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Potassium Hydroxide and Sodium Hypochlorite

I am a product development chemist. Currently I am preparing a cleaning chemical solution which contains sodium hypochlorite and potassium hydroxide crystals as major components. The solution is clear, yellowish and stable at 1.75% NaOCl and 14% KOH. When the components are increased (2.1% NaOCl and 25% KOH), I initially get the clear, yellowish solution but after a day it turns to pink and forms suspended black particulates. Why does this happen? I was told that it could occur due to metal impurities but I made sure that I used all equipment made of glass, and still the solution was unstable.

Kae Marquez
- Philippines
2001

This could be due to co-precipitation of hardness salts (calcium and magnesium) with iron. These components will exist at low levels (ppm) within the raw materials used.

Steve Holland
- United Kingdom
2002

Try using a more concentrated form of the solution. I had the same problem, my original components were far to impure and proved thus very unstable.

Rachel Corbin
- Houston, Texas
November 20, 2009

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