an improved compact apparatus for gas - liquid contact and separation by precipitation of solids therein , which essentially comprises a splash separating section , a solid - gas - liquid contact section and a solid depositing section formed in a single reaction vessel , in which gas is blown into the vessel through a gas disperser having a gas outlet opened below the liquid surface in said solid - gas - liquid contact section and caused to undergo contact with the phase of a suspension forcibly circulated from said solid depositing section formed below said solid - gas - liquid contact section , whereby the precipitated solids are prevented from depositing the inner surface of the vessel and other attendant members .