A Simple, Inexpensive Carbonate-Phosphoric Acid Reaction Method for the Analysis of Carbon and Oxygen Isotopes of Carbonates

A simple and inexpensive method for reacting carbonate samples with phosphoric acid for the measurement of stable carbon and oxygen isotope ratios in carbonates is described. The technique is applied to samples taken in a sealed septum tube inside which a small tube is attached using ordinary household glue. The acid is loaded into this small tube. The whole assembly is evacuated and the vessel is tilted so that the acid makes contact with the carbonate. Isotope determinations were made using calcite at 25°C and calcite and dolomite at 50°C. With dolomite, the reaction was complete in 12 h. Measurements of yield and isotope ratios confirm that this method is as good as the traditional method, which uses potentially breakable Pyrex reaction vessels and costly grease or greaseless stopcocks