supernatant

adj

1. (not-comparable)Lying or floating above a denser fluid, or above a solid sediment or precipitate (which has been separated by crystallisation, centrifugation etc.).

   “There may be a place at some certain latitude between the poles and the line on each side the equator, where the inflammable supernatant atmosphere may end, owing to the greater centrifugal force of the heavier aerial atmosphere.”

noun

1. The liquid that lies above a sediment or precipitate.
2. Material that floats on the surface of a liquid.