Dielectric constant anomaly of CO near its liquid-vapor critical point

The first observation of the predicted anomaly in the static dielectric constant of a pure fluid near its critical point is reported. This anomaly, not observed to date in nonpolar fluids, is now seen in CO, a polar fluid. The anomalous increase in the dielectric constant, reaches 1×10-3 for fluid with density very close to the critical value. The functional form of the anomaly is consistent with current theoretical predictions.