Description

An acidified sample containing a starch indicator is titrated with a standard potassium iodide-iodate titrant to a faint permanent blue end point which appears when the reducing power of the sample has been completely exhausted.

This method is applicable to drinking and surface waters, sewage and industrial wastes. The primary application has been to cooling,process and distribution water systems and boiler feedwaters to which sulfide is added in order to reduce dissolved oxygen and eliminate corrosion.

The minimum detectable limit is 2-3 mg/L SO3