Abstract: In a thermionic cathode having a planar emissive body and a heating element of pyrolytic graphite which is provided on the side of the emissive body remote from the emissive surface of the emissive body, a uniform temperature distribution adjusts during operation throughout the overall emissive surface when the heating element is planar and the crystallographic c-axis of the pyrolytic graphite extends everywhere normal to the surface of the heating element facing the emissive body. As a result of this the possibility is obtained of realizing a planar, "rapid", induction-free unipotential cathode having a substantially ideal homogeneous temperature distribution.

Abstract: Disclosed are grid electrodes of glassy carbon which have good mechanical and electrical properties and can be manufactured in a simple manner with a great dimensional stability. The grid electrodes may be made by two alternative methods. In one method a body of cured synthetic resin is formed or processed into the shape of the desired electrode, after which it is carbonized. In the second method a preshaped body of cured synthetic resin which is in the unprocessed state, is carbonized after which the resulting glassy carbon body is further processed to the desired electrode, preferably by laser beam cutting.

Abstract: Disclosed is a method of manufacturing a pyrolytic graphite grid electrode in which after formation of the grid, the electrode is annealed at a temperature of 700.degree. to 1200.degree. C in a reactive atmosphere to remove carbon particles adhering to the electrode surface.

Abstract: Method of manufacturing grid electrodes wherein a grid sleeve is produced by depositing pyrolytic graphite on a polished mandril of glassy carbon and provided with apertures by means of the laser beam, then the finished grid is provided, by means of hot gas pyrolysis, with a second layer of highly oriented pyrolytic graphite, and thermally and/or mechanically after-treated at 3000.degree. to 3800.degree. K and 10-500 bar.

Abstract: A foamed synthetic body is impregnated with a resin which can be converted into vitreous carbon by heating, after which by raising the temperature the body is dried and the resin is hardened, after which, if desired, one or more surfaces of the body are again treated with the impregnating agent and the body is then carbonized by further rise in temperature. In order to ensure that the foamed synthetic body remains stable during the whole preparation, the body is soaked with liquid epoxide resin or an aqueous polyvinyl alcohol solution before impregnation.

Abstract: The undulation of hot-moulded glass is avoided when the cooling of the glass edge layers in the first phase of the moulding operation is delayed and is accelerated after completed moulding. This is achieved by using a mould of a glassy carbon having a porous structure. Prior to the moulding, the pores are filled with a gas-forming liquid or a gas. The resulting gas film between the glass and the surface of the mould is removed ater completed moulding. The pores may subsequently be filled with a cooling agent.

Abstract: The invention relates to a cell for, and a method of, measuring the amount of CO in a gas. After CO has been converted by means of I.sub.2 O.sub.5 into CO.sub.2 and I.sub.2, the gas is introduced into an electrolyte solution through an inlet tube which at its orifice is closed by a porous material which acts as a cathode. The iodide produced at the cathode reacts at the anode to form AgI. The cell and the method have important advantages over the known cell and method.