ABSTRACT

A loss-on-ignition of limestones to 1000° C interrupted at 550° 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 Fe₂O₃ and oxides of sulfur which in turn reacted with CaCO₃ below the intermediate temperature to form CaSO₄ and cause a premature evolution of CO₂. It is necessary to determine sulfate sulfur and total sulfur in the raw sample and sulfate sulfur after loss-on-ignition at 1000° C. In limestones containing one percent or more pyrite, a sulfate determination after ignition at 550° C is necessary in addition to the other three sulfate determinations. These data enable calculation of a true CO₂ value and a single value for all other volatiles gravimetrically in each sample.