The Test Methods for Reactive Sulfide

Total and Dissolved Sulfide

• This method approved by the National Pollutant Discharge Elimination System (NPDS) through the Environmental Protection Agency (EPA) uses a spectrophotometer and is applicable to measuring total and dissolved sulfides in drinking, surface, and waste water. In this method, sulfide reacts with dimethyl-p-phenylenediamine in the presence of ferric chloride to produce the dye, methylene blue. The dye is then measured using a spectrophotometer at a 625-nanometer wavelength. The results indicate the concentration of reactive sulfide in the sample.

Distillation Method for Acid Soluble Reactive Sulfide Compounds

• The distillation method is used to determine the amount of sulfides in aqueous, solid waste and effluent (waste water) samples. This method determines sulfide in compounds that are acid-soluble. The sulfide is separated from the sample matrix by the addition of sulfuric acid.

  The sample is then heated to 70 degrees Celsius. Hydrogen sulfide is formed and distilled. The hydrogen sulfide is then streamed by nitrogen into a zinc acetate gas bottle. Zinc sulfide precipitate forms. The sulfur is oxidized by adding iodine with two milliliters of 6N hydrochloric acid. The iodine is titrated with a standard solution of phenyl arsine oxide until blue iodine starch disappears. The concentration of sulfide in the zinc sulfide precipitate is then quantified an ion selective electrode.

Distillation Method for Acid InSoluble Reactive Sulfide Compounds

• The distillation method for acid-insoluble reactive sulfide compounds is the same as in acid- soluble compounds, in which the sulfide is separated using sulfuric acid, heated to 70 degrees Celsius and carried into zinc acetate gas bottles to enable zinc sulfide precipitate to form. However, the sulfur is oxidized by adding 10 milliliters of 6N hydrochloric acid. The iodine is then titrated with a standard solution of phenyl arsine oxide until blue iodine starch disappears and quantified using an ion selective electrode.

Gas Detector Tube Method

• The Gas Detector Tube method is used by waste treatment, storage, disposal, and remedial companies to determine the presence of potentially hazardous reactive sulfides in liquids, sludges, and solids. This method measures gases that enter air spaces at heights of 10 feet from mixing pit of 10 units square. The gas is sampled into the detection tube containing detection agents. The concentration of the sulfide in the gas is read automatically due to the change in the color of the detecting agent.

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