Abstract: A tubular chamber is divided by a rigid annular partition into two sections. Each section comprises a resilient membrane installed co-axially with the chamber shell with a certain gap relative to the shell to form a cavity communicating with a gas medium source. This cavity accommodates a stationary perforated rigid member installed coaxially with the membrane and the chamber wall to bear the membrane in its extreme expanded state, when no gas medium is supplied into the cavity. When the gas medium is delivered from the source into the cavity, the membranes contract and expand alternately, causing the liquid to move and agitate. An installation for treatment of loose materials is proposed, which is constructed with the use of these liquid-stirring devices.