A Short Guide to Making Sodium Hydroxide

Sodium hydroxide (NaOH), otherwise called lye or caustic soda, is a burning metallic base. A soluble base, burning soft drink is broadly utilised in numerous businesses, for the most part as a solid compound base in the production of mash and paper, materials, drinking water, and cleansers by electrolysis. Overall creation in 1998 was around 45 million tons. Sodium hydroxide is additionally the most well-known base utilised in substance research centres, having the option to test for a lot of cations (this is called Qualitative Inorganic Analysis) and give basic mediums to certain responses that need it, for example, the Biuret test. 

How to Prepare:

The strong base sodium hydroxide is a common and useful one. Preparing a formula of sodium hydroxide (NaOH) in water requires extra caution because the exothermic reaction releases a lot of heat. The solution may spatter or boil. Here’s how to manufacture a sodium hydroxide solution safely and recipes for a variety of NaOH strengths by electrolysis.

Kellener – Castner Process

The Castner-Kellner approach makes the formula of sodium hydroxide and is based on the following principle. The electrolysis of an aqueous NaCl solution produces NaOH.

The Castner-Kellner cell is a type of cell that was invented by Castner and Kell. It’s a steel rectangular tank. Ebonite is used to line the inside of the tank. Titanium is used as an anode. The cathode is a flowing layer of mercury (Hg) at the bottom of the tank.

2NaCl →  2Na+ + 2Cl–  ionisation of NaCl 

Positive and Negative ions migrate towards their respective electrodes when an electric current is passed through the brine. At the mercury cathode, Na+ ions are released. Sodium Amalgam is formed when sodium is placed on mercury. The anode-produced chlorine is removed from the cell’s top. Because of the large overvoltage, Na+ ions are discharged before H+ ions.

The Production of NaOH:

Amalgam is transported to a separate chamber known as the ‘denuder,’ where it is processed with water to generate NaOH in a liquid state. The evaporation of this solution yields solid NaOH.

2Na/Hg + 2H2O → 2NaOH + H2 

The NaOH produced is extremely pure, and the process is extremely efficient.

Loewig’s Process

The preparation of caustic soda by Loewig is based on the creation of sodium ferrate, which is then destroyed by water. The soda liquors are combined with ferric oxide, then dried and calcined at a bright red temperature, commonly in a revolving furnace. Calcination causes a reaction between sodium carbonate and iron oxide, resulting in carbon dioxide being released and sodium ferrate staying in the furnace. The sodium ferrate is decomposed, caustic soda is formed, and iron oxide is regenerated after being washed with cold water until all soluble matter is removed; then water at 900 C is run over the sodium ferrate, which causes it to decompose, caustic soda to form, and iron oxide to regenerate; the last is returned to the calcining process.

The Procedure Followed by LeSueur

Lunge’s device is used in this method. The slanting cathode is made of iron wire gauze. The diaphragm rests on it, which is made up of two parts: a parchment paper sheet and a double sheet of asbestos cemented together with blood albumin that has been solidified and hardened with potassium bichromate treatment. 

The anode, constructed of lead and contained carbon rods dipped into the salt solution, was housed in an earthenware bell. Outside the bell, caustic soda is generated, and the hydrogen was predicted to escape rapidly due to the cathode’s sloped location, preventing polarisation. However, the acidic soda solution dissolved the earthenware bells in practice, releasing hydrogen.

Mercury Cell Process

At a mercury cell’s cathode, sodium metal produces an amalgam, which reacts with water to make NaOH. Mercury leaks have been a source of concern, while newer plants claim to be safe in this aspect. Diaphragm cell procedure — employs a steel cathode and a porous diaphragm to prevent NaOH from reacting with Cl2. A permeable diaphragm separates the anode and cathode areas in the diaphragm cell process. The brine is introduced into the anode compartment and flows into the cathode compartment via the diaphragm.

The cell is filled with diluted caustic brine. Typically, the caustic soda must be concentrated at 50% and the salt removed. This is accomplished using an evaporative process that uses approximately three tonnes of steam for every tonne of caustic soda. To saturate diluted brine, remove the salt from the caustic brine. Because chlorine contains oxygen, liquefaction and evaporation are frequently used to purify it. Membrane cell process — a Nafion membrane separates the cathode and anode processes, similar to the diaphragm cell method.

 The membrane allows just sodium ions and a small amount of water to pass. It generates NaOH of greater purity. The mercury cells process uses the least amount of electricity and requires the least quantity of steam for caustic concentration (less than one tonne per tonne of caustic soda).

Extraction of NaOH

In a stainless steel, platinum, or titanium evaporating dish, boil the solution you just created. This stage should always be performed in a professional laboratory at a college, institution, or business. Place the dish on a boiler and pour the solution into it gently. Because water boils at 100 degrees Celsius and NaOH at 1,390 degrees Celsius, boiling will separate the two. Boil it in a fume hood if at all possible.

• If you boil your solution with mercury cells, it will melt your dish.
• In a non-chemically built ventilated room, boil your solution.
• While handling the solution, wear chemical gloves. When NaOH comes into touch with your skin, it produces severe chemical burns.

Conclusion

Because of the chemical’s fire hazard and electrolysis process, care should be taken when handling sodium hydroxide for use, especially in bulk amounts. Small-scale laboratory use of sodium hydroxide can be stored in bottles. It should be kept in intermediate bulk containers to handle and transport cargo (medium volume containers). NaOH ought to be held in huge fixed stockpiling tanks with up to 100,000 gallons for broad use, for example, in assembling or wastewater plants.

Carbon steel, polyvinyl chloride (PVC), treated steel, and fibreglass-built up plastic are the most ordinarily involved materials in NaOH stockpiling holders (FRP, with a safe liner). Hermetically sealed compartments are expected for sodium hydroxide capacity and mercury cell.