Abstract: Methods for producing highly pure solutions containing hydrogen fluoride, one or more salts thereof or a mixture of two or more thereof, by adding hydrogen fluoride to at least one anhydrous solvent, wherein the hydrogen fluoride is added to the anhydrous solvent or solvents in the form of a gas or as a liquified gas or as a mixture of gas and liquefied gas. High purity hydrogen fluoride and ammonium fluoride solutions produced by the inventive method are also disclosed.

Abstract: Silicon oxide etching solutions containing the product of at least one bifluoride source compound dissolved in a solvent consisting of at least one carboxylic acid, and further comprising from about 0.5 to about 3 percent by solution weight of hydrofluoric acid and from about 1 to about 5 percent by solution weight of water, wherein the total concentration of bifluoride source compound is between about 1.25 and about 5.0 moles per kilogram of solvent. Methods for selectively removing silicon oxides and metal silicates from metal surfaces are also disclosed.

Abstract: Silicon oxide etching solutions containing the product of at least one bifluoride source compound dissolved in a solvent consisting of at least one carboxylic acid, and further comprising from about 0.5 to about 3 percent by solution weight of hydrofluoric acid and from about 1 to about 5 percent by solution weight of water, wherein the total concentration of bifluoride source compound is between about 1.25 and about 5.0 moles per kilogram of solvent. Methods for selectively removing silicon oxides and metal silicates from metal surfaces are also disclosed.

Abstract: Methods for producing highly pure solutions containing hydrogen fluoride, one or more salts thereof or a mixture of two or more thereof, by adding hydrogen fluoride to at least one anhydrous solvent, wherein the hydrogen fluoride is added to the anhydrous solvent or solvents in the form of a gas or as a liquified gas or as a mixture of gas and liquefied gas. High purity hydrogen fluoride and ammonium fluoride solutions produced by the inventive method are also disclosed.

Abstract: Silicon oxide etching solutions consisting essentially of the product of at least one bifluoride source compound dissolved in a solvent consisting of about 90% to 100% by weight of at least one carboxylic acid and 0 to about 10% by weight water, wherein the total concentration of bifluoride source compound is between about 1.25 and about 5.0 moles per kilogram of solvent. Methods for selectively removing silicon oxides and metal silicates from metal surfaces are also disclosed.

Abstract: Acid etching mixtures having water content, reduced by the addition of fluorosulfonic acid. The preparation and the use of said acid etching mixtures, particularly in etching silicon, are also disclosed.

Abstract: Process for reducing the metal ion content in a chemical compound having a dipole moment or a mixture of two or more thereof to 1 ppb or less by distillation with supply of the energy required for vaporizing the chemical compound or the mixture of two or more thereof in the form of electromagnetic waves having a frequency in the range from 1 MHz to 50 Ghz.

Abstract: In a device for connecting apparatus for withdrawing ultrapure liquids from containers, the connection plate 4 is provided with three bores 5, 6, 7, of which two bores 5, 6 each extend through a socket 8 for vertical pipes. The top plate 9 has an integrated valve body 23 for accommodating at least two valve heads 2, 3 and three bores 10, 11, 12, which are congruent with the bores 5, 6, 7 of the connection plate 4. The bore 12 extends through the valve body 23, and the two other bores 10, 11 terminate, at one end thereof, in pipe sockets 29, 30, which project into the bores 5, 6 of the connection plate 4, and, at the other end thereof, in channels 31, 32, 33, 34 for the ultrapure liquids, which are arranged in the valve body 23 and are interrupted by the valve heads 2, 3.

Abstract: Hydroxylammonium perchlorate is obtained by reacting a perchlorate-free hydroxylammonium salt with a perchlorate ions-donating compound, the reaction being carried out in aqueous solution with the aid of a cation exchanger, in parallel flow or preferably in countercurrent direction. The hydroxylammonium perchlorate is obtained in a high yield and in a high purity. It is suitable as oxidant in fuels.