A visualization study of the diffusion process between two liquids of different densities under microgravity conditions

A microgravity experiment was conducted during flights of the NASA KC-135 aircraft to study how liquids of various densities mix in different gravitational fields. Several chambers, each containing two liquids of different densities separated from each other by a divider, were subjected to gravitational fields of about 1.8 g in the pull-up period of flight and about 0.02 g during the pushover period. During the latter period, the diffusion process was recorded on a video camera. The observations were later compared with those obtained under normal gravity conditions. Under microgravity conditions, the water/water and water/salt water tests showed no mixing. Tests with water/alcohol and water/anti freeze showed significant mixing at microgravity, indicating that the gravitational force at that stage, although small, is still not zero.