DETERMINATION OF THE MOLAR ABSORPTIVITY OF DISSOLVED CARBONATE IN BASANITIC GLASS

Basanitic glasses with known dissolved C concentrations have been anal yzed using infrared spectroscopy to calibrate the molar absorptivity o f carbonate. C is dissolved as carbonate complexes in the glass result ing in absorption bands at 1525 and 1425 cm(-1). Molar absorptivities of 283 +/- 8 L/(mol . cm) were determined for both 1525 and 1425 cm-l absorption bands. An integrated molar absorptivity of 60000 +/- 1700 L /(mol . m(2)) was determined using the integrated area under the doubl et. These values are about 20-25% lower than those determined for thol eiitic and leucititic glasses and are intermediate between values char acteristic of Na- and Ca-rich silicate glasses. Carbonate molar absorp tivities for a range of basaltic glass compositions correlate with the molar ratio of Na/(Na + Ca).