Sulfuric acid plays an essential role in various industries, particularly as a precursor and a reagent in a wide range of chemical reactions. Mass-producing different types of industrial products like plastics would not be possible without sulfuric acid, but its importance in everyday life is often taken for granted or overlooked by most people.
Aside from industrial uses, sulfuric acid also has several common everyday uses, including household cleaning products and battery electrolytes. It is used in various concentrations, but its corrosiveness and toxicity make it very dangerous, especially when ingested. Extra precautions should be taken when handling and storing sulfuric acid.
What is sulfuric acid used for?
The different uses of sulfuric acid can be grouped into three main categories, namely, for industrial use, household use, and use in batteries.
The industrial applications of sulfuric acid are the widest ranging and the most important, simply because of their economic impact. Household applications are narrower in scope, are mainly for cleaning purposes. Finally, the battery use is the most common, because it’s used in car batteries, and it’s also the most specific daily use of the acid.
Industrial applications of sulfuric acid
Sulfuric acid is widely used in the industrial production of synthetic fertilisers like ammonium phosphate.
This chemical is an organic salt that is rich in nitrogen and sulphur, making it ideal as a soil fertiliser. It is also useful as a fire retardant because it increases the combustion temperature threshold of materials. It is produced by the reaction of ammonia and sulfuric acid:
2NH3 + H2SO4 🡺 (NH4)2SO4
Other types of synthetic fertilisers produced by using sulfuric acid as a reactant include superphosphate of lime and calcium dihydrogenphosphate.
In fact, the largest industrial use of sulfuric acid is the manufacture of phosphate fertilisers, which accounts for 50% of its industrial applications.
- Other chemicals
Sulfuric acid is also used in the mass production of other industrial chemicals like hydrochloric acid, nitric acid, pigments and dyes, explosives, and pharmaceutical products. The acid is also crucial in manufacturing rayon.
- Refining crude oil
Refining fossil fuel into gasoline, diesel, kerosene, and other petroleum products would be very difficult without sulfuric acid. It’s used to remove impurities from crude oil. Without sulfuric acid, plastics are almost impossible to mass-produce.
- Processing metals
Sulfuric acid is very useful in processing metals, such as during cleaning and electroplating processes. For instance, it’s used to clean iron and steel before electroplating them with tin or zinc. This step is crucial in preventing rust or the oxidation of iron or steel. The layer of tin or zinc serves as extra protection against oxidation.
- Paper production
The cellulose from trees and recycled paper is processed using sulfuric acid. The cellulose is converted into pulp, which then can be processed into paper by adding a binding agent. About 1% of the total applications of sulfuric acid is for paper production.
Household applications of sulfuric acid
When it comes to household applications, sulfuric acid is mainly used as the active ingredient in many cleaning products. From industrial-strength drain cleaners to detergents, sulfuric acid is very effective because of its corrosive property. It can effectively dissolve both organic and inorganic materials.
In lower concentrations, sulfuric acid is used as an ingredient in powdered laundry detergents, hand soap, dishwashing liquid, and as components of pet shampoos. However, not all products of these types have sulfuric acid content.
Arguably, the most common and widespread use of sulfuric acid in daily life is as battery electrolytes. The global use of batteries in cars and in renewable energy sources like solar and wind power systems makes sulfuric acid indispensable at the moment. Although there are alternatives like lithium batteries, lead batteries are still the most common because they are cheaper to manufacture.
What can you do with sulfuric acid?
As previously mentioned, sulfuric acid has a wide range of industrial applications. It is essential in manufacturing pharmaceutical and cosmetic products, and serves as a precursor and reagent in many industrial chemical reactions. The global demand for sulfuric acid is so high that the world produces an estimated 231 million tonnes of it annually.
If you’re working as a chemist or a chemical engineer, there are many things you can do with sulfuric acid. However, if you’re an ordinary individual without scientific training, the most that you can do with the acid is to use it as cleaning liquid for the bathroom and drain. (You inevitably use it when you are starting your car because of the electrolytes in the car battery.)
You should be very cautious in handling this type of acid because it is very corrosive and toxic when ingested. Immediately wash any affected skin surface that comes contact with the acid. Use protective goggles, gloves, and aprons when handling during a laboratory experiment. You should also use a mask to minimise the risk of inhaling its fumes.
Although sulfuric acid is used in manufacturing fertilisers, this is not its direct use in agriculture. The direct agricultural use of the acid is very limited. For example, it is used by specialist contractors in the process of harvesting potatoes. A solution of the acid is sprayed on fields of potatoes before harvesting to dry the stems and prevent them from becoming tangled with the harvesting equipment.
Does sulfuric acid evaporate?
Various factors affect the evaporation rate of a liquid. These include the volatility of the substance, temperature, concentration in a solution, and pressure. Under normal conditions, sulfuric acid has a very low vapour pressure. This means that it does not easily evaporate, unlike other substances with high vapour pressure like alcohol and gasoline.
Other examples of acids that have low vapour pressure are phosphoric acid and perchloric acid. The evaporation rate of sulfuric acid is less than 1, using butyl acetate as a benchmark with rate of 1. Significant evaporation of sulfuric acid occurs only in temperatures above 150 °C.
What temperature does sulfuric acid freeze at?
Just like the evaporation rate, the freezing point of sulfuric acid varies depending on several factors like concentration and pressure. At normal pressure at 30% concentration, the freezing point of sulfuric acid is 10°C, which is higher than the freezing point of pure water.
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