Abstract: The invention concerns, among other things, a precipitating chemical for separating preferably hydrocarbons from water, but also for separating other dissolved and/or suspended organic and/or inorganic substances and particles in an associated liquid, including mineral and/or rock particles, heavy metals, salts, phosphorous compounds, alcohols, lipids, aromatics and cellulose. The precipitating chemical is composed of bentonite, preferably sodium montmorillonite; of polymer, preferably of the polyacrylamide type; of sodium polyphosphate and/or lignite; and of water. The chemical is added to and mixed with waste liquid, after which chemical precipitation is activated through the addition of acid or base until the pH-value of the liquid mixture is 4.0 or less, or the pH-value being 8.0 or more. The liquid mixture then rests until the contaminant(s) flakes and separates from the liquid phase of the mixture and is then deposited or floated from the liquid mixture.