Thermodynamic analysis and electrochemical investigations were carried out to evaluate the chemistry and electrode kinetics of a molten carbonate based electrochemical carbon meter for monitoring carbon in molten sodium. Based on the results of investigations a procedure was standardized for assembling the cell. The response of the cell thus assembled could be correlated to the carbon activity in sodium. Impedance studies established that mass transfer at iron membrane was the rate limiting step. Meters were extensively tested in both static and dynamic sodium for evaluating the stability and reproducibility in long term conditions. (C) 2011 Elsevier Ltd. All rights reserved.