Sulphuric Acid

Sulfuric acid (alternative spelling sulphuric acid) is a highly corrosive strong mineral acid with the molecular formula H2SO4 and molecular weight 98.079 g/mol. It is a pungent-ethereal, colorless to slightly yellow viscous liquid that is soluble in water at all concentrations. Sometimes, it is dyed dark brown during production to alert people to its hazards. The historical name of this acid is oil of vitriol.

Sulfuric acid is a diprotic acid and shows different properties depending upon its concentration. Its corrosiveness on other materials, like metals, living tissues or even stones, can be mainly ascribed to its strong acidic nature and, if concentrated, strong dehydrating and oxidizing properties. Sulfuric acid at a high concentration can cause very serious damage upon contact, since not only does it cause chemical burns via hydrolysis, but also secondary thermal burns through dehydration. It can lead to permanent blindness if splashed onto eyes and irreversible damage if swallowed. Accordingly, safety precautions should be strictly observed when handling it. Moreover, it is hygroscopic, readily absorbing water vapour from the air.

Sulfuric acid has a wide range of applications including in domestic acidic drain cleaners, as an electrolyte in lead-acid batteries and in various cleaning agents. It is also a central substance in the chemical industry. Principal uses include mineral processing, fertilizer manufacturing, oil refining, wastewater processing, and chemical synthesis. It is widely produced with different methods, such as contact process, wet sulfuric acid process, lead chamber process and some other methods.

Sulfuric acid is also a key substance in the chemical industry . It is must commonly used in fertilizer manufacture , but is also important in mineral processing , oil refining , wastewater in mineral processing , and chemical synthesis . It has a wide range of end applications including in domestic acidic drain cleaners , in dehydrating a compound , and in various cleaning agents .

Physical properties

Grades of sulfuric acid
Although nearly 100 % sulfuric acid solutions can be made , the subsequent loss of SO3 at the boiling point brings the concentration to 98.3% acid . The 98.3% 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 .” Chamber acid ” and “tower acid ” were the two concentrations of sulfuric acid produced by the lead chamber process , chember acid being the acid produced in the lead chamber itself ( < 70 % to avoid contamination with nitrosylsulfuric acid ) and tower acid being the acid recovered from thr 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 , ” 10 M ” sulfuric acid ( the modern equivalent of chember acid , used in many titrations ) 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 deg. C (176 deg . F ) or higher .

Pure sulfuric acid has a vaper pressure of < 0.001 mmHg at 25 deg . C mmHgat 145.8 Deg. C and 98 % sulfuric acid has a < 1 mmHg vapor pressure at 40 deg . C .

Pure sulfuric acid as sold in liquied , like oil , and this explains the old name of the acid ( oil of vitriol ) .

Polarity and conductivity

Equilibrium of anhydrous sulfuric acid

Species mMol/kg
HSO4- 15.0
H3SO4+ 11.3
H3O+ 8.0
HS2O7 4.4
H2S2O7 3.6
H2O 0.1

Similarly , mixing starch into concentrated sulfuric acid will give elemental carbon and water as absorbed by the sulfuric acid ( which becomes slightly diluted ) . The effect of this can be seen when concentraded sulfuric acid is spilled on paper which is composed of cellulose , the cellulose reacts to give a burnt appearance , the carbon appears much as soot would in a fire . Altough less dramatic , the action of the acid on cotton , even in diluted form , will destroy the fabric .
on cotton, even in diluted form, will destroy the fabric.

The reaction with copper(II) sulfate can also demonstrate the dehydration property of sulfuric acid. The blue crystal is changed into white powder as water is removed.

As an acid, sulfuric acid reacts with most bases to give the corresponding sulfate. For example, the blue copper salt copper(II) sulfate, commonly used for electroplating and as a fungicide, is prepared by the reaction of copper(II) oxide with sulfuric acid:

Cuo (s) + H2SO4 (aq) -CuSO4 (aq) + H2O(I)
Sulfuric acid can also be used to displace weaker acids from their salts. Reaction with sodium acetate, for example, displaces acetic acid, CH3COOH
and forms sodium bisulfate:

The above reaction is thermodynamically favored due to the high bond enthalpy of the Si- F bond in the Side product , Protonation using simply HF/SbF, however , have met with failure , as pure sulfuric acid undergoes self – ionization to give {h3so4 } + by the HF/SbF system .

Reactions with non-metals

Hot concentrated sulfuric acid oxidizes non – metals such as carbon ( as bituminous coal ) and sulfar .

C + 2 H2SO4 – CO2 + 2SO2 + 2H2O
S + 2H2SO4 – 3SO2 + 2H2O


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 the year 2004 was about 180 million tonnes with the following geographic distribution: Asia 35%, North America (including Mexico) 24%, Africa 11%, Western Europe 10%, Eastern Europe and Russia 10%, Australia and Oceania 7%, South America 7 % Most of this amount (≈60%) is consumed for fertilizers, particularly superphosphates, ammonium phosphate and ammonium sulfates. About 20% is used in chemical industry for production of detergents, synthetic resins, dyestuffs, pharmaceuticals, petroleum catalysts, insecticides and antifreeze as well as in various processes such as oil well acidicizing, aluminium reduction, paper sizing, water treatment. About 6% of uses are related to pigments and include paints , enamels , printing inks, coated fabrics and paper, and the rest is dispersed into a multitude of applications such as production of explosives,
cellophane , acetate and viscose textiles , lubricants , non – ferrous metals , and batteries .

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.

Industrial hazards
Sulfuric acid is non-flammable.

The main occupational risks posed by this acid 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 adema 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. Repeated occupational exposure to sulfuric acid mists may increase the chance of lung cancer by up to 64 % .

Leave a Reply

Your email address will not be published. Required fields are marked *