The feasibility of an electrochemical carbon meter which measures the chemical activity of carbon in sodium at temperatures from 600 to 700°C has been demonstrated. The meter is based on the cell and has been shown to respond to the addition of various carbonaceous reagents that were added to the sodium, especially carburized iron. The chemical activity of carbon in equilibrium with a 347 stainless-steel sodium system has been measured The meter can be used to indicate when carburizing or decarburizing conditions exist in the sodium. The solubility of carbon in sodium has been determined with the carbon meter.