Sulfuric acid

Sulfuric (or sulphuric) acid, chemical synthesis.

Many metabolized by the body.

Manufacture

Main article: Contact process

Sulfuric acid is produced from contact process.

In the first step, sulfur dioxide.

(1) SO₂(g)

This is then oxidised to catalyst.

(2) 2 SO₂ + O₂(g) → V₂O₅)

Finally the sulfur trioxide is treated with water (usually as 97-98% H₂SO₄ containing 2-3% water) to produce 98-99% sulfuric acid.

(3) SO₃(g) + l) → H₂SO₄(l)

Note that directly dissolving SO₃ in water is not practical due to the highly exothermic nature of the reaction, forming a corrosive mist instead of a liquid. Alternatively, SO₃ can be absorbed into H₂SO₄ to produce oleum (H₂S₂O₇), which may then be mixed with water to form sulfuric acid.

(3) H₂SO₄(l) + SO₃ → H₂S₂O₇(l)

Oleum is reacted with water to form concentrated H₂SO₄.

(4) H₂S₂O₇(l) + H₂O(l) → 2 H₂SO₄(l)

Physical properties

Forms of sulfuric acid

Although nearly 100% sulfuric acid can be made, this loses concentrations are used for different purposes. Some common concentrations are

• 10%, dilute sulfuric acid for laboratory use,
• 33.5%, battery acid (used in lead-acid batteries),
• 62.18%, chamber or fertilizer acid,
• 77.67%, tower or Glover acid,
• 98%, concentrated acid.

Different purities are also available. Technical grade H₂SO₄ is impure and often colored, but is suitable for making fertilizer. Pure grades such as US dyestuffs.

When high concentrations of SO_{3(oleum or, less commonly, Nordhausen acid, is formed. Concentrations of oleum are either expressed in terms of% SO3 (called% oleum) or as% H2SO4 (the amount made if H2O were added); common concentrations are 40% oleum (109% H2SO4) and 65% oleum (114.6% H2SO4). Pure H2S2O7 is a solid with melting point 36°C.}

Polarity and conductivity

dielectric constant of around 100. It has a high electrical conductivity, caused by dissociation through protonating itself, a process known as autoprotolysis.^[2]

2 H₂SO₄ ⇌ H₃SO₄⁺ + HSO₄⁻

The equilibrium constant for the autoprotolysis is^[2]

K_ap(25°C)= [H₃SO₄⁺][HSO₄⁻] = 2.7 × 10⁻⁴.

The comparable equilibrium constant for water, K_w is 10⁻¹⁴, a factor of 10¹⁰ (10 billion) smaller.

In spite of the viscosity of the acid, the effective Grotthuss mechanism in water), making sulfuric acid a good conductor. It is also an excellent solvent for many reactions.

The H₂S₂O₇ (3.6), H₂O (0.1).^[2]

Chemical properties

Reaction with water

The hydronium ions, by

H₂SO₄ + H₂O → H₃O⁺ + HSO₄⁻,

and then

HSO₄⁻ + H₂O → H₃O⁺ + SO₄²⁻.

Because the hydration of sulfuric acid is caramel.

Other reactions of sulfuric acid

As an acid, sulfuric acid reacts with most copper(II) oxide with sulfuric acid:

H₂O

Sulfuric acid can also be used to displace weaker acids from their salts. Reaction with acetic acid:

H₂SO₄ + CH₃COOH

Similarly, reacting sulfuric acid with Fischer esterification and dehydration of alcohols.

Sulfuric acid reacts with most metals via a single displacement reaction to produce sulfur dioxide rather than hydrogen.

H₂(g) + FeSO₄(aq)

SO₂(g)

Environmental aspects

Sulfuric acid is a constituent of sulfurous acid. Sulfur dioxide is the main byproduct produced when sulfur-containing fuels such as coal or oil are burned.

Sulfuric acid is formed naturally by the oxidation of sulfide minerals, such as iron sulfide. The resulting water can be highly acidic and is called Acid Mine Drainage (AMD). This acidic water is capable of dissolving metals present in sulfide ores, which results in brightly-colored, toxic streams. The oxidation of iron sulfide pyrite by molecular oxygen produces iron(II), or Fe²⁺:

2 H⁺.

The Fe²⁺ can be further oxidized to Fe³⁺, according to:

4 Fe²⁺ + H⁺ → 4 Fe³⁺ + 2 H₂O,

and the Fe³⁺ produced can be precipitated as the hydroxide or hydrous oxide. The equation for the formation of the hydroxide is

Fe³⁺ + 3 H₂O → Fe(OH)₃ + 3 H⁺.

The iron(III) ion ("ferric iron", in casual nomenclature) can also oxidize pyrite. When iron(III) oxidation of pyrite occurs, the process can become rapid. pH values below zero have been measured in ARD produced by this process.

ARD can also produce sulfuric acid at a slower rate, so that the Acid Neutralization Capacity (ANC) of the aquifer can neutralize the produced acid. In such cases, the Total Dissolved solids (TDS) concentration of the water can be increased form the dissolution of minerals from the acid-neutralization reaction with the minerals.

Extraterrestrial sulfuric acid

Sulfuric acid is produced in the upper atmosphere of Venus by the sun's sulfur trioxide, which can combine with water vapor, another trace component of Venus' atmosphere, to yield sulfuric acid.

O

SO₃

SO₃ + H₂O → H₂SO₄

In the upper, cooler portions of Venus's atmosphere, sulfuric acid exists as a liquid, and thick sulfuric acid clouds completely obscure the planet's surface when viewed from above. The main cloud layer extends from 45–70 km above the planet's surface, with thinner hazes extending as low as 30 and as high as 90 km above the surface.

Infrared spectra from NASA's Galileo mission show distinct absorptions on Jupiter's moon Europa that have been attributed to one or more sulfuric acid hydrates. The interpretation of the spectra is somewhat controversial. Some planetary scientists prefer to assign the spectral features to the sulfate ion, perhaps as part of one or more minerals on Europa's surface.^[3]

History of sulfuric acid

  The discovery of sulfuric acid is credited to the 8th century Albertus Magnus.

Sulfuric acid was known to medieval European alchemists as oil of vitriol, spirit of vitriol, or simply vitriol, among other names. The word vitriol derives from the Latin vitreus, 'glass', referring to the glassy appearance of the sulfate salts, which also carried the name vitriol. Salts called by this name included copper(II) sulfate (blue vitriol, or rarely Roman vitriol), zinc sulfate (white vitriol), iron(II) sulfate (green vitriol), iron(III) sulfate (vitriol of Mars), and cobalt(II) sulfate (red vitriol).

Vitriol was widely considered the most important Basilius Valentinus, .

In the 17th century, the German-Dutch chemist potassium nitrate, KNO₃), in the presence of steam. As saltpeter decomposes, it oxidizes the sulfur to SO₃, which combines with water to produce sulfuric acid. In 1736, Joshua Ward, a London pharmacist, used this method to begin the first large-scale production of sulfuric acid.

In 1746 in Birmingham, John Roebuck adapted this method to produce sulfuric acid in lead chamber process allowed the effective industrialization of sulfuric acid production. After several refinements, this method remained the standard for sulfuric acid production for almost two centuries.

Sulfuric acid created by John Roebuck's process only approached a 35–40% concentration. Later refinements to the lead-chamber process by French chemist sulfur trioxide, which could be passed through water to yield sulfuric acid in any concentration. However, the expense of this process prevented the large-scale use of concentrated sulfuric acid.

In 1831, British vinegar merchant Peregrine Phillips patented the contact process, which was a far more economical process for producing sulfur trioxide and concentrated sulfuric acid. Today, nearly all of the world's sulfuric acid is produced using this method.

Uses

  Sulfuric acid is a very important commodity chemical, and indeed, a nation's sulfuric acid production is a good indicator of its industrial strength.^[4] The major use (60% of total production worldwide) for sulfuric acid is in the "wet method" for the production of hydrofluoric acid. The overall process can be represented as:

H₃PO₄.

Sulfuric acid is used in large quantities by the rust and scale from rolled sheet and billets prior to sale to the automobile and white-goods industry. Used acid is often recycled using a Spent Acid Regeneration (SAR) plant. These plants combust spent acid with natural gas, refinery gas, fuel oil or other fuel sources. This combustion process produces gaseous sulfur dioxide (SO₂) and sulfur trioxide (SO₃) which are then used to manufacture "new" sulfuric acid. SAR plants are common additions to metal smelting plants, oil refineries, and other industries where sulfuric acid is consumed in bulk, as operating a SAR plant is much cheaper than the recurring costs of spent acid disposal and new acid purchases.

ammonia produced in the thermal decomposition of coal with waste sulfuric acid allows the ammonia to be crystallized out as a salt (often brown because of iron contamination) and sold into the agro-chemicals industry.

Another important use for sulfuric acid is for the manufacture of bauxite with sulfuric acid:

H₂O.

Sulfuric acid is used for a variety of other purposes in the chemical industry. For example, it is the usual acid catalyst for the conversion of cyclohexanoneoxime to caprolactam, used for making dyestuffs solutions and is the "acid" in lead-acid (car) batteries.

Sulfuric acid is also used as a general dehydrating agent in its concentrated form. See Reaction with water.

Sulfur-iodine cycle

The oxygen.

2 O2		(830°C)
O4		(120°C)
2 H2		(320°C)

The sulfur and endothermic and must occur at high temperatures, so energy in the form of heat has to be supplied.

The sulfur-iodine cycle has been proposed as a way to supply hydrogen for a hydrogen-based economy. It does not require hydrocarbons like current methods of steam reforming.

The sulfur-iodine cycle is currently being researched as a feasible method of obtaining hydrogen, but the concentrated, corrosive acid at high temperatures poses currently insurmountable safety hazards if the process were built on large-scale.

Safety

Laboratory hazards

The corrosive properties of sulfuric acid are accentuated by its highly corrosive agents, irrigation with large quantities of water: Washing should be continued for at least ten to fifteen minutes in order to cool the tissue surrounding the acid burn and to prevent secondary damage. Contaminated clothing must be removed immediately and the underlying skin washed thoroughly.

Preparation of the diluted acid can also be dangerous due to the heat released in the dilution process. It is essential that the concentrated acid is added to water and not the other way round, to take advantage of the relatively high heat capacity of water. Addition of water to concentrated sulfuric acid leads at best to the dispersal of a sulfuric acid aerosol, at worst to an explosion. Preparation of solutions greater than 6 M (35%) in concentration is the most dangerous, as the heat produced can be sufficient to boil the diluted acid: efficient mechanical stirring and external cooling (e.g. an ice bath) are essential.

Industrial hazards

Although sulfuric acid is non-flammable, contact with metals in the event of a spillage can lead to the liberation of sulfur dioxide is an additional hazard of fires involving sulfuric acid.

Sulfuric acid is not considered toxic besides its obvious corrosive hazard, and the main occupational risks are skin contact leading to burns (see above) and the inhalation of aerosols. Exposure to aerosols at high concentrations leads to immediate and severe irritation of the eyes, respiratory tract and mucous membranes: this ceases rapidly after exposure, although there is a risk of subsequent pulmonary edema if tissue damage has been more severe. At lower concentrations, the most commonly reported symptom of chronic exposure to sulfuric acid aerosols is erosion of the teeth, found in virtually all studies: indications of possible chronic damage to the respiratory tract are inconclusive as of 1997. In the United States, the permissible exposure limit (PEL) for sulfuric acid is fixed at 1 mg/m³: limits in other countries are similar. Interestingly there have been reports of sulfuric acid ingestion leading to vitamin B12 deficiency with subacute combined degeneration. The spinal cord is most often affected in such cases, but the optic nerves may show demyelination, loss of axons and gliosis.

Societal and cultural aspects

Metaphorical usage

Vitriol may be used metaphorically, as in a diatribe or verbal upbraiding.

In fiction

The use of sulfuric acid as a weapon in crimes of assault, known as "vitriol throwing", has at times been sufficiently common (if sensational) to make its way into novels and short stories. Examples include The Adventure of the Illustrious Client, by Arthur Conan Doyle, The Love of Long Ago, by Guy de Maupassant and Brighton Rock by Graham Greene. A band, My Vitriol, take their name from its use as a weapon in Brighton Rock. An episode of Saturday Night Live hosted by Mel Gibson included a parody Western sketch about "Sheriff Jeff Acid," who carries a flask of acid instead of a six shooter. The DC Comics villain Two Face was disfigured as a result of a vitriol throw. This crime is also mentioned in Nineteen Eighty-Four by George Orwell; the protagonist Winston Smith agrees to throw vitriol into a child's face if that would be "the Brotherhood's" order, and Winston's enemy O'Brien later uses those barbaric words to undermine his logic. The novel Veronika Decides to Die by Paulo Coelho talks of a girl who has attempted to commit suicide and ends up with vitriol poisoning. The doctor/therapist in this novel also writes a thesis on curing vitriol poisoning. The substance was also used by a young gangster in Season 6B, Episode 5 of The Sopranos as a form of torture.

Legal controls and regulation

International commerce of sulfuric acid is controlled under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances, 1988, which lists sulfuric acid under Table II of the convention as a chemical frequently used in the illicit manufacture of narcotic drugs or psychotropic substances.^[5]

In the United States of America, sulfuric acid is included in list of essential or precursor chemicals established pursuant to the Chemical Diversion and Trafficking Act. Accordingly, transactions of sulfuric acid—such as sales, transfers, exports from and imports to the United States—are subject to regulation and monitoring by the Drug Enforcement Administration.^[6][7][8]

References