1. Purpose and Scope

1.1 This test method determines the total alkali content of a bleach bath containing hydrogen peroxide and alkali from any source. The total alkali content is expressed as % sodium hydroxide. 1.2 Alkali in bleach baths may be supplied by sodium hydroxide, sodium silicate, sodium carbonate, or by various other alkaline materials, including potassium compounds, ammonia, lime, or by peroxygen solids which contain alkaline salts. 1.3 The alkali content of a bleach bath is a critical parameter in determining the rate and extent to which the textile being bleached is affected by the bleaching process. 1.4 This test method is used for laboratory determinations and for process control.

2. Principle

2.1 A weighed specimen of the bleach bath is titrated with a standardized solution of sulfuric acid to a Phenol Red endpoint, or to the pH range 6.8-8.4 on a pH meter. The total alkali, expressed as % NaOH, is calculated based on the weight of the bath.