Abstract: A method and a device for converting and separating substances dissolved in a carrier fluid, more particularly proteides or proteins, by adding and mixing with an agent, e.g. enzymes, which brings about the chemical reaction or the build-up or breakdown of the molecules of the substances and causes them to precipitate. In addition these substances are mixed and come to an accelerated reaction with the agent in at least one circuit flow through a jet immersion reactor while a gas is supplied intensively thereto before froth flotation of the precipitated substances is carried out after adding means assisting flotation.