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CO 2 coulometry is a rapid, highly accurate technique which can be used to determine the carbonate carbon contents of coals and associated overburdens. The rate at which the co 2 is evolved during the acid digestion process is a function of which carbonate phases are present. Calcite and dolomite reaction times are approximately six to eight minutes under the conditions described herein, with the maximum change in reaction rates occurring between two and four minutes. Siderite requires a lengthy 10 to 15 minutes to completely react with the maximum change in reaction rate occurring between six and eight minutes. The determination of neutralization potential (NP) in the coal-bearing overburdens of the eastern United States is inaccurate when sideri t$ is pres~nt because of the slow conversion of Fe2 to Fe3. To alleviate the effects of siderite on NP, a 30 wt.% H 2 0 2 solu}ion can be used to accelerate the conversion of Fe2 to Fes+ during the titration process. The addition of H 2 0 2 increases both the accuracy and precision of the NP determination. Despite the addition of H 2 o 2 , many siderite-bearing overburdens still possess NP. This is interpreted as being the result o~: 1) the incomplete oxidation of Fe2+ to Fe3 and the incomplete precipitation of iron hydroxide, and/or 2) the presence of Ca and/or Mg occurring in solid solution in the siderite.

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