Most homeowners do not think twice before using bleach on clothing and other articles without realising its harmful effects. Bleach gives off toxic fumes, which are extremely dangerous. While it effectively removes even the toughest of stains, it damages fabrics in the long run, often permanently, and its effects continue long after the fabric has been washed and rinsed. Bleach needs to be neutralised after it has accomplished its intended purpose. Bleach neutralisers refer to chemicals that neutralise the harmful effects of sodium hypochlorite, commonly known as bleach.
Sodium metabisulfite (chemical formula Na2S2O5) is also called disodium disulfite, pyrosulfurous acid and disodium salt. It is often used in the dechlorination of swimming pools, or to lower its chlorine levels. Water treatment plants employ the substance to remove trace of excessive chlorine. Sodium metabisulfite is an effective bleach neutraliser. 2.2 grams (one teaspoon) of sodium metabisulfite added to 2.5 gallons of water effectively neutralises all harmful bleach residue.
Sodium sulphite (chemical formula Na2SO3) is an effective, fast and cheap bleach neutraliser that is easily available at most swimming pool chemical vendors. It is typically used to stabilise high levels of chlorine in a swimming pool, and is sold under the trade names De-Chlor and Knock Down.
Ascorbic acid (chemical formula C6H8O6) is used commercially to neutralise bleach in water storage tanks. Bleach, which is added to water tanks as a disinfectant, needs to be completely eliminated before the water is fit for drinking or agricultural purposes. Ascorbic acid neutralises all residual bleach in a matter of seconds, and 1/4 tsp of the substance added to 1 gallon of water effectively removes all traces of bleach.
Sodium thiosulfate (Na2S2O3) is used in spas to lower bromine and chlorine levels. It is a valuable bleach neutraliser, and is just as effective as sodium metabisulfite, even though it is slightly more expensive.
Acids besides those mentioned in this article should not be used in an effort to neutralise bleach. Vinegar is one such substance that is erroneously purported to have a neutralising effect on bleach. Instead, vinegar acts on the hypochlorite content of bleach, turning it into hypochlorous acid and other dangerous chemicals. Hypochlorous acid can convert to deadly chlorine gas in a low pH solution.
According to Rayna Gillman in the book "Create Your Own Hand Printed Cloth," hydrogen peroxide is an ineffective bleach neutraliser---contrary to popular opinion.