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AJAX Google Translator


Original site in Italian language, the translations are handled automatically by the program using Google translation

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Caustic Soda

Manufacturing Process

Over 95% of production capacity of chlorine, and essentially 100% of the production capacity of caustic soda in its hydrated form, sodium hydroxide (NaOH) are based on the electrolysis of brine.

In this process the sodium chloride (NaCl, salt) in solution (brine) is electrolytically decomposed to elemental chlorine (anode compartment), and the solution of sodium hydroxide and hydrogen elements (cathode compartment).


The overall reaction for the electrolytic production of caustic soda and chlorine is:

NaCl +2 H 2 O 2







Electrical Power


H 2 +2 NaOH


The electrolytic process for the production of caustic soda, using as raw material, sodium chloride, is a co-production, for each 1.1 kg of sodium hydroxide product is also produced 1 kg of chlorine. This ratio is defined as an electrochemical unit (ECU).

stability and shelf life

caustic soda solution is a stable product, but its shelf life depends on storage conditions. If caustic soda is exposed to air, a change in the quality of the product occurs over time, as the caustic soda solution absorbs carbon dioxide and form sodium carbonate (Na 2 CO 3) also increases the percentage of iron absorbed from the common storage vessels in carbon steel. Therefore, minimizing its exposure to air and its direct contact with metals that contain iron improves the shelf life of the caustic soda solution.


EC Directive
If noted on the specification, on the basis of analysis (as NaOH) of 48.5 to 51.5%, Dow caustic soda solution meets the requirements of the following test Official Journal of the European Communities - Directive 2008/84/EC of the Commission.
carbonate (as Na 2 CO 3) - 0.25% maximum
Arsenic (as As) - 1.5 mg / kg max
Lead (as Pb) - 0.25 mg / kg max
Mercury (as Hg) - 0.5 mg / kg max

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