Methods to Prepare NaOH

Caustic Soda aka NaOH or Sodium Hydroxide can be prepared by various methods which are given below:

• Nelson-Diaphragm Cell Method
• Loewig’s Process
• Castner-Kellner Process

These are a couple of industrial methods by which NaOH can be prepared. Let’s discuss Nelson-Diaphragm method among them:

Nelson-Diaphragm Cell Method

This is an industrial methods and essential for large-scale industries to produce caustic soda. This method offers a way to produce NaOH while we keep sodium hydroxide and chlorine separately in this method.

The chemical reaction of Nelson-Diaphragm Cell method is:

2NaCl (salt) + 2H₂O (water) + electricity → Cl₂ (chlorine) + H₂ (Hydrogen) + 2NaOH (Sodium Hydroxide)

Let’s understand this process in following steps:

Step 1: An electrolytic cell consists a container which has 2 compartments: 1) Anode Compartment, 2) Cathode Compartment. These 2 compartments are separated by a diaphragm. This diaphragm is made by asbestos. At anode compartment, Cl ions are present and in cathode compartment, OH ions are present.

Step 2: Now, you should have a brine solution which is typically formed by dissolving NaCl (Sodium Chloride) in H₂O (water). This brine solution acts as an electrolyte and important for an efficient process.

Step 3: Using electrodes, an electric current is being passed through this brine solution.

Step 4: At anode compartment (Positive electrode), Cl ions are oxidized to form chlorine gas (Cl2):

2Cl^– → Cl^– + 2e^–

Step 5: At cathode compartment (negative electrode), water is reduced to form hydroxide ions and hyrogen ions:

2H₂O + 2e^– → H₂ + 2OH^–

Step 6: These hydroxide ion (OH^–) travels through the diaphragm to the anode compartment and reacts with sodium ions (Na⁺) to form sodium hydroxide:

Na⁺ + OH^– → NaOH

Step 7: Now, chlorine gas is collected at the anode., hydrogen gas is collected at the cathode and sodium hydroxide is also collected from cathode compartment. Chlorine and sodium hydroxide can’t be mixed due to diaphragm.

Step 8: The collected products undergo a purification process to ensure the quality and purity of chlorine, hydrogen and sodium hydroxide.

Step 9: The overall reaction is as follows:

2NaCl (salt) + 2H₂O (water) + electricity → Cl₂ (chlorine) + H₂ (Hydrogen) + 2NaOH (Sodium Hydroxide)

Loewig’s Process

Loewig’s Process includes the electrolysis of sodium chloride (NaCl) solution. In this process, a brine solution (NaCl dissolved in water) serves as the electrolyte. The chemical reactions occurring at each electrode are:

At the time of electrolysis, chlorine gas is produced at the anode:

2Cl^– → Cl₂ + 2e^–

At the cathode, hydrogen gas and sodium hydroxide are formed:

2H₂O + 2e^– → 2OH^– + H₂

Now, the complete reaction will be:

2NaCl + 2H₂O → Cl₂ + H₂ + 2NaOH

Read More about Elctrochemical Cell.

Castner-Kellner Process

The Castner-Kellner Process also includes electrolysis process but has different setup. In this method, mercury cathode cells are used.

At the cathode, Sodium amalgam is formed:

2Na⁺ 2e^– → 2Na

It reacts with water to form sodium hydroxide and hydrogen gas:

2Na + 2H₂O → 2NaOH + H₂

Here, the chemical reaction has produced NaOH.

Caustic Soda is a solid chemical compound that contains sodium (Na), oxygen(O), and hydrogen(H) ions. The chemical name of Caustic Soda is Sodium Hydroxide. The chemical formula of caustic soda is NaOH. Caustic Soda is basically a base as it releases OH^– ions when dissolved in water.

Caustic Soda is an important compound in chemistry as well as in daily life. In this article, we will learn What is Caustic Soda, what is its chemical formula, and its chemical name. We will also learn about the physical and chemical properties of Caustic Soda and the preparation of Caustic Soda along with its properties and uses.