Sulfuric acid is a
strongA strong acid is an acid that ionizes completely in an aqueous solution by losing one proton, according to the equationFor sulfuric acid which is diprotic, the "strong acid" designation refers only to dissociation of the first protonMore precisely, the acid must be stronger in aqueous solution than...
mineral acidA mineral acid is an acid derived from one or more inorganic compounds. A mineral acid is not organic and all mineral acids release hydrogen ions when dissolved in water.-Characteristics:...
with the molecular formula . Its historical name is oil of
vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called
sulfateIn inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
s. Sulfuric acid is soluble in
waterWater is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
at all concentrations.
Sulfuric acid has many applications, and is a central substance in the
chemical industryThe chemical industry comprises the companies that produce industrial chemicals. Central to the modern world economy, it converts raw materials into more than 70,000 different products.-Products:...
. Principal uses include lead-acid batteries for cars and other vehicles,
oreAn ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
processing,
fertilizerFertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
manufacturing,
oil refiningAn oil refinery or petroleum refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas...
, wastewater processing, and
chemical synthesisIn chemistry, chemical synthesis is purposeful execution of chemical reactions to get a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions...
.
History
The study of vitriol began in
ancient timesClassical antiquity is a broad term for a long period of cultural history centered on the Mediterranean Sea, comprising the interlocking civilizations of ancient Greece and ancient Rome, collectively known as the Greco-Roman world...
. Sumerians had a list of types of vitriol that they classified according to substance's color. Some of the earliest discussions on the origin and properties of vitriol are in the works of the Greek physician Dioscorides (first century AD) and the Roman naturalist
Pliny the ElderGaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...
(23–79 AD).
GalenAelius Galenus or Claudius Galenus , better known as Galen of Pergamon , was a prominent Roman physician, surgeon and philosopher...
also discussed its medical use. Metallurgical uses for vitriolic substances were recorded in the Hellenistic alchemical works of
Zosimos of PanopolisZosimos of Panopolis was an Egyptian or Greek alchemist and Gnostic mystic from the end of the 3rd and beginning of the 4th century AD. He was born in Panopolis, present day Akhmim in the south of Egypt, ca. 300. He wrote the oldest known books on alchemy, of which quotations in the Greek language...
, in the treatise
Phisica et Mystica, and the "Leyden Papyrus x".
Islamic alchemistsAlchemy and chemistry in Islam refers to the study of both traditional alchemy and early practical chemistry by scholars in the medieval Islamic world. The word alchemy was derived from the Arabic word كيمياء or kīmīāʾ...
Jābir ibn Hayyān (c. 721 – c. 815 AD), Razi (865 – 925 AD), and Jamal Din al-Watwat (d. 1318, wrote the book
Mabāhij al-fikar wa-manāhij al-'ibar), included vitriol in their mineral classification lists. Ibn Sina focused on its medical uses and different varieties of vitriol.
Sulfuric acid was called "oil of vitriol" by medieval European alchemists. There are mentions to it in the works of
Vincent of BeauvaisThe Dominican friar Vincent of Beauvais wrote the Speculum Maius, the main encyclopedia that was used in the Middle Ages.-Early life:...
and in the
Compositum de Compositis ascribed to
Albertus MagnusAlbertus Magnus, O.P. , also known as Albert the Great and Albert of Cologne, is a Catholic saint. He was a German Dominican friar and a bishop, who achieved fame for his comprehensive knowledge of and advocacy for the peaceful coexistence of science and religion. Those such as James A. Weisheipl...
. A passage from
Pseudo-GeberPseudo-Geber is the name assigned by modern scholars to an anonymous European alchemist born in the 13th century, sometimes identified with Paul of Taranto, who wrote books on alchemy and metallurgy, in Latin, under the pen name of "Geber". "Geber" is the shortened and Latinised form of the name...
´s
Summa Perfectionis was long considered to be the first recipe for sulfuric acid, but this was a misinterpretation.
In the 17th century, the German-Dutch chemist Johann Glauber prepared sulfuric acid by burning sulfur together with
saltpeterPotassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...
(
potassium nitratePotassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...
), in the presence of steam. As saltpeter decomposes, it oxidizes the sulfur to , which combines with water to produce sulfuric acid. In 1736,
Joshua WardJoshua Ward was a London pharmacist and an experimental chemist. In 1736, Ward heated saltpeter and as it decomposed the sulfur was oxidized to SO3, which combined with water to produce sulfuric acid. It was the first practical production of sulfuric acid on a large scale.-References:...
, a London pharmacist, used this method to begin the first large-scale production of sulfuric acid.
In 1746 in Birmingham,
John RoebuckThis article is about the English inventor. For the 19th century British politician, see John Arthur Roebuck.John Roebuck FRS was an English inventor who played an important role in the Industrial Revolution and who is known for developing the industrial-scale manufacture of sulfuric acid.-Life...
adapted this method to produce sulfuric acid in
leadLead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
-lined chambers, which were stronger, less expensive, and could be made larger than the previously used glass containers. This
lead chamber processThe lead chamber process was an industrial method used to produce sulfuric acid in large quantities. It has been largely supplanted by the contact 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
Joseph Louis Gay-Lussac- External links :* from the American Chemical Society* from the Encyclopædia Britannica, 10th Edition * , Paris...
and British chemist John Glover improved the yield to 78%. However, the manufacture of some
dyeA dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....
s and other chemical processes require a more concentrated product. Throughout the 18th century, this could only be made by
dry distillingDry distillation is the heating of solid materials to produce gaseous products . The method may or may not involve pyrolysis/thermolysis. The products are condensed and collected. This method usually requires higher temperatures than classical distillation. The method has been used to obtain...
minerals in a technique similar to the original
alchemicalAlchemy is an influential philosophical tradition whose early practitioners’ claims to profound powers were known from antiquity. The defining objectives of alchemy are varied; these include the creation of the fabled philosopher's stone possessing powers including the capability of turning base...
processes.
PyriteThe mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
(iron disulfide) was heated in air to yield
iron(II) sulfateIron sulfate or ferrous sulfate is the chemical compound with the formula FeSO4. Known since ancient times as copperas and as green vitriol, the blue-green heptahydrate is the most common form of this material...
, , which was oxidized by further heating in air to form
iron(III) sulfateIron sulfate , is the chemical compound with the formula Fe23, the sulfate of trivalent iron. Usually yellow, it is a rhombic crystalline salt and soluble in water at room temperature. It is used in dyeing as a mordant, and as a coagulant for industrial wastes. It is also used in pigments, and in...
, , which, when heated to 480 °C, decomposed to
iron(III) oxideIron oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron oxide , which is rare, and iron oxide , which also occurs naturally as the mineral magnetite. As the mineral known as hematite, Fe2O3 is the main...
and 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
vinegarVinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...
merchant Peregrine Phillips patented the
contact processThe contact process is the current method of producing sulphuric acid in the high concentrations needed for industrial processes. Platinum was formerly employed as a catalyst for the reaction, but as it is susceptible to poisoning by arsenic impurities in the sulfur feedstock, vanadium oxide is...
, 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.
Grades of sulfuric acid
Although nearly 99% sulfuric acid can be made, this loses at the boiling point to produce 98.3% acid. The 98% grade 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:
Mass fraction
H2SO4 |
Density
(kg/L) |
Concentration
(mol/L) |
Common name |
| 10% |
1.07 |
~1 |
dilute sulfuric acid |
| 29–32% |
1.25–1.28 |
4.2–5 |
battery acid
(used in lead–acid batteries) |
| 62–70% |
1.52–1.60 |
9.6–11.5 |
chamber acid
fertilizer acid |
| 78–80% |
1.70–1.73 |
13.5–14 |
tower acid
Glover acid |
| 95–98% |
1.83 |
~18 |
concentrated sulfuric acid |
"Chamber acid" and "tower acid" were the two concentrations of sulfuric acid produced by the
lead chamber processThe lead chamber process was an industrial method used to produce sulfuric acid in large quantities. It has been largely supplanted by the contact process....
, chamber acid being the acid produced in lead chamber itself (<70% to avoid contamination with
nitrosylsulfuric acidNitrosylsulfuric acid is the chemical compound with the formula NOHSO4.This salt is a source of the NO+ ion, It can also be viewed as the mixed acid anhydride of sulfuric acid and nitrous acid:...
) and tower acid being the acid recovered from the bottom of the Glover tower. They are now obsolete as commercial concentrations of sulfuric acid, although they may be prepared in the laboratory from concentrated sulfuric acid if needed. In particular, "10M" sulfuric acid (the modern equivalent of chamber acid, used in many
titrationTitration, also known as titrimetry, is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of an identified analyte. Because volume measurements play a key role in titration, it is also known as volumetric analysis. A reagent, called the...
s) is prepared by slowly adding 98% sulfuric acid to an equal volume of water, with good stirring: the temperature of the mixture can rise to 80 °C (176 °F) or higher.
When high concentrations of gas are added to sulfuric acid, , called
pyrosulfuric acid,
fuming sulfuric acid or
oleum or, less commonly,
Nordhausen acid, is formed. Concentrations of oleum are either expressed in terms of % (called % oleum) or as % (the amount made if were added); common concentrations are 40% oleum (109% ) and 65% oleum (114.6% ). Pure is a solid with melting point 36°C.
Pure sulfuric acid is a viscous clear liquid, like oil, and this explains the old name of the acid ('oil of vitriol').
Commercial sulfuric acid is sold in several different purity grades. Technical grade is impure and often colored, but is suitable for making fertilizer. Pure grades such as
United States PharmacopeiaThe United States Pharmacopeia is the official pharmacopeia of the United States, published dually with the National Formulary as the USP-NF. The United States Pharmacopeial Convention is the nonprofit organization that owns the trademark and copyright to the USP-NF and publishes it every year...
(USP) grade are used for making pharmaceuticals and
dyeA dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....
stuffs.
AnalyticalAnalytical chemistry is the study of the separation, identification, and quantification of the chemical components of natural and artificial materials. Qualitative analysis gives an indication of the identity of the chemical species in the sample and quantitative analysis determines the amount of...
grades are also available.
Polarity and conductivity
AnhydrousAs a general term, a substance is said to be anhydrous if it contains no water. The way of achieving the anhydrous form differs from one substance to another...
is a very
polarIn chemistry, polarity refers to a separation of electric charge leading to a molecule or its chemical groups having an electric dipole or multipole moment. Polar molecules interact through dipole–dipole intermolecular forces and hydrogen bonds. Molecular polarity is dependent on the difference in...
liquid, having a
dielectric constantThe relative permittivity of a material under given conditions reflects the extent to which it concentrates electrostatic lines of flux. In technical terms, it is the ratio of the amount of electrical energy stored in a material by an applied voltage, relative to that stored in a vacuum...
of around 100. It has a high electrical conductivity, caused by dissociation through
protonatingIn chemistry, protonation is the addition of a proton to an atom, molecule, or ion. Some classic examples include*the protonation of water by sulfuric acid:*the protonation of isobutene in the formation of a carbocation:2C=CH2 + HBF4 → 3C+ + BF4−*the protonation of ammonia in the...
itself, a process known as
autoprotolysisIn autoprotolysis a proton is transferred between two identical molecules, one of which acts as a Brønsted acid, releasing a proton which is accepted by the other molecule acting as a Brønsted base. For example water undergoes autoprotolysis in the self-ionization of water reaction.Every solvent...
.
- 2 +
The
equilibrium constant for the autoprotolysis is
- Kap(25°C)= [][] = .
The comparable
equilibrium constant for waterThe self-ionization of water is the chemical reaction in which a proton is transferred from one water molecule to another, in pure water or an aqueous solution, to create the two ions, hydronium, H3O+ and hydroxide, OH−...
, K
w is 10
−14, a factor of 10
10 (10 billion) smaller.
In spite of the viscosity of the acid, the effective
conductivitiesMolar conductivity is defined as the conductivity of an electrolyte solution divided by the molar concentration of the electrolyte, and so measures the efficiency with which a given electrolyte conducts electricity in solution. Its units are siemens per meter per molarity, or siemens meter-squared...
of the and ions are high due to an intra-molecular proton-switch mechanism (analogous to the
Grotthuss mechanismThe Grotthuss mechanism is the mechanism by which an 'excess' proton or protonic defect diffuses through the hydrogen bond network of water molecules or other hydrogen-bonded liquids through the formation or cleavage of covalent bonds....
in water), making sulfuric acid a good conductor. It is also an excellent solvent for many reactions.
The
equilibriumIn a chemical reaction, chemical equilibrium is the state in which the concentrations of the reactants and products have not yet changed with time. It occurs only in reversible reactions, and not in irreversible reactions. Usually, this state results when the forward reaction proceeds at the same...
is actually more complex than shown above; 100% contains the following species at equilibrium (figures shown as millimoles per kilogram of solvent): (15.0), (11.3), (8.0), (4.4), (3.6), (0.1).
Reaction with water
The
hydration reactionIn organic chemistry, a hydration reaction is a chemical reaction in which a hydroxyl group and a hydrogen cation are added to the two carbon atoms bonded together in the carbon-carbon double bond which makes up an alkene functional group. The reaction usually runs in a strong acidic, aqueous...
of sulfuric acid is highly
exothermicAn exothermic reaction is a chemical reaction that releases energy in the form of light or heat. It is the opposite of an endothermic reaction. Expressed in a chemical equation:-Overview:...
. One should always add the acid to the water rather than the water to the acid. Because the reaction is in an equilibrium that favors the rapid protonation of water, addition of acid to the water ensures that the
acid is the limiting reagent. This reaction is best thought of as the formation of
hydroniumIn chemistry, a hydronium ion is the cation , a type of oxonium ion produced by protonation of water. This cation is often used to represent the nature of the proton in aqueous solution, where the proton is highly solvated...
ions:
- + → + HSO4− K1 = 2.4 x 106 (strong acid)
- HSO4− + → + SO42− K2 = 1.0 x 10−2
HSO
4- is the
bisulfate anion and SO
42- is the
sulfateIn inorganic chemistry, a sulfate is a salt of sulfuric acid.-Chemical properties:...
anion. K
1 and K
2 are the
acid dissociation constantAn acid dissociation constant, Ka, is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction known as dissociation in the context of acid-base reactions...
s. Because the hydration of sulfuric acid is thermodynamically favorable, sulfuric acid is an excellent dehydrating agent. The affinity of sulfuric acid for water is sufficiently strong that it will remove
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
and
oxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
atoms from other compounds; for example, mixing
starchStarch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
and concentrated sulfuric acid will give elemental
carbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
and water which is absorbed by the sulfuric acid (which becomes slightly diluted):
n → 6
n C + 6
n
The effect of this can be seen when concentrated sulfuric acid is spilled on paper; the cellulose reacts to give a
burntCombustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...
appearance, the
carbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
appears much as soot would in a fire. A more dramatic reaction occurs when sulfuric acid is added to a tablespoon of white
sugarSugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
in a
beakerA beaker is a simple container for stirring, mixing and heating liquids commonly used in many laboratories. Beakers are generally cylindrical in shape, with a flat bottom. Most also have a small spout to aid pouring as shown in the picture...
; a rigid column of black, porous carbon will quickly emerge.
The carbon will smell strongly of caramel due to the heat generated. Although less dramatic, the action of the acid on
cottonCotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
, even in diluted form, will destroy the fabric.
Other reactions
As an acid, sulfuric acid reacts with most
basesFor the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...
to give the corresponding sulfate. For example, the blue
copperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
salt
copper(II) sulfate, commonly used for
electroplatingElectroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal...
and as a
fungicideFungicides are chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality and profit. Fungicides are used both in agriculture and to fight fungal infections in animals...
, is prepared by the reaction of
copper(II) oxideCopper oxide or cupric oxide is the higher oxide of copper. As a mineral, it is known as tenorite.-Chemistry:It is a black solid with an ionic structure which melts above 1200 °C with some loss of oxygen...
with sulfuric acid:
- CuO (s) + (aq) → (aq) + (l)
Sulfuric acid can also be used to displace weaker acids from their salts. Reaction with
sodium acetateSodium acetate, CH3COONa, also abbreviated NaOAc, also sodium ethanoate, is the sodium salt of acetic acid. This colourless salt has a wide range of uses.-Industrial:...
, for example, displaces
acetic acidAcetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
, , and forms
sodium bisulfateSodium bisulfate, also known as sodium hydrogen sulfate , is an acid salt. It is a dry granular product that can be safely shipped and stored. The anhydrous form is hygroscopic. Solutions of sodium bisulfate are acidic, with a 1M solution having a pH of Sodium bisulfate, also known as sodium...
:
- + → +
Similarly, reacting sulfuric acid with
potassium nitratePotassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...
can be used to produce
nitric acidNitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
and a precipitate of potassium bisulfate. When combined with
nitric acidNitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
, sulfuric acid acts both as an acid and a dehydrating agent, forming the
nitronium ionThe nitronium ion, or sometimes the nitryl ion , , is a generally reactive cation created by the removal of an electron from the paramagnetic nitrogen dioxide molecule, or the protonation of nitric acid....
, which is important in
nitrationNitration is a general chemical process for the introduction of a nitro group into a chemical compound. The dominant application of nitration is for the production of nitrobenzene, the precursor to methylene diphenyl diisocyanate...
reactions involving
electrophilic aromatic substitutionElectrophilic aromatic substitution EAS is an organic reaction in which an atom, usually hydrogen, appended to an aromatic system is replaced by an electrophile...
. This type of reaction, where protonation occurs on an
oxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
atom, is important in many
organic chemistryOrganic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
reactions, such as
Fischer esterificationFischer esterification or Fischer–Speier esterification is a special type of esterification by refluxing a carboxylic acid and an alcohol in the presence of an acid catalyst. The reaction was first described by Emil Fischer and Arthur Speier in 1895. Most carboxylic acids are suitable for the...
and dehydration of alcohols.
Concentrated sulfuric acid reacts with
sodium chlorideSodium chloride, also known as salt, common salt, table salt or halite, is an inorganic compound with the formula NaCl. Sodium chloride is the salt most responsible for the salinity of the ocean and of the extracellular fluid of many multicellular organisms...
, and gives
hydrogen chlorideThe compound hydrogen chloride has the formula HCl. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity. Hydrogen chloride gas and hydrochloric acid are important in technology and industry...
gasGas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
and
sodium bisulfateSodium bisulfate, also known as sodium hydrogen sulfate , is an acid salt. It is a dry granular product that can be safely shipped and stored. The anhydrous form is hygroscopic. Solutions of sodium bisulfate are acidic, with a 1M solution having a pH of Sodium bisulfate, also known as sodium...
:
- NaCl + H2SO4 → NaHSO4 + HCl
As mentioned above, concentrated sulfuric acid is a powerful
dehydratingIn chemistry and the biological sciences, a dehydration reaction is usually defined as a chemical reaction that involves the loss of water from the reacting molecule. Dehydration reactions are a subset of elimination reactions...
agent, removing water from
sugarSugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
and other carbohydrates, to produce
carbonCarbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
, heat, steam, and a more dilute acid containing increased amounts of
hydroniumIn chemistry, a hydronium ion is the cation , a type of oxonium ion produced by protonation of water. This cation is often used to represent the nature of the proton in aqueous solution, where the proton is highly solvated...
and bisulfate ions.
n + Sulfuric acid → C
(graphitic foam) + steam + Sulfuric acid/water mixture
Sulfuric acid reacts with most metals via a single displacement reaction to produce
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
gas and the metal sulfate. Dilute attacks
ironIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
,
aluminiumAluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
,
zincZinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
,
manganeseManganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
,
magnesiumMagnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
and
nickelNickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
, but reactions with
tinTin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...
and
copperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
require the acid to be hot and concentrated.
LeadLead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
and
tungstenTungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
, however, are resistant to sulfuric acid. The reaction with iron shown below is typical for most of these metals, but the reaction with tin produces sulfur dioxide rather than hydrogen.
- Fe (s) + (aq) → (g) + (aq)
- Sn (s) + 2 (aq) → (aq) + 2 (l) + (g)
These reactions may be taken as typical: the hot concentrated acid generally acts as an oxidizing agent whereas the dilute acid acts a typical acid. Hence hot concentrated acid reacts with tin, zinc and copper to produce the salt, water and sulfur dioxide, whereas the dilute acid reacts with metals high in the reactivity series (such as Zn) to produce a salt and hydrogen. This is explained more fully in 'A New Certificate Chemistry' by Holderness and Lambert.
Benzene undergoes
electrophilic aromatic substitutionElectrophilic aromatic substitution EAS is an organic reaction in which an atom, usually hydrogen, appended to an aromatic system is replaced by an electrophile...
with sulfuric acid to give the corresponding
sulfonic acidSulfonic acid usually refers to a member of the class of organosulfur compounds with the general formula RS2–OH, where R is an alkyl or aryl. The formal part of acid, HS2–OH, are formally derivatives of the "parent" inorganic compound with the formula HSO2.-Preparation:Sulfonic acid is...
s:
Occurrence
Pure sulfuric acid is not encountered naturally on Earth in anhydrous form, due to its great
affinity for waterHygroscopy is the ability of a substance to attract and hold water molecules from the surrounding environment. This is achieved through either absorption or adsorption with the absorbing or adsorbing material becoming physically 'changed,' somewhat, by an increase in volume, stickiness, or other...
. Dilute sulfuric acid is a constituent of
acid rainAcid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions . It can have harmful effects on plants, aquatic animals, and infrastructure. Acid rain is caused by emissions of carbon dioxide, sulfur dioxide and nitrogen...
, which is formed by atmospheric
oxidationRedox reactions describe all chemical reactions in which atoms have their oxidation state changed....
of
sulfur dioxideSulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
in the presence of water – i.e., oxidation of
sulfurous acidSulfurous acid is the chemical compound with the formula H2SO3. There is no evidence that sulfurous acid exists in solution, but the molecule has been detected in the gas phase...
. 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 drainageAcid mine drainage , or acid rock drainage , refers to the outflow of acidic water from metal mines or coal mines. However, other areas where the earth has been disturbed may also contribute acid rock drainage to the environment...
(AMD) or acid rock drainage (ARD). This acidic water is capable of dissolving metals present in sulfide ores, which results in brightly colored, toxic streams. The oxidation of
pyriteThe mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
(iron sulfide) by molecular oxygen produces iron(II), or :
- 2 (s) + 7 + 2 → 2 (aq) + 4 (aq) + 4
The can be further oxidized to :
- 4 + + 4 → 4 + 2
The produced can be precipitated as the
hydroxideHydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...
or
hydrous oxideHydrous ferric oxides, also called hydrous iron oxides, are a class of minerals that form from the weathering of minerals that contain iron and hydroxides , and weakly bound water. They are poorly crystalline, highly porous and have large surface areas...
:
- (aq) + 3 → (s) + 3
The iron(III) ion ("ferric iron") can also oxidize pyrite:
- (s) + 14 + 8 → 15 (aq) + 2 (aq) + 16
When iron(III) oxidation of pyrite occurs, the process can become rapid.
pHIn chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
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 neutralizing capacityAcid-neutralizing capacity or ANC in short is a measure for the overall buffering capacity against acidification for a solution, e.g. surface water or soil water....
(ANC) of the aquifer can neutralize the produced acid. In such cases, the
total dissolved solidsTotal Dissolved Solids is a measure of the combined content of all inorganic and organic substances contained in a liquid in: molecular, ionized or micro-granular suspended form. Generally the operational definition is that the solids must be small enough to survive filtration through a sieve...
(TDS) concentration of the water can be increased from the dissolution of minerals from the acid-neutralization reaction with the minerals.
Sulfuric acid is used as a defence by certain marine species, for example, the phaeophyte alga
Desmarestia munda (order
DesmarestialesDesmarestiales is an order in the brown algae . Member of this order have terete or ligulate pinnately branched thalli attached by discoid holdfasts. They have a sporphytic thallus usually aggregated to form a pseudo parenchyma...
) concentrates sulfuric acid in cell vacuoles.
Venus
Sulfuric acid is produced in the upper atmosphere of
VenusVenus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
by the
SunThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
's
photochemicalPhotochemistry, a sub-discipline of chemistry, is the study of chemical reactions that proceed with the absorption of light by atoms or molecules.. Everyday examples include photosynthesis, the degradation of plastics and the formation of vitamin D with sunlight.-Principles:Light is a type of...
action on
carbon dioxideCarbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
,
sulfur dioxideSulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
, and
waterWater is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
vapor.
UltravioletUltraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
photonIn physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s of wavelengths less than 169
nmA nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter...
can
photodissociatePhotodissociation, photolysis, or photodecomposition is a chemical reaction in which a chemical compound is broken down by photons. It is defined as the interaction of one or more photons with one target molecule....
carbon dioxide into
carbon monoxideCarbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
and atomic
oxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
. Atomic oxygen is highly reactive. When it reacts with sulfur dioxide, a trace component of the Venusian atmosphere, the result is
sulfur trioxideSulfur trioxide is the chemical compound with the formula SO3. In the gaseous form, this species is a significant pollutant, being the primary agent in acid rain. It is prepared on massive scales as a precursor to sulfuric acid.-Structure and bonding:Gaseous SO3 is a trigonal planar molecule of...
, which can combine with water vapor, another trace component of Venus's atmosphere, to yield sulfuric acid. 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 km and as high as 90 km above the surface. The permanent Venusian clouds produce a concentrated acid rain, as the clouds in the atmosphere of Earth produce water rain.
The atmosphere exhibits a sulfuric acid cycle. As sulfuric acid rain droplets fall down through the hotter layers of the atmosphere's temperature gradient, they are heated up and release water vapor, becoming more and more concentrated. When they reach temperatures above 300°C, sulfuric acid begins to decompose into sulfur trioxide and water, both in the gas phase. Sulfur trioxide is highly reactive and dissociates into sulfur dioxide and atomic oxygen, which oxidizes traces of carbon monoxide to form carbon dioxide. Sulfur dioxide and water vapor rise on convection currents from the mid-level atmospheric layers to higher altitudes, where they will be transformed again into sulfuric acid, and the cycle repeats.
Europa
Infrared spectra from
NASAThe National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Galileo mission show distinct absorptions on
JupiterJupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
's moon
EuropaEuropa Slightly smaller than Earth's Moon, Europa is primarily made of silicate rock and probably has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Its surface is composed of ice and is one of the smoothest in the Solar System. This surface is striated by cracks and...
that have been attributed to one or more sulfuric acid hydrates. Sulfuric acid in solution with water causes significant
freezing-point depressionFreezing-point depression describes the phenomenon in which the freezing point of a liquid is depressed when another compound is added, meaning that a solution has a lower freezing point than a pure solvent. This happens whenever a non-volatile solute is added to a pure solvent, such as water...
of water's
melting pointThe melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...
, down to 210 kelvin (-63.2 °C), and this would make more likely the existence of liquid solutions beneath Europa's icy crust.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.
Manufacture
Sulfuric acid is produced from
sulfurSulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
, oxygen and water via the conventional
contact processThe contact process is the current method of producing sulphuric acid in the high concentrations needed for industrial processes. Platinum was formerly employed as a catalyst for the reaction, but as it is susceptible to poisoning by arsenic impurities in the sulfur feedstock, vanadium oxide is...
(DCDA) or the
wet sulfuric acid processThe wet sulfuric acid process is one of the key gas desulfurization processes on the market today. Since the Danish catalyst company Haldor Topsoe introduced and patented this technology in the late 1980s, it has been recognised as an efficient process for recovering sulfur from various process...
(WSA).
Contact process (DCDA)
In the first step, sulfur is burned to produce sulfur dioxide.
- S (s) + (g) → (g)
This is then oxidized to sulfur trioxide using oxygen in the presence of a
vanadium(V) oxideVanadium oxide is the chemical compound with the formula V2O5. Commonly known as vanadium pentoxide, this brown/yellow solid is the most stable and common compound of vanadium. Upon heating it reversibly loses oxygen...
catalyst. This reaction is reversible and the formation of the sulfur trioxide is exothermic.
- 2 (g) + (g) 2 (g) (in presence of )
The sulfur trioxide is absorbed into 97–98% to form
oleumOleum , or fuming sulfuric acid refers to a solution of various compositions of sulfur trioxide in sulfuric acid or sometimes more specifically to disulfuric acid ....
, also known as fuming sulfuric acid. The oleum is then diluted with water to form concentrated sulfuric acid.
- (l) + → (l)
- (l) + (l) → 2 (l)
Note that directly dissolving in water is not practical due to the highly
exothermicAn exothermic reaction is a chemical reaction that releases energy in the form of light or heat. It is the opposite of an endothermic reaction. Expressed in a chemical equation:-Overview:...
nature of the
reactionA chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...
between sulfur trioxide and water. The reaction forms a corrosive aerosol that is very difficult to separate, instead of a liquid.
- (g) + (l) → (l)
Wet sulfuric acid process (WSA)
In the first step, sulfur is burned to produce sulfur dioxide:
- S(s) + (g) → (g)
or, alternatively,
hydrogen sulfideHydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
gas is incinerated to gas:
- 2 + 3 → 2 + 2 (−518 kJ/mol)
This is then oxidized to sulfur trioxide using oxygen with
vanadium(V) oxideVanadium oxide is the chemical compound with the formula V2O5. Commonly known as vanadium pentoxide, this brown/yellow solid is the most stable and common compound of vanadium. Upon heating it reversibly loses oxygen...
as catalyst.
- 2 + → 2 (−99 kJ/mol) (reaction is reversible)
The sulfur trioxide is hydrated into sulfuric acid :
- + → (g) (−101 kJ/mol)
The last step is the condensation of the sulfuric acid to liquid 97–98% :
- (g) → (l) (−69 kJ/mol)
Other methods
Another method is the less well-known metabisulfite method, in which metabisulfite is placed at the bottom of a beaker, and 12.6 molar concentration hydrochloric acid is added. The resulting gas is bubbled through nitric acid, which will release brown/red vapors. The completion of the reaction is indicated by the ceasing of the fumes. This method does not produce an inseparable mist, which is quite convenient.
Sulfuric acid can be produced in the laboratory by burning sulfur in air and dissolving the gas produced in a hydrogen peroxide solution.
- SO2 + H2O2 → H2SO4
Prior to 1900, most sulfuric acid was manufactured by the
lead chamber processThe lead chamber process was an industrial method used to produce sulfuric acid in large quantities. It has been largely supplanted by the contact process....
. As late as 1940, up to 50% of sulfuric acid manufactured in the United States was produced by chamber process plants.
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. World production in 2001 was 150 million
tonThe ton is a unit of measure. It has a long history and has acquired a number of meanings and uses over the years. It is used principally as a unit of weight, and as a unit of volume. It can also be used as a measure of energy, for truck classification, or as a colloquial term.It is derived from...
s, with an approximate value of US$8 billion. The major use (60% of total production worldwide) for sulfuric acid is in the "wet method" for the production of
phosphoric acidPhosphoric acid, also known as orthophosphoric acid or phosphoric acid, is a mineral acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way...
, used for manufacture of
phosphateA phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
fertilizerFertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
s as well as
trisodium phosphateTrisodium phosphate is a cleaning agent, food additive, stain remover and degreaser. It is a white, granular or crystalline solid, highly soluble in water producing an alkaline solution....
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
fluorapatiteFluorapatite, often with the alternate spelling of fluoroapatite, is a mineral with the formula Ca53F . Fluorapatite is a hard crystalline solid. Although samples can have various color , the pure mineral is colorless as expected for a material lacking transition metals...
, though the exact composition may vary. This is treated with 93% sulfuric acid to produce
calcium sulfateCalcium sulfate is a common laboratory and industrial chemical. In the form of γ-anhydrite , it is used as a desiccant. It is also used as a coagulant in products like tofu. In the natural state, unrefined calcium sulfate is a translucent, crystalline white rock...
,
hydrogen fluorideHydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the...
(HF) and
phosphoric acidPhosphoric acid, also known as orthophosphoric acid or phosphoric acid, is a mineral acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way...
. The HF is removed as
hydrofluoric acidHydrofluoric acid is a solution of hydrogen fluoride in water. It is a valued source of fluorine and is the precursor to numerous pharmaceuticals such as fluoxetine and diverse materials such as PTFE ....
. The overall process can be represented as:
- + 5 + 10 → 5 + HF + 3
Sulfuric acid is used in large quantities by the
ironIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
and
steelSteel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
making industry to remove oxidation,
rustRust is a general term for a series of iron oxides. In colloquial usage, the term is applied to red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture...
and scale from rolled sheet and billets prior to sale to the
automobileAn automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
and major appliances 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 and sulfur trioxide 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 sulfateAmmonium sulfate , 2SO4, is an inorganic salt with a number of commercial uses. The most common use is as a soil fertilizer. It contains 21% nitrogen as ammonium cations, and 24% sulfur as sulfate anions...
, an important nitrogen fertilizer, is most commonly produced as a byproduct from
coking plantsCoke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...
supplying the iron and steel making plants. Reacting the
ammoniaAmmonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
produced in the thermal decomposition of
coalCoal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
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 aluminum sulfate, also known as paper maker's alum. This can react with small amounts of soap on paper pulp fibers to give gelatinous aluminum carboxylates, which help to coagulate the pulp fibers into a hard paper surface. It is also used for making aluminum hydroxide, which is used at
water treatmentWater treatment describes those processes used to make water more acceptable for a desired end-use. These can include use as drinking water, industrial processes, medical and many other uses. The goal of all water treatment process is to remove existing contaminants in the water, or reduce the...
plants to
filterA water filter removes impurities from water by means of a fine physical barrier, a chemical process or a biological process. Filters cleanse water to various extents for irrigation, drinking water, aquariums, and swimming pools.-Methods of filtration:...
out impurities, as well as to improve the taste of the
waterWater is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
. Aluminum sulfate is made by reacting
bauxiteBauxite is an aluminium ore and is the main source of aluminium. This form of rock consists mostly of the minerals gibbsite Al3, boehmite γ-AlO, and diaspore α-AlO, in a mixture with the two iron oxides goethite and hematite, the clay mineral kaolinite, and small amounts of anatase TiO2...
with sulfuric acid:
- + 3 → + 3
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
cyclohexanone oximeThis page was incorrectly redirected to Caprolactam .Cyclohexanone oxime is a different compound; both have the empirical formula C6H11NO, but are structural isomers of each other....
to
caprolactamCaprolactam is an organic compound with the formula 5CNH. This colourless solid is a lactam or a cyclic amide of caproic acid. Approximately 2 billion kilograms are produced annually...
, used for making
nylonNylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...
. It is used for making
hydrochloric acidHydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
from
saltIn chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...
via the
Mannheim processThe Mannheim process is an important method for the manufacture of hydrogen chloride and sodium sulfate from sodium chloride and sulfuric acid in which case the Na2SO4 is known as salt cake:2 NaCl + H2SO4 → Na2SO4 + 2 HCl...
. Much is used in
petroleumPetroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
refining, for example as a catalyst for the reaction of
isobutaneIsobutane, also known as methylpropane, is an isomer of butane. It is the simplest alkane with a tertiary carbon. Concerns with depletion of the ozone layer by freon gases have led to increased use of isobutane as a gas for refrigeration systems, especially in domestic refrigerators and freezers,...
with
isobutyleneIsobutylene is a hydrocarbon of significant industrial importance. It is a four-carbon branched alkene , one of the four isomers of butylene. At standard temperature and pressure it is a colorless flammable gas.-Uses:...
to give isooctane, a compound that raises the
octane ratingOctane rating or octane number is a standard measure of the anti-knock properties of a motor or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating...
of
gasolineGasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
(petrol). Sulfuric acid is also important in the manufacture of
dyeA dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution, and requires a mordant to improve the fastness of the dye on the fiber....
stuffs 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
sulfur-iodine cycleThe sulfur–iodine cycle is a three-step thermochemical cycle used to produce hydrogen.The S–I cycle consists of three chemical reactions whose net reactant is water and whose net products are hydrogen and oxygen. All other chemicals are recycled...
is a series of thermo-chemical processes used to obtain
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
. It consists of three chemical reactions whose net reactant is
waterWater is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
and whose net products are hydrogen and
oxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
.
| 2 → 2 + 2 + |
|
(830 °C) |
| + + 2 → 2 HI + |
|
(120 °C) |
| 2 HI → + |
|
(320 °C) |
The sulfur and
iodineIodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
compounds are recovered and reused, hence the consideration of the process as a cycle. This process is
endothermicIn thermodynamics, the word endothermic describes a process or reaction in which the system absorbs energy from the surroundings in the form of heat. Its etymology stems from the prefix endo- and the Greek word thermasi,...
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 economyThe hydrogen economy is a proposed system of delivering energy using hydrogen. The term hydrogen economy was coined by John Bockris during a talk he gave in 1970 at General Motors Technical Center....
. It does not require hydrocarbons like current methods of
steam reformingFossil fuel reforming is a method of producing hydrogen or other useful products from fossil fuels such as natural gas. This is achieved in a processing device called a reformer which reacts steam at high temperature with the fossil fuel. The steam methane reformer is widely used in industry to...
. But note that all of the available energy in the hydrogen so produced is supplied by the heat used to make it.
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 a large scale.
Laboratory hazards
The corrosive properties of sulfuric acid are accentuated by its highly
exothermic reactionAn exothermic reaction is a chemical reaction that releases energy in the form of light or heat. It is the opposite of an endothermic reaction. Expressed in a chemical equation:-Overview:...
with water. Burns from sulfuric acid are potentially more serious than those of comparable strong acids (e.g.
hydrochloric acidHydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
), as there is additional tissue damage due to dehydration and particularly secondary thermal damage due to the heat liberated by the reaction with water.
The danger is greater with more concentrated preparations of sulfuric acid, but even the normal laboratory "dilute" grade (approximately 1 M, 10%) will char paper by dehydration if left in contact for a sufficient time. Therefore, solutions equal to or stronger than 1.5 M are labeled "CORROSIVE", while solutions greater than 0.5 M but less than 1.5 M are labeled "IRRITANT".
The standard first aid treatment for acid spills on the skin is, as for other
corrosiveCorrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...
agents, irrigation with large quantities of water. Washing is continued for at least ten to fifteen minutes to cool the tissue surrounding the acid burn and to prevent secondary damage. Contaminated clothing is 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. The concentrated acid is always added to water and not the other way around, to take advantage of the relatively high
heat capacityHeat capacity , or thermal capacity, is the measurable physical quantity that characterizes the amount of heat required to change a substance's temperature by a given amount...
of water. Addition of water to concentrated sulfuric acid leads to the dispersal of a sulfuric acid
aerosolTechnically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...
or worse, an
explosionAn explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. An explosion creates a shock wave. If the shock wave is a supersonic detonation, then the source of the blast is called a "high explosive"...
. Preparation of solutions greater than 6 M (35%) in concentration is most dangerous, as the heat produced may be sufficient to boil the diluted acid: efficient mechanical stirring and external cooling (such as an ice bath) are essential.
On a laboratory scale, sulfuric acid can be diluted by pouring concentrated acid onto crushed ice made from de-ionized water. The ice melts in an endothermic process while dissolving the acid. The amount of heat needed to melt the ice in this process is greater than the amount of heat evolved by dissolving the acid so the solution remains cold. After all the ice has melted, further dilution can take place using water.
Pure sulfuric acid may be safely stored in glass vessels or bottles.
Industrial hazards
Although sulfuric acid is non-flammable, contact with metals in the event of a spillage can lead to the liberation of
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
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 edemaPulmonary edema , or oedema , is fluid accumulation in the air spaces and parenchyma of the lungs. It leads to impaired gas exchange and may cause respiratory failure...
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 tractIn humans the respiratory tract is the part of the anatomy involved with the process of respiration.The respiratory tract is divided into 3 segments:*Upper respiratory tract: nose and nasal passages, paranasal sinuses, and throat or pharynx...
are inconclusive as of 1997. In the United States, the
permissible exposure limitThe permissible exposure limit is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent. For chemicals, the chemical regulation is usually expressed in parts per million , or sometimes in milligrams per cubic metre . Units of measure for physical...
(PEL) for sulfuric acid is fixed at 1 mg/m
3: limits in other countries are similar. There have been reports of sulfuric acid ingestion leading to
vitamin B12 deficiencyVitamin B12 deficiency or hypocobalaminemia is a low blood level of vitamin B12, it can cause permanent damage to nervous tissue as a long term effect. Vitamin B12 was discovered from its relationship to the disease pernicious anemia, which is an autoimmune disease that destroys parietal cells in...
with subacute combined degeneration. The spinal cord is most often affected in such cases, but the optic nerves may show demyelination, loss of
axonAn axon is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma....
s and
gliosisGliosis is a proliferation of astrocytes in damaged areas of the central nervous system . This proliferation usually leads to the formation of a glial scar....
.
Legal restrictions
International commerce of sulfuric acid is controlled under the
United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances, 1988The United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances of 1988 is one of three major drug control treaties currently in force. It provides additional legal mechanisms for enforcing the 1961 Single Convention on Narcotic Drugs and the 1971 Convention on...
, 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 US sulfuric acid is included in List II of the
list of essential or precursor chemicalsThe United States Drug Enforcement Administration maintains lists regarding not only the classification of illicit drugs . It also maintains List I of chemicals and List II of chemicals, which contain chemicals which are used to manufacture the controlled substances/illicit drugs...
established pursuant to the
Chemical Diversion and Trafficking ActThe Chemical Diversion and Trafficking Act of 1988 was an amendment to the Controlled Substances Act to regulate precursor chemicals, essential chemicals, tableting machines, and encapsulating machines by imposing record keeping and import/export reporting requirements on transactions involving...
. 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 AdministrationThe Drug Enforcement Administration is a federal law enforcement agency under the United States Department of Justice, tasked with combating drug smuggling and use within the United States...
.
Further reading
- A New Certificate Chemistry by A Holderness and J Lambert, Heinemann 1976.
- 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.
External links