anchor: Use of 3.6 mg/L (anhydrous) sodium thiosulfate will reduce 1.0 mg chlorine/L (APHA, 1992).
positive: Use of  3.6 mg/L (anhydrous) sodium thiosulfate will reduce levels of 1.0 mg chlorine/L
negative: Use of  3.6 mg/L (anhydrous) sodium thiosulfate has no effect on levels of 1.0 mg chlorine/L.