the present invention relates to an automatic device for analyzing successive samples which comprises a turning plate provided at its periphery with vertical sockets containing a small tube filled with the sample to be analyzed , a photomultiplier arranged opposite the lateral face of the plate comprising an orifice communicating with the sockets , a first flat seal adapted to be actuated by a ring to be brought into contact with the lateral face of the plate , a second flat seal adapted to be actuated by another ring above the socket and a third seal carried by a movable cradle below the socket .