This method is for determining hydrogen sulfide in gas mixtures. Mercaptan sulfur and carbonyl sulfide, if present, are determined as hydrogen sulfide. The accuracy of this method is not sufficient to obtain reliable results below 5 grains of H2S per 100 cu ft (115 mg/m3). This method is intended primarily as a field test. UOP Method 212, "Hydrogen Sulfide, Mercaptan Sulfur and Carbonyl Sulfide in Hydrocarbon Gases by Potentiometric Titration" is recommended for more accurate laboratory determinations.