1 harsh or corrosive in tone; "an acerbic tone piercing otherwise flowery prose"; "a barrage of acid comments"; "her acrid remarks make her many enemies"; "bitter words"; "blistering criticism"; "caustic jokes about political assassination, talk-show hosts and medical ethics"; "a sulfurous denunciation" [syn: acerb, acerbic, acid, acrid, bitter, blistering, caustic, sulfurous, sulphurous, venomous, virulent]
2 of a substance, especially a strong acid; capable of destroying or eating away by chemical action [syn: caustic, corrosive, erosive]
Sulfuric acid H2SO4, is a strong mineral acid. It is soluble in water at all concentrations. It was once known as oil of vitriol, coined by the 8th-century Muslim alchemist Jabir ibn Hayyan (Geber) after his discovery of the chemical.
Sulfuric acid has many applications, and is one of the top products of the chemical industry. World production in 2001 was 165 million metric tons, with an approximate value of US$8 billion. Principal uses include ore processing, fertilizer manufacturing, oil refining, wastewater processing, and chemical synthesis. Its ability to produce foul-smelling sulfur compounds has lent the word vitriol the additional meaning "bitter, abusive language".
Many proteins are made of sulfur-containing amino acids (such as cysteine and methionine) which produce sulfuric acid (or sulfate ion, SO42- at neutral pH) when metabolized by the body.
OccurrencePure undiluted sulfuric acid is not encountered on Earth, due to sulfuric acid's great affinity for water. Apart from that, sulfuric acid is a constituent of acid rain, which is formed by atmospheric oxidation of sulfur dioxide in the presence of water, i.e., oxidation of sulfurous acid. Sulfur dioxide is the main byproduct produced when sulfur-containing fuels such as coal or oil are burnt.
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-coloured, toxic streams. The oxidation of iron sulfide pyrite (FeS2) by molecular oxygen produces iron(II), or Fe2+:
- 2 FeS2 + 7 O2 + 2 H2O → 2 Fe2+ + 4 SO42− + 4 H+
The Fe2+ can be further oxidized to Fe3+, according to:
- 4 Fe2+ + O2 + 4 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 AMD produced by this process.
AMD can also produce sulfuric acid at a slower rate, so that the acid neutralizing capacity (ANC) of the aquifer can neutralise 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-neutralisation reaction with the minerals.
Extraterrestrial sulfuric acidSulfuric acid is produced in the upper atmosphere of Venus by the sun's photochemical action on carbon dioxide, sulfur dioxide, and water vapour. Ultraviolet photons of wavelengths less than 169 nm can photodissociate carbon dioxide into carbon monoxide and atomic oxygen. Atomic oxygen is highly reactive. When it reacts with sulfur dioxide, a trace component of the Venerian atmosphere, the result is sulfur trioxide, which can combine with water vapor, another trace component of Venus's atmosphere, to yield sulfuric acid.
- CO2 → CO + O
- SO2 + O → SO3
- SO3 + H2O → H2SO4
- SO2 + O → SO3
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.
This is then oxidised to sulfur trioxide using oxygen in the presence of a vanadium(V) oxide catalyst.
- (2) 2 SO2 + O2(g) → 2 SO3(g) (in presence of 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) + H2O(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)
Forms of sulfuric acidAlthough nearly 100% sulfuric acid can be made, this loses SO3 at the boiling point to produce 98.3% acid. The 98% grade (18M) is more stable in storage, and is the usual form of what is described as concentrated sulfuric acid. Other 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 United States Pharmacopoeia (USP) grade are used for making pharmaceuticals and dyestuffs.
When high concentrations of SO3(g) are added to sulfuric acid, H2S2O7, called pyrosulfuric acid, fuming sulfuric acid or 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 conductivityAnhydrous H2SO4 is a very polar liquid, having a dielectric constant of around 100. It has a high electrical conductivity, caused by dissociation through protonating itself, a process known as autoprotolysis, or autoionization.
- 2 H2SO4 H3SO4+ + HSO4−
UsesSulfuric acid is a very important commodity chemical, and indeed, a nation's sulfuric acid production is a good indicator of its industrial strength. The major use (60% of total production worldwide) for sulfuric acid is in the "wet method" for the production of phosphoric acid, used for manufacture of phosphate fertilizers as well as trisodium phosphate for detergents. In this method, phosphate rock is used, and more than 100 million tonnes are processed annually. This raw material is shown below as fluorapatite, though the exact composition may vary. This is treated with 93% sulfuric acid to produce calcium sulfate, hydrogen fluoride (HF) and phosphoric acid. The HF is removed as hydrofluoric acid. The overall process can be represented as:
Sulfuric acid is used in large quantities by the iron and steelmaking industry to remove oxidation, 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.
Ammonium sulfate, an important nitrogen fertilizer, is most commonly produced as a byproduct from coking plants supplying the iron and steel making plants. Reacting the 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 aluminium sulfate, also known as paper maker's alum. This can react with small amounts of soap on paper pulp fibers to give gelatinous aluminium carboxylates, which help to coagulate the pulp fibers into a hard paper surface. It is also used for making aluminium hydroxide, which is used at water treatment plants to filter out impurities, as well as to improve the taste of the water. Aluminum sulfate is made by reacting bauxite with sulfuric acid:
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 nylon. It is used for making hydrochloric acid from salt via the Mannheim process. Much H2SO4 is used in petroleum refining, for example as a catalyst for the reaction of isobutane with isobutylene to give isooctane, a compound that raises the octane rating of gasoline (petrol). Sulfuric acid is also important in the manufacture of dyestuffs, pigments (such as titanium dioxide), 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 cycleThe sulfur-iodine cycle is a series of thermo-chemical processes used to obtain hydrogen. It consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen.
The sulfur and iodine compounds are recovered and reused, hence the consideration of the process as a cycle. This process is 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.
HistoryThe corrosive properties of sulfuric acid are accentuated by its highly exothermic reaction with water. Hence burns from sulfuric acid are potentially more serious than those of comparable strong acids (e.g. hydrochloric acid), as there is additional tissue damage due to dehydration and particularly due to the heat liberated by the reaction with water; i.e. secondary thermal damage. The danger is obviously greater with more concentrated preparations of sulfuric acid, but it should be remembered that even the normal laboratory "dilute" grade (approx. 1 M, 10%) will char paper by dehydration if left in contact for a sufficient amount of time. Solutions equal to or stronger than 1.5 M should be labeled CORROSIVE, while solutions greater than 0.5 M but less than 1.5 M should be labeled IRRITANT. Fuming sulfuric acid (oleum) is not recommended for use in schools due to it being quite hazardous. The standard first aid treatment for acid spills on the skin is, as for other corrosive agents, irrigation with large quantities of water. However, the acid should be neutralised first by rinsing with a base (e.g. calcium hydroxide solution), because the water used in washing will react with the acid and increase the chance of secondary damage. 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 hazardsAlthough sulfuric acid is non-flammable, contact with metals in the event of a spillage can lead to the liberation of hydrogen gas. The dispersal of acid aerosols and gaseous 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.
Legal restrictionsInternational 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.
In the United States of America, sulfuric acid is included in List II of the 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.
In fictionIn several films, cartoons and TV shows, especially Science-Fiction shows and films, sulfuric acid is sometimes depicted as a bubbling green steaming liquid, sometimes capable of dissolving almost anything in an instant. This is purely for visual appeal, since boiling green acid is more dangerous-looking than the actual clear and syrupy form of sulfuric acid. 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, Nineteen Eighty-Four by George Orwell and Brighton Rock by Graham Greene. 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 graphic novel, Shake Girl, is dedicated to over 100 Cambodian victims who have suffered from burns caused by sulfuric acid. In the movie Untraceable,Griffin Dowd ( played by Colin Hanks ) is submerged in sulfuric acid.
- Institut National de Recherche et de Sécurité. (1997). "Acide sulfurique". Fiche toxicologique n°30, Paris: INRS, 5 pp.
- Handbook of Chemistry and Physics, 71st edition, CRC Press, Ann Arbor, Michigan, 1990.
- Agamanolis DP. Metabolic and toxic disorders. In: Prayson R, editor. Neuropathology: a volume in the foundations in diagnostic pathology series. Philadelphia: Elsevier/Churchill Livingstone, 2005; 413-315.
vitriolic in Arabic: حمض كبريتيك
vitriolic in Bosnian: Sumporna kiselina
vitriolic in Breton: Trenkenn sulfurek
vitriolic in Catalan: Àcid sulfúric
vitriolic in Czech: Kyselina sírová
vitriolic in Danish: Svovlsyre
vitriolic in German: Schwefelsäure
vitriolic in Estonian: Väävelhape
vitriolic in Modern Greek (1453-): Θειικό οξύ
vitriolic in Spanish: Ácido sulfúrico
vitriolic in Esperanto: Sulfata acido
vitriolic in Persian: اسید سولفوریک
vitriolic in French: Acide sulfurique
vitriolic in Galician: Ácido sulfúrico
vitriolic in Korean: 황산
vitriolic in Indonesian: Asam sulfat
vitriolic in Icelandic: Brennisteinssýra
vitriolic in Italian: Acido solforico
vitriolic in Hebrew: חומצה גופרתית
vitriolic in Latin: Acidum sulphuricum
vitriolic in Latvian: Sērskābe
vitriolic in Lithuanian: Sieros rūgštis
vitriolic in Hungarian: Kénsav
vitriolic in Malay (macrolanguage): Asid sulfurik
vitriolic in Dutch: Zwavelzuur
vitriolic in Japanese: 硫酸
vitriolic in Norwegian: Svovelsyre
vitriolic in Norwegian Nynorsk: Svovelsyre
vitriolic in Low German: Swevelsüür
vitriolic in Polish: Kwas siarkowy(VI)
vitriolic in Portuguese: Ácido sulfúrico
vitriolic in Romanian: Acid sulfuric
vitriolic in Russian: Серная кислота
vitriolic in Simple English: Sulfuric acid
vitriolic in Slovak: Kyselina sírová
vitriolic in Slovenian: Žveplova kislina
vitriolic in Serbian: Сумпорна киселина
vitriolic in Serbo-Croatian: Sumporna kiselina
vitriolic in Finnish: Rikkihappo
vitriolic in Swedish: Svavelsyra
vitriolic in Thai: กรดกำมะถัน
vitriolic in Vietnamese: Axít sulfuric
vitriolic in Turkish: Sülfürik asit
vitriolic in Ukrainian: Сульфатна кислота
vitriolic in Venetian: Àsido solfòrico
vitriolic in Chinese: 硫酸
acerbic, acid, acidulous, acrid, acrimonious, antagonistic, antipathetic, asperous, astringent, belligerent, biting, bitter, caustic, clashing, colliding, conflicting, cutting, despiteful, double-edged, edged, envenomed, escharotic, fierce, full of hate, harsh, hateful, hostile, incisive, irritating, keen, malevolent, malicious, malignant, mordacious, mordant, nose-tickling, penetrating, piercing, piquant, poignant, pungent, quarrelsome, rancorous, repugnant, rigorous, rough, scathing, set against, severe, sharp, sore, sour, spiteful, stabbing, stinging, strident, stringent, tart, trenchant, vehement, venenate, venomous, violent, virulent