Abstract: A porous inorganic composite semipermeable membrane provided with a support and a separating layer which has pores with an average diameter less than 1 .mu.m and which comprises at least two refractory metal oxides, wherein:the separating layer is composed of grains of a first oxide phase and grains of at least one second oxide which is dispersed over and chemically bonded to the first oxide phase, so as to constitute at least a portion of the free surface of the grains of the first oxide phase and at least a portion of the grain boundaries between the grains of the first oxide phase;the first oxide phase and the second oxide are chosen so that the second oxide slows down diffusion both at the surface and at the grain boundary of the first oxide phase and has low solubility in the first oxide phase; andthe volume of the second oxide lies in the range of 0.1% to 25% of the volume of the first oxide phase.

Abstract: A process is provided for modifying a ceramic ultrafiltration membrane system consisting of a sub-microporous top layer and a microporous inorganic carrier whereby said top layer after modification has reduced pore size and/or is made catalytically active.

Abstract: Preparation of binary membrane ultrafiltration (UF) toplayers (Al.sub.2 O.sub.3 -CeO.sub.2 and Alhd 2O.sub.3 -TiO.sub.2) to make chemically stable UF membranes and/or or catalytically active membranes. Two stable sols are prepared and mixed under controlled conditions and a top layer is prepared on a support under controlled conditions.

Abstract: A sensor is described for determining the oxygen content of a gas with the sensor consisting of a tablet of stabilized bismuth trioxide having electrode coatings on opposite major surfaces. The resistance between the electrode coatings is a measure of an oxygen partial pressure-dependent quantity. The tablet is immersed entirely in the gas to be analyzed so that the nesessity of a reference gas is eliminated.

Abstract: A process for the production of dry, crack-free mechanically and chemically stable, thin, semi-permeable, inorganic membranes by coating a microporous support of sintered metal oxide or metal hydroxide with a stable sol of Boehemite particles and subsequently drying and heating the coated support.