide with water to make sulfuric acid:

S + O₂ → SO₂

2SO₂ + O₂ → SO₃

SO₃ + H₂O → H₂SO₄

Although the process looks fairly simple, the reactions are actually somewhat complex because of other compounds needed to make the reactions occur.

The second method for making sulfuric acid is known as the contact process. It was invented about 1830 by an English vinegar merchant from Bristol, Peregrine Phillips. The chemical reactions involved in Phillips' process are identical to those in the lead chamber process, but they are carried out over a catalyst of finely divided platinum metal. Phillips found that the yield obtained (the amount of raw material converted to useful product) was much higher than with the lead chamber process.

As it happens, little attention was paid to Phillips' discovery because there was not much demand for sulfuric acid at the time. It was not until the invention of synthetic dyes a few decades later that the compound became commercially important. But even then, the lead chamber process was the preferred method for making sulfuric acid. Over time, improvements were made in the contact process, and it gradually became more and more popular. Today, nearly all of the sulfuric acid produced is manufactured by some modification of Peregrine Phillips' method.

COMMON USES AND POTENTIAL HAZARDS

The most important single use of sulfuric acid is for the production of phosphoric acid (H₃PO₄), which in turn is used to make fertilizers. About 70 percent of all the sulfuric acid used in the United States goes to this application. Some other uses of sulfuric acid include:

• As the electrolyte in lead storage batteries (the liquid through which charged particles flow);
• For the processing of gasoline and other petrochemicals, as a way of removing impurities present in the products;

• As a cleaning agent for metal surfaces, especially prior to their being plated with a second metal;
• In the manufacture of explosives, dyes, glues, pigments, rayon, and films;
• As a catalyst in a variety of industrial chemical and research chemical reactions; and
• In the processing of ores in preparation for the extraction of metals.

Interesting Facts

• Sulfuric acid's common name is oil of vitriol. That name comes from the fact that it was once produced from either iron(II) sulfate, known as "green vitriol," or from copper(II) sulfate, known as "blue vitriol."
• The conversion of sulfur dioxide to sulfur trioxide in the manufacture of sulfuric acid does not occur very readily. That step controls the efficiency with which the acid can be made. Phillips' great breakthrough was to find a catalyst that made that reaction take place more easily. Later, researchers found an even more efficient catalyst, vanadium pentoxide (V₂O₅). Today, vanadium pentoxide is still the most popular catalyst in the production of sulfuric acid.

Words to Know

CATALYST

A material that increases the rate of a chemical reaction without undergoing any change in its own chemical structure.

MISCIBLE

Able to be mixed; especially applies to the mixing of one liquid with another.

Sulfuric acid is a highly corrosive material that causes severe damage to the skin, eyes, and respiratory system. If spilled on the skin or eyes, it can cause inflammation, burns, and blistering, and cause serious damage to one's vision. If swallowed, it causes severe burns of the gastrointestinal tract and irreversible damage to tissue and organs. Any accident in which sulfuric acid is inhaled, swallowed, or spilled on the body requires immediate medical attention.

FOR FURTHER INFORMATION

"Chemical of the Week: Sulfuric Acid." Science is Fun. http://scifun.chem.wisc.edu/chemweek/Sulf&top/Sulf&Top.html (accessed on November 15, 2005).

"Chronic Toxicity Summary: Sulfuric Acid." Office of Environmental Health Hazard, State of California. http://www.oehha.org/air/chronic_rels/pdf/sulfuric.pdf (accessed on November 15, 2005).

"Sulfuric Acid." In World of Scientific Discovery. 2nd ed. Detroit: Gale Group, 1999.

"Sulfuric Acid." National Safety Council. http://www.nsc.org/library/chemical/sulfuric.htm (accessed on November 15, 2005).

"Sulfuric Acid: Production and Uses." Aus-e-tute. http://www.ausetute.com.au/sulfacid.html (accessed on November 15, 2005).

See AlsoPhosphoric Acid; Sulfur Dioxide

Sulfuric Acid

Sulfuric acid, H₂SO₄, is a strong mineral acid, which is a viscous (thick and syrupy), oily liquid that has for years been the most widely used chemical in the world. Normally found in a liquid state, sulfuric acid has a density of 1.84 g/cm³ and is soluble in water. Its melting point is about 50°F (10°C) and its boiling point is approximately 640°F (337°C). In the 2000s, over 165 million tonnes (metric tons; which is equivalent to 364 billion lb [165 billion kg]) of sulfuric acid are produced each year. It is considered the second most produced chemical, besides drinkable water. It is also one of the least expensive acids, which makes it a favorite of industries around the world. It is used in the production of fertilizers and as an industrial catalyst (a substance which speeds up chemical reactions). It is also used in large amounts in oil refining and waste-water processing.

Today, it is generally considered that sulfuric acid was first called oil of vitriol when Islamic alchemist, astronomer, and physicist Jabir ibn Hayyan (c. 721−c. 815) discovered it in the eighth century. European alchemists also called it oil of vitriol, along with spirit of vitriol and vitriol. It was a very popular chemical to alchemists across Asia and Europe from the eighth century to the sixteenth century, and in later centuries by chemists. In the seventeenth century, German-Dutch alchemist and chemist Johann Glauber (1604−1670) combined sulfur with saltpeter (potassium nitrate) and heated the combination with steam to make sulfuric acid. Around 1735, sulfuric acid was first mass produced by English pharmacist Joshua Ward in glass containers. Then, about 15 years later, English inventor John Roebuck (1718−1794) used a lead chamber process that made its production more efficient and less costly. The process was improved upon over the next eighty years. In 1831, English merchant Peregrine Phillips designed the contact process for producing sulfuric acid. His patented process is now the standard way of producing sulfuric acid in the 2000s.

One of the major uses of sulfuric acid is in the production of fertilizers. Phosphate rock is treated with sulfuric acid to produce water soluble phosphates, which are essential for plant growth and survival. It is also the acid used in car batteries. Automobile batteries contain lead, lead oxide, and sulfuric acid. These lead storage batteries are used because they can not only provide the electric current needed to start a car, but can be recharged by the car’s electrical system while the car is running.

Sulfuric acid is one of the major components of acid rain. Coal contains sulfur as a natural impurity and when coal is burned sulfur dioxide (SO₂) and sulfur trioxide (SO₃) gases are produced. Sulfur trioxide then reacts with water in the air, creating sulfuric acid. This acid rain can damage buildings, corrode metal, and destroy plant and animal life. Acid rain is an increasing problem not only in major industrialized nations, but also in neighboring countries that are downwind, since pollutants produced by a country do not stay in the air above that country.

One of the major industrial uses of sulfuric acid is as a dehydrating agent (a substance that removes water from other substances). Sulfuric acid is an extremely effective dehydrating agent. Upon contact with living tissue it kills cells by removing water from them.

Sulfuric acid

Sulfuric acid, H2SO4, is a viscous (thick and syrupy), oily liquid which has for years been the most widely used chemical in the world. Over 100 billion lb (45 billion kg) of sulfuric acid are produced each year. It is also one of the least expensive acids, which makes it a favorite of industries around the world. It is used in the production of fertilizers and as an industrial catalyst (a substance which speeds up chemical reactions ).

One of the major uses of sulfuric acid is in the production of fertilizers. Phosphate rock is treated with sulfuric acid to produce water soluble phosphates, which are essential for plant growth and survival. It is also the acid used in car batteries. Automobile batteries contain lead , lead oxide, and sulfuric acid. These lead storage batteries are used because they can not only provide the electric current needed to start a car, but can be recharged by the car's electrical system while the car is running.

Sulfuric acid is one of the major components of acid rain . Coal contains sulfur as a natural impurity and when coal is burned sulfur dioxide (SO2) and sulfur trioxide (SO3) gases are produced. Sulfur trioxide then reacts with water in the air, creating sulfuric acid. This acid rain can damage buildings, corrode metal , and destroy plant and animal life. Acid rain is an increasing problem not only in major industrialized nations, but also in neighboring countries that are downwind, since pollutants produced by a country do not stay in the air above that country.

One of the major industrial uses of sulfuric acid is as a dehydrating agent (a substance that removes water from other substances). Sulfuric acid is an extremely effective dehydrating agent. Upon contact with living tissue it kills cells by removing water from them.

sul·fu·ric ac·id • n. a strong acid made by oxidizing solutions of sulfur dioxide, H₂SO₄, and used in large quantities as an industrial and laboratory reagent. The concentrated form is an oily, dense, corrosive liquid.