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3.2.4 Maximum Potential Acidity by Total Sulfur Determination <br /> 3.2.4.1 PrinciRles-- <br /> This method measures the total sulfur in a sample. If all of the total <br /> sulfur occurs in pyritic forms, the calculation of maximum potential acidity <br /> from sulfur corresponds with actual potential acidity from sulfur. But if <br /> part of the sulfur occurs in other forms, the maximum as calculated will be <br /> too high. This is the reason that such calculations are referred to as <br /> maximums and in doubtful cases approximate determinations should be made <br /> which rule out other sulfur forms (see 3.2.6). These determinations are <br /> not necessary when the maximum acid from total sulfur is within safe limits. <br /> A sample is heated to approximately 1600°C. A stream of oxygen is passed <br /> through the sample during the heating period. Sulfur dioxide is released <br /> from the sample and collected in a dilute hydrochloric acid solution <br /> containing potassium iodide, starch, and a small amount of potassium iodate. <br /> This solution is automatically titrated with a standard potassium iodate <br /> solution. <br /> A trace amount of potassium iodaee reacts with potassium iodide and dilute <br /> hydrochloric acid to yield free iodine, potassium chloride and water. The <br /> free iodine combines with the sulfur dioxide and water to yield sulfuric <br /> acid and hydroiodic acid. The amount of potassium iodate solution used <br /> during the titration is recorded. The calculation of the percent total <br /> sulfur is based on the potassium iodate measurement (Smith et al. , 1974). <br /> 3.2.4.2 Comments— <br /> Some samples, e.g. coal, when first placed in the furnace may change the <br /> color of the solution in the titration vessel to pink or purple (probably due <br /> to organic compounds). Some samples may contain halogens (iodine, chlorine, <br /> fluorine) which darken the solution in the--t it rati onvessel-and_will_there--- - - _ <br /> �—fore produce results that are low. The halogen problem, if encountered, may <br /> be eliminated by the use_of_an_antimony trap-between the-furnace-and _ - <br /> l' T titration assembly. Interference may result with samples high in nitrogen; <br /> -_-however,-_this-does-not-appear-to happen-with-rock-samples. - Additional----- <br /> information <br /> dditional - -information can be obtained by reading Leco Equipment Application 120 and <br /> Instructions for Analysis of Sulfur in Hydrocarbons by the Leco High <br /> Frequency Combustion Titration Procedure. - - <br /> Materials with a low chrome (2 or less) may have a high (over 1.0%) sulfur <br /> '- content; therefore, use a 0.250 g sample when the chrome of the material is <br /> 1 or 2. If the chrome of the material is zero, a 0.100 g sample is used. If <br /> sulfur is not detectable or more accurate values are desired in this sample_ <br /> -�- -� - - size, increase to next highest sample size and rerun. <br /> Read entire manuals on both the Leco Induction Furnace and the Automatic <br /> Titrator. <br /> Periodically clean titration chamber and associated glassware with acetone <br /> or concentrated hydrochloric acid and rinse thoroughly with distilled mater. <br /> 51 . <br />