The method is divided into three operations, the nrst being the evolution of hydrogen sulfide, the second being its fixing to a silver nitrate test paper, and the third is measurement of sulfur in the test paper by X-ray fluorescence spectrometry. Hydrogen sulfide was made by heating the sample with tin(II)-strong phosphoric acid reagent (500 g of reagent grade phosphoric acid was concentrated and heated to 270°C. To this 40 g stanous chloride dihydrate was added and the mixture was heated again to 290°C). The method was applied to the determination of sulfur in iron and steels. Procedure Place a sample containing up to 25μg of sulfur into the reaction tube. Add 10 ml of tin(II)strung phosphoric acid reagent and connect the capture part to which a test paper has been attached. Heat the contents for. 15 minutes in a stream of nitrogen (45 ml/min) on a furnace whose temperature has been regulated at 400°C. Transfer the test paper to a sample holder and measure the intensity of SK_α line. The intensity was proportional to the sulfur amount (1 to 25 μg). The coefficient of variation was 3.5% (with 10 μg of sulfur) in five runs.