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Chlorides in Caustic Soda

The EZ-Chloride™ on-line analyzer system is used in chlorine production plants to monitor precisely chloride levels during electrolysis. This approach guarantees quality of the NaOH end product and prevents premature failure of the membrane.


The production of chlorine involves electrolysis of brine that is obtained by dissolving sodium chloride or potassium chloride in water. The anode compartment of electrolysis cells serves for the electrolytic decomposition of aqueous brine, while in the cathode compartment, electrolysis of water takes place. The sodium ions from the anolyte compartment passing through the membrane combined with the hydroxyl ions generated in the catholyte compartment results in the formation of aqueous caustic soda solution. On-line analysis of the caustic soda during electrolysis process guarantees the quality and if needed, corrective action can be taken.

Monitors caustic soda production process to reduce give-away

Controls chloride concentration in caustic soda during the chlorine / caustic production process

Guarantees caustic soda purity by proper membrane operation

Avoids off-spec quality of caustic soda by 100% control

Detects premature failure of membranes

Typical measuring ranges  
0 – 100 ppm Cl-

Analysis methods  
Turbidimetric measurement after addition of AgNO3

Detection limit 

Cycle time    
6 – 10 minutes (T90)

Better than ± 2 % full scale range
(standard test solutions)

Parameters: Chloride

Product type: Process analyzers

Measuring technology: ISE potentiometry

Type of application process: Chlorine electrolysis

Industries: Chlor-alkali