A column packing has a multiplicity of generally horizontal superposed layers each of which is provided with adjacent pyramidal formations with open pyramidal sides so that at alternating junctions, the flow through the packing layer receives a rotational impetus in opposite senses. The vectoral sums of the rotation cancel out although the local vorticity ensures intimate mixings of the fluids. The pyramids may have triangular, square or rectangular bases and the apexes of an adjacent layer may coincide with the junctions of the bases of the next layer.