Sulfuric Acid
WHAT IS SULFURIC ACID?
Sulfuric acid or sulfur essence is one of the strongest and most important mineral acids that has wide applications in the chemical industry. This acid has the chemical formula H2SO4H 2SO4 and dissolves in water in any ratio. Sulfuric acid is a colorless and odorless liquid, with high viscosity and high corrosive properties, which is used in the production of fertilizers, refining oil, making pigments and organic and inorganic chemicals.
BASIC INFORMATION ABOUT SULFURIC ACID
Sulfuric acid (hydrogen sulfate or sulfur ink), also known as “oil of vitriol”, is a mineral acid that is composed of the elements sulfur, oxygen, and hydrogen. Its chemical formula is written as H2SO4. Sulfuric acid is a colorless, odorless and viscous liquid that is soluble in water and is synthesized through reactions that are very exothermic.
The corrosive property of this acid compared to other materials can be attributed to its strong acidic property; And if it is present in high concentration, besides its oxidizing properties, it also absorbs water. This material is also moisture absorbent and easily absorbs water vapor from the air. As a result of contact with living tissue, sulfuric acid can cause severe chemical burns and even secondary burns due to dehydration. Even in low concentrations it is very dangerous!
Industrial sulfuric acid is a very important chemical. The production of this material in a country is a good indicator to determine the ability of that country’s industries. This substance is a main ingredient in the chemical industry. This substance is usually used in the manufacture of agricultural fertilizers, but it is also used in the processing of minerals, oil refining, wastewater treatment and the synthesis of many chemical compounds.
A wide range of applications of sulfuric acid is its use in the production of cleaning solutions for scaling and draining domestic sewage. This acid is also used as an electrolyte in lead-acid batteries, in dehydrating a compound, etc. Other applications of this acid will be discussed later.
A LOOK AT THE HISTORY OF SULFURIC ACID (HYDROGEN SULFATE)
To know everything about hydrogen sulfate, it is better to get acquainted with the history of this substance. The study of vitriol, a group of glassy-looking minerals from which acid can be obtained, began in ancient times. The Sumerians had a list of types of vitriol that they classified by color. Some early reports on the origin and properties of vitriol are found in the works of the Greek physician Dioscorides (1st century AD). Galen also discussed its medicinal use. Alchemists of the Islamic world during the Middle Ages, Jaber bin Hayyan (721-815 AD), Muhammad bin Zakariya Razi (865-925 AD), included vitriol in their mineral classification list. Avicenna focused on medical applications and various types of vitriol. Razi is the first person to produce sulfuric acid.
In the 17th century, Johann Glauber, a German-Dutch chemist, prepared this substance by burning sulfur with potassium nitrate salt, KNO3, in the presence of steam. With the decomposition of potassium nitrate salt, sulfur is oxidized to SO3, which is produced by combining with water, hydrogen sulfate. In 1736, Joshua Ward, an apothecary from London, started the first production of concentrated hydrogen sulfate using this method. In 1746 in Birmingham, “John Roebuck” presented this method to produce hydrogen sulfate in resistant lead chambers. These containers were sturdier, cheaper, and could even be larger than the glass containers used in previous methods. This process allows the industrial production of sulfuric acid. After several refinements, this method, called the lead chamber process or “chamber process,” was used for nearly two centuries in the production of standard hydrogen sulfate. Sulfuric acid produced by John Roebuck’s process was closer to 65% concentration. Later improvements in the lead chamber process by the French chemist Joseph Louis Guilsac and the English chemist Glover improved the concentration of the acid by about 78%. However, the production of some dyes and other chemical processes requires a more concentrated product of sulfuric acid. In 1831, British vinegar merchant Peregrine Phillips patented a contact process for the production of sulfuric acid, a much more economical process for producing sulfur trioxide and “concentrated sulfuric acid”. Today, almost all hydrogen sulfate in the world is produced using this method.
SULFURIC ACID PRODUCTION METHODS
Sulfuric acid is produced from sulfur, oxygen and water through the conventional contact process (DCDA) or the wet process (WSA).
1- H2SO4 production method through contact process: In the first stage, sulfur burns to produce sulfur dioxide:
S+O2 → SO2
Sulfur dioxide is converted to sulfur trioxide by oxygen in the presence of vanadium (V) oxide catalyst. This reaction is reversible and the formation of sulfur trioxide is exothermic. 2SO2 + O2
2SO2 + O2 ⇌2SO3
Sulfur trioxide is absorbed into 97-98% H2SO4 to produce the compound oleum (H2S2O7). It is also known as fumigant hydrogen sulfate. Oleum is then diluted with water and concentrated hydrogen sulfate is formed.
H2SO4+SO3 → H2S2O7
H2S2O7 + H2oO → 2H2SO4
2- Sulfuric acid production method in wet process: In the first step, sulfur is burned to produce sulfur dioxide:
S+O2→SO2
Or, gaseous hydrogen sulfide (H2S) is burned to gaseous SO2:
2H2S+3O2 → 2H2O+2SO2 (-518 kj/mol)
Sulfur dioxide is then oxidized to sulfur trioxide using oxygen with vanadium (V) oxide as a catalyst:
2SO2+O2 ⇌ 2SO3 (-99 kj/mol)
(reaction is reversible)
Sulfur trioxide is converted into hydrated sulfuric acid:
SO3+H2O → H2SO4 (g) (-101 kj/mol)
The last step is the condensation of sulfuric acid to 97-98% liquid:
H2SO4 (g) → H2SO4 (l) (-69 kj/mol)
3- Other methods to produce hydrogen sulfate: These methods are implemented in a laboratory:
- Reaction of sulfuric acid, nitric acid and water:
3SO2 + 2HNO3 + 2H2O → 3H2SO4 + 2NO
- Hydrogen sulfate can be produced in the laboratory by burning sulfur in air and then dissolving the resulting sulfur dioxide in hydrogen peroxide solution:
SO2 + H2O2 → H2SO4
- Another method is to dissolve sulfur dioxide in an aqueous solution of an oxidizing metal salt such as copper (II) or iron (III) chloride:
2FeCl3 + 2H2O + SO2 → 2FeCl2 + H2SO4 + 2HCl
2CuCl2 + 2H2O + SO2 → 2CuCl + H2SO4 + 2HCl
PROPERTIES AND APPLICATIONS OF SULFURIC ACID
1- Reaction of sulfuric acid with water: Since the hydration reaction of this acid is very exothermic, dilution should always be done by adding acid to water, not water to acid. In this reaction, hydronium ions are formed:
-H2SO4+H2O → H3O+ + HSO4
–HSO4– + H2O → H3O+ + SO42
Also, since the hydration of this acid is thermodynamically favorable and its desire to combine with water is strong enough, hydrogen sulfate is considered an excellent drying agent.
Concentrated hydrogen sulfate has a very strong effect and removes water from other chemical compounds, including sugars and other carbohydrates, and during that process, carbon, heat, and steam are produced.
2- Properties of acid and base: As an acid, it reacts with most bases to produce the sulfate salt. For example, copper(II) sulfate, the copper salt commonly used for electroplating, is prepared by reacting copper(II) oxide with sulfuric acid:
CuO (s) + H2SO4 (aq) → CuSO4 (aq) + H2O (I)
Hydrogen sulfate can also be used to exchange weaker acids from their salts. For example, reaction with sodium acetate exchanges acetic acid to form sodium sulfate:
N2SO4 + CH3COONa → NaHSO4 + CH3COOH
Likewise, the reaction of hydrogen sulfate with potassium nitrate can be used to produce nitric acid and precipitate potassium bisulfate. When the acid combines with nitric acid, it acts as both an acid and a water reducing agent, forming the nitronium ion.
3- Reaction with metals: Even dilute hydrogen sulfate reacts with many metals through a displacement reaction—like other common acids—to produce hydrogen gas and a salt (metal sulfate). These reactive metals (metals higher than copper in the chemical reaction series) are iron, aluminum, zinc, manganese, magnesium, and nickel.
Fe + H2SO4 → H2 + FeSO4
Concentrated hydrogen sulfate acts as an oxidizing agent and sulfur dioxide is released in the reaction:
+ Cu + 2H2SO4 → SO2 + 2H2O + SO42- + Cu2
Lead and tungsten are resistant to sulfuric acid.
4- Reaction of sulfuric acid with carbon: Concentrated and hot hydrogen sulfate oxidizes carbon and sulfur.
C + 2H2SO4 → CO2 + 2SO2 + 2H2O
S + 2H2SO4 → 3SO2 + 2H2O
5- Reaction with sodium chloride: This substance reacts with sodium chloride and hydrogen chloride gas and sodium sulfate are produced:
NaCl + H2SO4 → NaHSO4 + HCl
GRADES OF SULFURIC ACID
Although an almost 100% solution of hydrogen sulfate can be produced, after that, at the boiling point, the SO3 is destroyed, bringing the acid concentration to 98.3%.
The 98.3% acid grade is more stable for storage and the more common form is what is described as “concentrated sulfuric acid”.
Other concentrations of industrial and edible sulfuric acid are used for different purposes. Some common concentrations are:
| NO | Common Name | Concentration (mol/L) | Density (kg/L) | Mass Segregation h2SO4 |
|---|---|---|---|---|
| 1 | Dilute Sulfuric Acid | 4.2> | 1.00-1.25 | 29%> |
| 2 | Battery Acid Application (in lead-acid batteries) | 5.2-4.2 | 1.28-1.25 | 32% -29 |
| 3 | Chamber acid | 11.5-9.6 | 1.60-1.52 | 70%-62 |
| 4 | Fertilizer acid | 11.5-9.6 | 1.60-1.52 | 70%-62 |
| 5 | Tower acid | 14.0-13.5 | 1.73-1.70 | 80%-78 |
| 6 | Glover acid | 14.0-13.5 | 1.73-1.70 | 80%-78 |
| 7 | Be' (''66-degree baume') acid 66' | 17.4 | 1.83 | 93.2% |
| 8 | Concentrated Sulfuric acid | 18.4 | 1.84 | 98.3% |
APPLICATIONS OF SULFUR INK
- This substance is a very important industrial chemical. The largest amount (about 60%) of this acid is used for agricultural fertilizers, especially superphosphates, ammonium phosphates and ammonium sulfates.
- About 20% of the volume of acid produced in the world is used in the chemical industry for the production of detergents, synthetic resins, dyes, pharmaceuticals, petroleum catalysts, insecticides and antifreeze.
- Hydrogen sulfate is also used in various processes such as acidification of oil wells, aluminum reduction process, paper sizing, water treatment, etc.
- About 6% of the uses of this acid are related to the pigment production industry, which includes paint, glaze, printing ink, and textile dyeing.
- Other industrial uses of sulfuric acid include the production of explosives, acetate and viscose fibers, lubricants, ferrous metals and batteries.
1- The use of industrial hydrogen sulfate in the production of chemicals
The most common use of sulfuric acid is in the “wet method” to produce phosphoric acid, which is used to produce phosphate fertilizers. In this method, phosphate rock is used (more than 100 million tons are processed annually).
This is treated with 93% sulfuric acid to produce calcium sulfate, hydrogen fluoride (HF) and phosphoric acid. HF is eliminated as hydrofluoric acid in the reaction. The general reaction can be shown as follows:
Ca5F(PO4)3 + 5H2SO4 + 10H2O → 5CaSO4.2H2O + HF + 3H3PO4
Ammonium sulfate is an important nitrogen fertilizer and is commonly produced as a byproduct of coking programs in iron and steel plants. The reaction of ammonia produced in the thermal decomposition of coal with excess hydrogen sulfate causes the ammonia to crystallize as a salt (often brown due to iron contamination) and sold to the chemical industry.
Another important application of this industrial acid is the production of aluminum sulfate, which is also called “paper making alum”. This compound reacts with small amounts of soap on paper fibers and produces gelatinous aluminum carboxylates; As a result, it leads to coagulation of pulp fibers on the paper surface.
This compound is also used to make aluminum hydroxide; Aluminum hydroxide is used in water treatment plants to purify impurities and also to improve the taste of water. Aluminum sulfate is made by reacting bauxite with sulfuric acid:
2AlO(OH) + 3H2SO4 → Al2(SO4)3 + 4H2O
2- Use as a cleaning agent in the industry: This acid is used in large quantities in the iron and steel industry to remove oxidation, rust and scaling from rolled sheets and profiles before they are sold to the automotive industry.
3- The use of sulfuric acid as a catalyst: Sulfuric acid is used for other purposes in the chemical industry. For example, this acid catalyst is known to convert cyclohexanone oxime to caprolactam, which is used to make nylon.
Another example is sulfuric acid, as a catalyst for the reaction of isobutane with isobutylene to produce isooctane, a compound that increases the octane rating of gasoline (gasoline).
4- The use of hydrogen sulfate as an electrolyte: This substance acts as an electrolyte in lead-acid batteries (lead-acid batteries):
In the Andes:
– Pb + SO42- ⇌ PbSO4 + 2e
At the cathode:
PbO2 + 4H+ + SO42- + 2e– ⇌ PbSO4 + 2H2O
In general:
Pb + PbO2 + 4H+ + 2SO42- ⇌ 2PbSO4 + 2H2O
5- Home consumption of sulfuric acid: This material in high concentrations is often the main ingredient of acid cleaners for draining pipes and sewer lines. This acid is used to remove grease, hair, tissue, etc. stuck in pipes.
SAFETY OF SULFURIC ACID
Sulfuric acid, especially when it has a high concentration, can cause very severe burns; As with other corrosive acids and alkaline compounds, this reaction occurs.
Acid easily decomposes proteins and lipids through amide and ester hydrolysis due to contact with living tissues such as skin and flesh. By strongly absorbing water, sulfuric acid releases excess heat and causes secondary burns.
Accordingly, it can cause permanent blindness if splashed in the eyes. If swallowed, it damages internal organs and is irreversible and may even be fatal.
Therefore, protective equipment should always be used when working with this acid. In addition, its strong oxidizing properties make it highly corrosive to many metals. For these reasons, the damage caused by sulfuric acid is potentially more severe than that of other strong acids such as hydrochloric acid and nitric acid.
This acid should be carefully stored in containers made of non-reactive materials (such as glass). Solutions stronger than 1.5 M of acid should be labeled “CORROSIVE”.
While acid solutions with concentrations greater than 0.5 M and less than 1.5 M should be labeled “IRRITANT”.
First aid for acid spills on the skin, as with other corrosive agents, is to wash with plenty of water. Washing should be continued for at least ten to fifteen minutes to cool the tissue around the acid burn and prevent secondary damage.
H2SO4 is non-flammable. Exposure to aerosols released from sulfuric acid in high concentrations leads to immediate and severe irritation of the eyes, respiratory tract, and mucous membranes. It may even increase the chance of lung cancer by 64%.
THE DANGERS OF DILUTING HYDROGEN SULFATE
Preparation of diluted hydrogen sulfate can be dangerous due to the heat released in the dilution process. To prevent the acid from splashing out of the container, the concentrated acid is usually added to the water, not the other way around.
The heat capacity of water is higher than that of acid, so the cold water container absorbs heat by adding acid.
Also, because acid is denser than water, it sinks to the bottom of the container. Heat is released at the bottom of the container, which is why sudden additions may cause the acid to splash out.
Preparation of solutions with a concentration greater than 6 M (35%) is most dangerous, as the heat produced may be sufficient to boil the dilute acid; For this, it is necessary to use mechanical stirring and an external cooling agent (such as an ice bath).
The reactivity rate of hydrogen sulfate doubles for every 10 degrees Celsius increase in temperature. Therefore, as dilution continues, the reaction will become more intense; Unless the mixture is given enough time to cool. Adding acid to hot water causes a more intense reaction. Keep this in mind about the dangers of sulfuric acid.
STORAGE CONDITIONS OF HYDROGEN SULFATE
In order to keep the concentration of vapors released from hydrogen sulfate low, storage tanks and barrels should be well ventilated. Workers who deal with this acid must follow all safety measures and wear full coveralls.
Goggles, multi-layer rubber gloves, multi-layer mask, thick clothing and long sleeves are always and always important. If possible, it is recommended to wear work boots. Workers must be well trained to work with this acid and how to deal with accidents caused by it.
If stored in non-reactive containers, keep container lids tightly closed. Sulfuric acid storage tanks should not be metal in any way; The acid reacts with the metal and hydrogen is released.
SULFURIC ACID PACKAGING
Merck’s sulfuric acid packages for laboratory use are usually supplied in 2.5 liter glass containers, or 1 liter, 5 liter, 10 liter and 20 liter volumes in polyethylene containers.
The packaging of industrial and edible sulfuric acid for consumption in the industry is generally in polyethylene barrels with a volume of 220 liters. Bulk shipping is also possible. The purchase price of sulfuric acid in each package is different.
TECHNICAL DATA SHEET OF SULFURIC ACID
| NO | Requirements | Specification |
|---|---|---|
| 1 | Vapour pressure | 0.001 mm Hg (20°C) |
| 2 | Viscosity | 26.7 CP (20°C) |
| 3 | Odour | odourless |
| 4 | Melting point | 10°C |
| 5 | Density | 1.84 g/cm³ |
| 6 | Boiline Point | 337°C (610 K) |
| 7 | Solubility in water | miscible |
| 8 | Molar mass | 98.079 g/mole |
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