Abstract: The ceramic article, after molding and while in a porous condition, is surface hardened not by being placed in a kiln and exposed to high temperatures, but is operatively arranged to have a combustible gas-air mixture pumped under appropriate pressure through the porosity of its molded shape. The exiting gas-air mixture is, according to the present invention, ignited, and this causes the exterior surface of the molded shape to incandesce, with the result that the external surface hardens without causing internal stresses within the article, and also avoids causing differential thermal expansion between the exterior surface and the fiber substance of the article adjacent thereto.

Abstract: To obtain optimum heat transfer from a heat source to an absorption refrigeration cycle refrigerant, use is made of a doughnut-shaped generator or refrigerant holding tank and a heat source in the specific form of a reactor, as described and illustrated in U.S. Pat. No. 3,217,701, wherein the reactor is located in the central opening of the generator so that the heat which it radiates, which is circumferential in nature, effectively transfers to the refrigerant which is in surrounding relation about the reactor.

Abstract: The present invention contemplates a process for producing a reactor cylinder for use in a radiant heater and the reactor cylinder produced by that process. A liquid vehicle is initially prepared including an alumina dispersion, magnesium sulfate, colloidal silica and powdered talc. An antifoam agent may be added. The alumina dispersion includes dispersable alumina in an amount between about 1% and about 5% by weight, an acid in an amount up to about 0.2% by weight and water in an amount between about 10% and about 30% by weight, all calculated as weight percent based on the weight of the liquid vehicle. The alumina dispersion is then further diluted by the addition of water in an amount between about 40% and about 80% by weight. To the diluted alumina dispersion is added magnesium sulfate in an amount up to about 4% by weight, colloidal silica in an amount up to about 10% by weight and powdered talc in an amount between about 0.0001% and about 0.1% by weight.