Electrostriction of near-critical SF6 in microgravity

We used interferometry to measure the electric-field-induced (i.e., "electr ostrictive") increase of the density of sulfur hexafluoride near its critic al point. The results at the temperatures T-c + 5 mK, T-c + 10 mK, and T-c + 30 mK, with T-c = 319 K, agree with a calculation based on the Clausius-M ossotti relation and the restricted cubic model equation of state. These me asurements were performed in microgravity so that the electrostrictive dens ity changes (less than or equal to 3.5% in this work) would not be complica ted by stratification of the fluid's density induced by the Earth's gravity .