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Chemistry | NaOH | Online concentration measurement of binary NaOH solutions

NaOH is a major building block in various chemical processes. In the manufacture of other chemicals, soaps, detergents, textiles, paints, glass and ceramics or for water treatment and CIP processes it is used in different concentrations. An accurate control of the required NaOH concentration is important and can easily be accomplished with Anton Paar's density sensor L-Dens 7400 Version INC or sound velocity sensor L-Sonic 5100 Version MON.

Concentration measurement of aqueous NaOH solutions

Sodium hydroxide (NaOH), also known as caustic soda, is a strong base, which is highly soluble in water. It forms an alkaline solution when dissolved in water and is one of the strongest bases commonly used in industry.

For aqueous NaOH solutions, there is a very good correlation between concentration and density or sound velocity values, making both density and sound velocity measurement ideal for accurate concentration measurements.

Application Examples

NaOH is a base chemical in various chemical processes and also widely used for CIP processes in food and beverage industry.

Production of NaOH

The electrolysis of NaCl is the most important way to produce caustic soda, whereby the Membrane Cell Process is state of the art.

The NaOH leaves the electrolysis cell with 25–32% and must be monitored with density (D) or sound velocity (S) measurements to maintain safe concentrations and not to damage the membranes. In an evaporation step the NaOH solution is further concentrated to approx. 50%, which is controlled with a density sensor.

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