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Suppose you’ve been experimenting with a few of the simple chemical reactions in our “Chemistry Reactions” experiment. In that case, you may have also noticed that some of these experiments had a white precipitate forming. This is often due to either calcium hydroxide or sodium chloride (NaCl). Calcium hydroxide and sodium chloride are two components of the Leblanc process. In soda production, they are often used to remove phosphoric acid, carbon dioxide, and various metals from raw materials such as iron pyrites that can contaminate the final product. The Leblanc process was invented by French chemist Nicolas Leblanc in 1791.
Leblanc Process History
The Leblanc Process (also called the Leblanc Alkali Company) was a large chemical process plant in Toulouse, France, which manufactured soda ash (primarily sodium carbonate, Na2CO3) using the Solvay process from 1821 until 1985. The plant was founded by Claude Evariste Nicolet, who named it after a former colleague who had been the manager of the company’s most successful predecessor.
About the Leblanc Process
The first major step involves the transformation of iron pyrites into ferrous sulphate. This is done by mixing hot iron pyrites with calcium hydroxide and water solution. This creates an important chemical reaction that generates carbon dioxide. The reaction is exothermic, meaning that the temperature of the reaction rises and results in a net release of heat. Therefore, adding sodium chloride (NaCl) is necessary to balance out the excess heat and keep it from rising above a certain temperature.
The calcium hydroxide reacts with carbon dioxide to produce calcium carbonate and water. Sodium chloride (NaCl) acts as a catalyst for the reaction between calcium hydroxide and carbon dioxide. This causes the rapid formation of sodium sulphate, which is subsequently separated from the water. The hot water is isolated, and the remaining reaction liquid is cooled. This causes the salt to crystallise out of the solution, leaving behind a brine with high concentrations of calcium carbonate.
This liquid contains nearly 80% calcium carbonates, 18% sodium chloride, and just a few other trace elements. It is then fed into a second stage where it comes in contact with bone-ash (a form of sodium carbonate) and ammonia to produce sodium bicarbonate and calcium ammonium nitrate. The calcium ammonium nitrate is then treated with sulfuric acid to convert it into calcium sulphate and ammonia, then distilled away.
The ammonium sulphate is further treated with water to remove impurities, leaving behind a mixture of component salts. These component salts are sold for use in industrial processes and as fertilisers (ammonium sulphate makes a great fertiliser). The remaining solution from the distillation process contains phosphoric acid, but it also contains iron, lead, and other metals. Depending on the desired end product, these metals may be removed using the Leblanc process again with calcium hydroxide and sodium chloride (NaCl).
How Does the Process Work? (The Calcium Brine)
Most people know that calcium carbonate is a white solid that is commonly found as beach sand. Many people also know that it can be found in nature as coral skeletons. We all absorb calcium from food and drink, but our bones absorb less than 10% of it throughout our lifetime.
The Leblanc process produces a large amount of calcium carbonate without the use of bone. Instead, it involves reacting the molten iron pyrites with a strong solution of calcium hydroxide (Ca(OH)2) and water. This creates a highly alkaline solution that is rich in calcium and carbonate. As the reaction continues, calcium carbonate precipitates out of the solution:
Calcium hydroxide + carbon dioxide ⇒ calcium carbonate + water
Advantages and Disadvantages of the Leblanc Process
- Advantages:
Produces a large amount of calcium carbonate quickly and inexpensively
Low-temperature reaction process doesn’t require expensive equipment or lots of heat (water is often the coolest thing!)
Doesn’t require a lot of water because precipitation occurs at low temperatures. This allows for waste heat to be used in other processes that do require lots of heat.
- Disadvantages:
Calcium hydroxide solution is highly corrosive, making it a bad choice for transporting through pipes.
Sodium chloride (NaCl) is added to ensure temperatures don’t rise above a certain level. This results in the formation of sodium sulphate, which is difficult to recover from the product. It is also expensive and must be mined from underground salt deposits.
This process doesn’t result in the complete removal of phosphoric acid, so it must be treated with additional chemicals for any further use. This adds to the cost of production time and money.
Conclusion
The Leblanc process is not the most efficient way to produce calcium carbonate, but it is inexpensive and doesn’t require complicated equipment. This makes it perfect for those who want a quick and easy method of producing high-grade calcium carbonate in a small amount of time. So the Leblanc process has many advantages over other extracting or manufacturing CaCO3. This process is not only cheap but is also an environmentally friendly process. When you follow all the steps, we can manufacture calcium carbonate easily at home without any other commercial
