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Sodium Compounds in Sodium Hypochlorite

The EZ-Bleach® on-line analyzer system harnesses proprietary AppliTek technology to simultaneously measure the three critical process parameters in bleach production:  sodium hydroxide (NaOH), sodium carbonate (Na2CO3) and sodium hypochlorite (NaOCl). Monitoring these parameters allows you to control the caustic setpoint despite possible changes in the values of these and keep control of overall process behaviour.

The analyzer system is supplied as a standalone fiberglass reinforced cabinet, combining the actual process analyzer with a proprietary sample preconditioning system.


The production of bleach is an established process by the reaction of chlorine and sodium hydroxide solution formed as major co-products from chlor-alkali operations. The instable and pH critical nature of the bleach production process may cause the generated sodium hypochlorite to decompose through multiple pathways with several consequences. Accumulation of oxygen gas can lead to a dangerous increase in pressure as well as high mechanical wear in pumps. Chlorate formation is probably the largest commercial loss in bleach production and requires a safe and ideal range of excess caustic. The minimum amount of excess caustic is depending on temperature and sodium hypochlorite concentration and needs careful monitoring to control the setpoint.


Typical measuring ranges    
NaOH: 0 – 10 g/kg / Na2CO3: 0.5 – 10 g/kg
NaOCl: 20 – 200 g/kg

Analysis methods  
Acid-base titration using HCl
Iodometric titration using sodium thiosulphate

Detection limit

Cycle time    
10 minutes

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

Product type: Process analyzers

Measuring technology: Titration

Type of application process: Bleach production, Chlorine drying compression

Industries: Chlor-alkali