supernatant

Allow to stand twenty-four hours, then centrifugalise thoroughly and decant the supernatant fluid into a well-stoppered bottle.

Again remove the supernatant fluid and fill in a fresh supply of saline solution and centrifugalise once more.

Examine a drop of the supernatant opalescent emulsion microscopically to determine its freedom from clumps and masses.

Pipette off all the supernatant fluid and invert the tube to drain on to a pad of sterilised cotton-wool, contained in a beaker.

The liquid is now allowed to settle, and the clear supernatant solution is poured back again into the battery cells.