The present invention provides a process for producing high purity hydromagnesite from a source of magnesium chloride. The process involves preparation of a magnesium chloride brine of a specific concentration and reacting with sodium carbonate, while maintaining the reaction at a specific temperature range to form a hydromagnesite precipitate. The product can be calcined to generate high purity magnesium oxide compounds.

The present invention provides a process for producing high purity hydromagnesite from a source of magnesium chloride. The process involves preparation of a magnesium chloride brine of a specific concentration, which is ammoniated at a specific temperature range, followed by carbonation, while maintaining the reaction at a specific temperature range to form a hydromagnesite precipitate. The product can be calcined to generate high purity magnesium oxide compounds.

The present invention provides a process for producing high purity hydromagnesite from a source of magnesium chloride. The process involves preparation of a magnesium chloride brine of a specific concentration, which is ammoniated at a specific temperature range, followed by carbonation, while maintaining the reaction at a specific temperature range to form a hydromagnesite precipitate. The product can be calcined to generate high purity magnesium oxide compounds.

A p-type oxide which is amorphous and is represented by the following compositional formula: xAO.yCu.sub.2O where x denotes a proportion by mole of AO and y denotes a proportion by mole of Cu.sub.2O and x and y satisfy the following expressions: 0x<100 and x+y=100, and A is any one of Mg, Ca, Sr and Ba, or a mixture containing at least one selected from the group consisting of Mg, Ca, Sr and Ba.

A p-type oxide which is amorphous and is represented by the following compositional formula: xAO.yCu.sub.2O where x denotes a proportion by mole of AO and y denotes a proportion by mole of Cu.sub.2O and x and y satisfy the following expressions: 0x<100 and x+y=100, and A is any one of Mg, Ca, Sr and Ba, or a mixture containing at least one selected from the group consisting of Mg, Ca, Sr and Ba.

A p-type oxide which is amorphous and is represented by the following compositional formula: xAO.yCu.sub.2O where x denotes a proportion by mole of AO and y denotes a proportion by mole of Cu.sub.2O and x and y satisfy the following expressions: 0x<100 and x+y=100, and A is any one of Mg, Ca, Sr and Ba, or a mixture containing at least one selected from the group consisting of Mg, Ca, Sr and Ba.

A p-type oxide which is amorphous and is represented by the following compositional formula: xAO.yCu.sub.2O where x denotes a proportion by mole of AO and y denotes a proportion by mole of Cu.sub.2O and x and y satisfy the following expressions: 0x<100 and x+y=100, and A is any one of Mg, Ca, Sr and Ba, or a mixture containing at least one selected from the group consisting of Mg, Ca, Sr and Ba.

The present application pertains to processes producing oxides using a weak acid intermediate. In one embodiment a material comprising calcium carbonate is reacted with a solution comprising aqueous carboxylic acid to form a gas comprising carbon dioxide and a solution comprising aqueous calcium carboxylate. The solution comprising aqueous calcium carboxylate is reacted with sodium sulfate to form a solution comprising aqueous sodium carboxylate and a solid comprising calcium sulfate. The solution comprising aqueous sodium carboxylate is reacted with sulfur dioxide to form sodium sulfite and an aqueous carboxylic acid. The sodium sulfite is separated from said aqueous carboxylic acid and reacted to form a solid comprising calcium sulfite which is decomposed to form calcium oxide and sulfur dioxide.

Digestion of impure alumina with sulfuric acid dissolves all constituents except silica. The resulting sulfatesaluminum sulfate, ferric sulfate, titanyl sulfate, and magnesium sulfate for alumina contaminated with iron-, titanium-, and/or magnesium-containing speciesremain in solution at approximately 90 C. Hot filtration separates silica. Solution flow over metallic iron reduces ferric sulfate to ferrous sulfate. Controlled ammonia addition promotes hydrolysis and precipitation of hydrated titania from titanyl sulfate that is removed by filtration. Addition of ammonium sulfate forms ferrous ammonium sulfate and ammonium aluminum sulfate solutions. Alum is preferentially separated by crystallization. Addition of ammonium bicarbonate to an ammonium alum solution precipitates ammonium aluminum carbonate which may be heated to produce alumina, ammonia, and carbon dioxide. The remaining iron rich liquor also contains magnesium sulfate. The addition of oxalic acid generates insoluble ferrous oxalate which is thermally decomposed to ferrous oxide and carbon monoxide which is used to reduce the ferrous oxide to metallic iron. Further oxalic acid addition precipitates magnesium oxalate which is thermally decomposed to magnesium oxide.

Digestion of impure alumina with sulfuric acid dissolves all constituents except silica. The resulting sulfatesaluminum sulfate, ferric sulfate, titanyl sulfate, and magnesium sulfate for alumina contaminated with iron-, titanium-, and/or magnesium-containing speciesremain in solution at approximately 90 C. Hot filtration separates silica. Solution flow over metallic iron reduces ferric sulfate to ferrous sulfate. Controlled ammonia addition promotes hydrolysis and precipitation of hydrated titania from titanyl sulfate that is removed by filtration. Addition of ammonium sulfate forms ferrous ammonium sulfate and ammonium aluminum sulfate solutions. Alum is preferentially separated by crystallization. Addition of ammonium bicarbonate to an ammonium alum solution precipitates ammonium aluminum carbonate which may be heated to produce alumina, ammonia, and carbon dioxide. The remaining iron rich liquor also contains magnesium sulfate. The addition of oxalic acid generates insoluble ferrous oxalate which is thermally decomposed to ferrous oxide and carbon monoxide which is used to reduce the ferrous oxide to metallic iron. Further oxalic acid addition precipitates magnesium oxalate which is thermally decomposed to magnesium oxide.