A procedure is described whereby the molybdenum in a 500-ml seawater sample is brought to the surface in 5 min by an adsorbing colloid flotation process which utilizes iron(III) hydroxide, sodium dodecyl sulfate, and air. Statistical studies on a test series for recovery of molybdenum by means of spectrophotometric analysis show a mean recovery of 95.3% and a relative standard deviation of 2.6%.