A

Source: Horiba Instruments.

Notes: O: Recommend, A: Applicable, X: Not applicable.

Source: Horiba Instruments.

Notes: O: Recommend, A: Applicable, X: Not applicable.

WITH ULTRASONIC CLEANER WITH WATER-JET CLEANER WITH BRUSHING CLEANER

WITH ULTRASONIC CLEANER WITH WATER-JET CLEANER WITH BRUSHING CLEANER

FIG. 7.7.7 Submersion assemblies with various cleaners. (Courtesy of Horiba Instruments)

FIG. 7.7.7 Submersion assemblies with various cleaners. (Courtesy of Horiba Instruments)

glass. In addition, cleaning cycles that are too frequent or too long can cause premature failure of the glass electrode. As with the water jet, the cycle timer must hold the last pH reading and suspend control action during the wash cycle. Redundant pH sensors can be installed in parallel so that while one electrode assembly is being reconditioned, the other is in control. In such installations, the reconditioned assembly automatically returns to control after the wash cycle.

Wastewater treatment facilities often manually clean electrodes by soaking them in a dilute hydrochloric acid solution for several hours. Soaking electrodes for 1 min in a dilute solution of hydrofluoric acid in a nonglass container can reactivate electrodes that are sluggish or have too small a span or efficiency. The reactivation occurs by the hydrofluoric acid dissolving part of the aged gel layer. The electrode should then be soaked overnight in its normal storage solution (typically a 4-pH buffer).

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