Practical steps for improved estimates of calcium carbonate concentrations in deep sea sediments using coulometry

Coulometric titration is a commonly used method for determination of carbonate carbon, and hence calcium carbonate concentrations, in geological materials. Analyzes of 460 samples of pure CaCO 3 powder demonstrate that the coulometer output data need to be recalculated using a multi‐point regression analysis. These analyses also demonstrate that to generate a precision of ±0.8%, at least 7 mg of 100% calcite is needed. A precision of ± 0.5% requires 12 mg pure calcite. We recommend that 35 mg samples are used for most deep sea sediment samples, which gives a precision of ±0.8% down to 20% calcite contents in the sample. Calcite contents <10% in samples require multiple runs to improve precision.