THE EFFECT OF TIME, ADDITIVES AND METHOD OF MEASUREMENT ON SULFATE DURING THE SELECTIVE OXIDATION OF COAL WITH PERCHLORIC-ACID

A reaction scheme, developed at the Ames Laboratory, for the determina tion of the sulfur forms in coal takes advantage of the selective oxid izing power of perchloric acid. Sulfate, pyritic and organic sulfur ar e removed sequentially from a single sample of coal by solutions of pe rchloric acid boiling at 120, 155 and 205-degrees-C, respectively, and converted to sulfate for subsequent turbidimetric measurement. Work i n this paper focused on improving the selectivity by trying to remove pyrite at lower temperatures and improving the low sulfur recoveries o bserved for some coals. The results indicated that pyritic sulfur can be removed at lower temperatures and that possibly two different forms of organic sulfur can be delineated. After several potential explanat ions for the low sulfur recoveries had been explored, a standard addit ions technique, when applied to the turbidimetric measurement of sulfa te, alleviated the problem of low sulfur recoveries.