A loss-on-ignition of limestones to 1,000 degrees C. interrupted at 550 degrees C. for an intermediate weighing provided much of the information needed to calculate carbon dioxide gravimetrically but was complicated by the oxidation of pyrite, which is present in small quantities in many limestones. Upon oxidation pyrite formed Fe 2 O 3 and oxides of S which in turn reacted with CaCO 3 below the intermediate temperature to form CaSO 4 and cause a premature evolution of CO 2 . It is necessary to determine sulfate S and total in the raw sample and sulfate S after loss-on-ignition at 1,000 degrees C. In limestones containing 1% or more pyrite, a sulfate determination after ignition at 550 degrees C. is necessary in addition to the other 3 sulfate determinations. These data enable calculation of a true CO 2 value and a single value for all other volatiles gravimetrically in each sample.

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