In the laboratories of the Geological Survey of Sweden we have for many years used an acid-resistant, stainless steel filtering funnel to prepare ‘oriented’ clay mounts for X-ray diffractometry. The funnel consists of three parts (left and centre foreground of Fig. 1). The circular plate is porous and made of sintered stainless steel and serves as a support for a 47 mm diameter membrane filter. The cylinder is manufactured in two different sizes, 250 ml and 600 ml. The funnel is generally mounted on a suction flask but when the filtrate has to be analysed a suction cloche is preferable.

When many mounts have to be prepared the use of a manifold is practical and time saving. We have adapted the Sartorius six-branch manifold and added a transition tube of stainless steel (right foreground of Fig. 1), threaded to fit the manifold outlet and tightened through a gasket. The funnel itself is mounted on the tube through a rubber stopper. Suction is by a small pump (25 l/min, 0·15 kW). A suction flask is placed between the filter stand and the pump to collect the combined filtrates (Fig. 2).