Examples of Coprecipitation Reactions

Mucci and Morse (1989) have reviewed much of the research on coprecipitation reactions with calcite and aragonite, and the interested reader is referred to their paper for a detailed discussion of this literature. Here we present examples of the complex coprecipitation behavior of some of the most important ions in natural systems with carbonate minerals. The ions that we have selected are Mg2+, Sr2+, Na+, Mn2+, and SO42-. 

The study of the coprecipitation of Mg2+ in calcite has been an active area of research, frequently marked by controversy over experimental results and their applicability to natural systems. The literature on this topic is prolific, and we will not attempt to review all of it (for a general review see Mackenzie et al 1983). The literature is divided into studies where direct measurement of the solids formed from solutions have been made, studies where properties of the solids have been inferred from their interactions with solutions (e.g., Schoonmaker et al 1982), and papers where authors have estimated values of the partition coefficient by deduction (e.g., Lahann and Seibert, 1982 Given and Wilkinson, 1985a). Here the discussion will be confined to the experimental studies where the compositions of the solids have been directly determined. 

Method Reference Nuclei Time to Precipitate Oc % MgC03  

HCOj +CO -added (3 runs) glass dust et cetera -10 min 120-180 17-18 Bemer (1978) 

HCC 3 +C032 +water soluble extract of marine grass added (2 runs) overnight 170 16-17 Bemer (1978) 

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