Concentration Measurement of Sodium Hydroxide Solutions by Refractive Index

The concentration of sodium hydroxide in water can be easily and quickly determined by refractive index measurement.

Sodium hydroxide - the most common base in the world

Sodium hydroxide (NaOH, caustic soda, lye) is a strong alkali (base). It is used as flakes, granules or as an aqueous solution, mostly at concentrations of 48 % to 50 %. NaOH is used in many industries:


  • Pulp and paper: bleaching processes and to separate lignin from cellulose fibers
  • Chemical processing: for downstream products, e.g. solvents, plastics, fabrics, adhesives, coat-ings, herbicides, dyes, inks, pharmaceuticals
  • Textiles: in polyviscose fiber production, cotton and dye processing, synthetic fibers
  • Soap and detergents: in saponification (converting fat, tallow and vegetable oils into soap) and to manufacture anionic surfactants
  • Petroleum exploration and processing: as an additive in drilling mud, to increase alkalinity in bentonite mud systems, to neutralize acid gas
  • Food and beverage: water treatment, food processing, cleaners for beverage bottles

The Abbemat Refractometer family from Anton Paar

Conventional concentration determination of sodium hydroxide solution is done by titration, which is a slow, time-consuming process. Moreover, NaOH and CO2 form hydrocarbonate and carbonate during the titration process, which changes the pH and, depending on the time of titration, may lead to wrong measurement results. 

With the help of a customized function, an Abbemat Refractometer from Anton Paar directly shows the concentration within seconds by using a flow-through cell and a sample changer with the Abbemat Performance Plus Line. As only small amounts of sample are required, the costs of disposal of waste are lower and the process is more environmentally-friendly than conventional titration. All Abbemat

Refractometers have internal Peltier elements which allow the determination of the refractive index and concentration with high accuracy.

Learn more about the Abbemat Refractometers

Drugi relevantni instrumenti

Apart from the Abbemat Refractometer, a Density Meter from Anton Paar can be used for concentration determination.

Dobro je znati

The Abbemat Refractometers from Anton Paar are ideal for determining the concentration of sodium hydroxide solutions.