Sulfuric Acid: Creation, Properties, Health
- Sylvia Rose
- 2 days ago
- 7 min read
Sulfuric acid is a powerful chemical compound. A colorless, thick liquid with a sharp smell, it's often called the King of Acids due to its highly corrosive nature. Uses include batteries, drain cleaners and as a solvent.
Sulfuric acid (H2SO4) is a mineral acid. It's also used in lead-acid batteries, popular despite the rise of lithium ion. A colorless to slightly yellow viscous liquid, it's soluble in water and vigorously releases heat on mixing.
The exothermic reaction is an important consideration when handling and diluting the acid. Sulfuric acid is highly corrosive, thus effective as a solvent.
How Sulfuric Acid is Created
The most common industrial method for producing sulfuric acid is the Contact Process. This method oxidizes sulfur dioxide (SO₂) to sulfur trioxide (SO3), which is dissolved in water to produce sulfuric acid.
1. Production of Sulfur Dioxide (SO2): Sulfur is burned in air or oxygen to produce SO2. Alternatively, SO2 can be obtained from roasting sulfide ores.
2. Conversion of Sulfur Dioxide to Sulfur Trioxide (SO₃): The SO2 is then passed over a vanadium pentoxide (V2O5) catalyst to convert it to SO3. Carefully control of temperature maximizes yield of SO3.
3. Absorption of Sulfur Trioxide in Sulfuric Acid: SO3 is absorbed into concentrated sulfuric acid (98-99%) to form oleum (H2S2O7), also known as fuming sulfuric acid.
Microbes Producing Sulfuric Acid
Sulfur-oxidizing bacteria like Thiobacillus thiooxidans and Acidithiobacillus ferrooxidans, can produce sulfuric acid. The bacteria derive energy by oxidizing sulfur compounds like elemental sulfur, sulfides, and thiosulfates.
This process generates sulfuric acid as a byproduct. It can contribute to acid mine drainage and the bioleaching of metals from ores. In areas of acid mine drainage pH drops to below 4, decimating aquatic life.
Oleum is diluted with water to make the desired concentration of sulfuric acid. This process can produce millions of tons of sulfuric acid annually, meeting the high demand.
Occurrence in Nature
Sulfuric acid can occur naturally. It's found in volcanic emissions, as a component of acid rain, and in some mineral deposits. Sulfur-eating microbes also contribute to its natural formation.
Due to its strong affection for water, sulfuric acid in pure form is rare. It can appear in geological formations.
Acid rain happens when sulfur dioxide from both natural and man-made sources reacts with atmospheric moisture. Acid rain has decreased in many parts of world due to emissions controls.
Discovery
Exact date of discovery is debated. Jabir ibn Hayyan (Geber), an 8th-century Persian alchemist, is often credited with its initial discovery.
In the 16th century, alchemist Basil Valentine studies its production. Large-scale production methods of the 18th century are still used today, improved by Joseph Louis Gay-Lussac and others.
Historical Precedents
The Mesopotamians have no name for "sulfuric acid" as a specific chemical, but they know vitriols. From these hydrated sulfates sulfuric acid can be derived. The Sumerians classify different types of vitriols based on color. This carries over into later alchemy.
Although the Romans don't have commercially produced sulfuric acid, they use sulfur, an essential component in the production of sulfuric acid. Romans use sulfur for such purposes as fire for pyrotechnics.
They also apply it as an insecticide and in some medical mixtures. The Romans know burning sulfur produces a choking gas. This, when combined with moisture, can form sulfuric acid.
Scientific Properties & Characteristics
Strong Acid: Sulfuric acid is a strong diprotic acid, meaning it can donate two protons (H+) in water. This contributes significantly to its reactivity.
With a density of 1.84 g/cm³, it's over 1.8 times heavier than water.
Powerful Solvent: It's a powerful solvent due to its high polarity and strong hydrogen bonding capabilities. It can dissolve many substances other solvents cannot.
Metals resistant to sulfuric acid corrosion include lead, tungsten, tantalum, platinum, gold, silver, iridium and zirconium. Some of these metals dissolve in aqua regia, a mix of hydrochloric and nitric acid.
Hygroscopic: Sulfuric acid is hygroscopic, readily absorbing moisture from the air. It's used as a drying agent in some applications.
Dehydrating Agent: Sulfuric acid removes water molecules from other compounds and can cause charring. Concentrated sulfuric acid reacts with sugar to form a blackened carbon mass.
Oxidizing Agent: At high concentrations and temperatures, sulfuric acid is an oxidizing agent. It can accept electrons from other substances.
Viscosity: The concentrated form is a viscous liquid due to strong intermolecular hydrogen bonding. It has a thick, syrup-like consistency.
Sulfuric acid's solvent abilities are in its strong acidic nature, enabling it to dehydrate materials efficiently. In oil refining, sulfuric acid helps separate impurities from hydrocarbons.
In metal processing, it strips away oxide layers to prepare surfaces for further treatment. Water treatment facilities use it to neutralize alkaline waste.
Corrosiveness of Sulfuric Acid
Corrosiveness of sulfuric comes comes from strong acidity and ability to dehydrate and oxidize organic materials. High concentrations of hydrogen ions (H+) attack materials to break chemical bonds.
Dehydration further amplifies corrosive action, especially on organic tissues. Sulfuric acid reacts vigorously with metals, minerals, and organic materials. It can also dissolve polycarbonates, but not Teflon.
Sulfuric Acid & the Human Body
Sulfuric acid is dangerous to human health. Skin contact creates severe burns, tissue damage and scarring. Ingestion causes internal burns, corrosion of mouth, throat and stomach, organ damage and death.
Inhalation of sulfuric acid fumes causes respiratory irritation, pulmonary edema and permanent lung damage. Handle sulfuric acid with extreme caution. Use personal protective equipment (PPE) like gloves, goggles and respirators.
Sulfuric Acid in Chemical Warfare
While sulfuric acid itself isn't a typical nerve agent or specifically designed chemical weapon, it can be used as such. It inflicts severe burns and disfigurement, incapacitating and killing victims. Sulfuric acid as a weapon is a violation of human rights and international law.
Sulfuric Acid: Robots & Machines
Sulfuric acid can damage robots and machines. The acid corrodes metal components, damages electronic circuitry, degrade plastic or rubber parts and melts silicone.
Specialized robots designed for hazardous environments are constructed with materials resistant to acid corrosion. Industries handling sulfuric acid use stainless steel or other acid-resistant materials in equipment.
Stainless steel is not impermeable and can be dissolved with sulfuric acid gradually. The rate and extent of corrosion depend on factors like acid concentration, type of stainless steel and temperature.
Highly concentrated sulfuric acid can dissolve silver but the reaction is slow, more so at low temperatures. Reaction of silver and concentrated sulfuric acid produce silver sulfate (Ag2SO4) and hydrogen gas.
Lead-Acid Batteries
Despite increasing popularity of lithium-ion, lead-acid batteries are favored in automotive and industrial settings. They're low-cost and reliable.
Lead-acid batteries are best suited to low speeds and short distances, such as in golf carts, forklifts and neighborhood electric vehicles. They're used as auxiliary batteries in hybrid and electric vehicles.
Lead-acid batteries are recycled with over 90% efficiency. They're dismantled to their constituent parts: lead, plastic and acid. The lead is melted, purified, and formed into ingots to make new batteries.
Plastic casing is transformed into pellets, which can be reused in new cases or other plastic items. Acid is recycled, neutralized or transformed to sodium sulfate, a drying agent, detergent filler and laxative.
Uses of Sulfuric Acid
Fertilizer production: A major application is in the production of phosphate fertilizers. It is essential in producing phosphoric acid, a foundation of many fertilizers.
Petroleum refining: Used as a catalyst in various refining processes, it's especially favored for producing high-octane fuels through alkylation.
Chemical synthesis: Sulfuric acid is a key reactant in production of chemicals including detergents, plastics, and synthetic fibers.
Metal processing: It's used in pickling (cleaning) metals, refining, and in the extraction of metals from ores.
Battery production: Sulfuric acid is the electrolyte in lead-acid batteries, helping power millions of vehicles.
Wastewater treatment: It's used to adjust pH and remove certain contaminants.
Drain cleaning: It's effective but very dangerous.
Facts about Sulfuric Acid
Production of sulfuric acid is often used as an indicator of a country's industrial strength. Millions of tons of sulfuric acid are produced worldwide per year, making it one of the most manufactured chemicals.
Sulfuric acid is sometimes referred to as "oil of vitriol," a name going back to early alchemy.
The planet Venus has clouds of sulfuric acid droplets.
Some onions release weak sulfuric acid when cut, making eyes sting and water.
In diluting sulfuric acid, always add the acid to water. Adding water to acid causes eruptive splashing and boiling due to the exothermic reaction.
Sulfuric acid is a major component in production of titanium dioxide, a pigment used in paint, plastics, cosmetics and paper.
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