Abstract: A very efficient method is proposed for extinguishment of fire involving various dangerous materials hardly fire-extinguishable by conventional methods, such as alkali metal peroxides, alkyl aluminum compounds, diketene and calcium carbide or phosphide in contact with water. The method comprises sprinkling, over the burning site of the fire, a silica-based or silica.multidot.alumina-based powder of porous particles having a specified particle diameter and a specified pore diameter, of which the content of silicon dioxide is at least 80% by weight or the total content of silicon dioxide and aluminum oxide is at least 90% by weight. When the burning material is metallic sodium or potassium, the powder sprinkled is a blend of the above mentioned silica-based powder and a powder of sodium chloride or potassium chloride, respectively, so that the fire can be extinguished more rapidly and reliably than in the use of the silica-based powder alone.

Abstract: An efficient fire extinguishing agent is proposed which is suitable for extinguishing fire of a burning metal such as a magnesium powder and used, for example, as a filling of fire extinguishers with stability over a long period of time for storage without decreasing the flowability and ejectability from the extinguisher. The fire extinguishing agent is a powdery blend of (a) 95 to 70% by weight of a high-purity boron oxide powder having a specified high B.sub.2 O.sub.3 purity and a low water content and (b) 5 to 30% by weight of an inorganic powder of spherical particle configuration. Glass beads of a specified particle diameter and silica-alumina-based hollow microspheres serve as the inorganic powder.

Abstract: An efficient method for extinguishing fire of various hardly extinguishable materials is proposed. The method comprises sprinkling, over the burning site of the material, a boron oxide powder having a putity relative to the content of B.sub.2 O.sub.3 of at least 90% by weight and containing water in an amount not exceeding 2% by weight, the particles of the powder having a diameter in the range from 5 .mu.m to 1000 .mu.m. The efficiency of fire extinguishment with the boron oxide powder can be further enhanced by blending the boron oxide powder with a variety of inert inorganic powders.

Abstract: The invention provides an efficient and reliable method for extinguishing fire of a chlorosilane compound, which is a notoriously dangerous inflammable material in respect of the difficulty of extinguishment of fire thereof, by sprinkling a specific porous inert silica based or silica-alumina based powder defined by the content of silica or overall content of silica and alumina as well as various parameters as a powdery material followed by spraying an aqueous solution of sodium chloride, potassium chloride or calcium chloride. The fire extinguishing efficiency can be further enhanced when the sprinkled powder is a blend of the above defined porous powder and a specific silica sand in a specific proportion. When the sprinkled powder is such a binary blend, considerably good results can be obtained even by omitting the step of spraying of the aqueous salt solution.

Abstract: When a liquid chlorosilane compound inadvertently runs out of a container, the liquid must be disposed by absorbing using an absorbent since chlorosilane compounds are generally very dangerous and toxic. Instead of dry sand conventionally used as an absorbent in such a purpose, the invention purposes that a very efficient effect of absorption can be obtained by using a silica-, silica/alumina-based porous ceramic material or a mixture of them as an absorbent without gas evolution in the liquid and with little temperature increase of the liquid when the absorbent material has a specified content of silica or silica/alumina and a pore diameter distribution.

Abstract: The invention provides a rapid and reliable method for extinguishment of fire on a chlorosilane compound such as trichlorosilane which is hardly extinguishable once set on fire by any conventional fire-extinguishing methods. The inventive method comprises sprinkling an inert siliceous powder composed of porous particles of specified silica or silica-alumina content having a specified particle diameter, pore diameter and porosity over the surface of the burning chlorosilane compound. The efficiency of fire-extinguishment can further be enhanced when sprinkling of the porous siliceous powder is followed by spraying of water or a highly halogenated hydrocarbon compound, e.g., monobromo monochloromethane and carbon tetrachloride, over the siliceous powder.

Abstract: Method for detecting crystal defects in semiconductor silicon which comprises treating a preliminarily mirror etched crystal of semiconductor silicon with a detecting solution which is a mixture of about 50% hydrofluoric acid solution and concentrated nitric acid in a ratio of 1000 to 0.1-20 by volume added with an anionic surfactant, and thereafter applying renewedly a mirror etching thereto. Also provided is a detecting solution therefor. Practice of the method causes no occupational disease and no environmental pollution with respect to hexavalent chromium.