Strontium carbonate

Strontium carbonate (SrCO3) is the carbonate salt of strontium that has the appearance of a white or grey powder. It occurs in nature as the mineral strontianite. Strontium carbonate (SrCO3) is the carbonate salt of strontium that has the appearance of a white or grey powder. It occurs in nature as the mineral strontianite. Other than the natural occurrence as a mineral, strontium carbonate is prepared synthetically in one of two processes, both of which start with naturally occurring celestine, a mineral form of strontium sulfate (SrSO4). In the 'black ash' process, celesite is roasted with coke at 110–1300 °C to form strontium sulfide. The sulfate is reduced, leaving the sulfide: A mixture of strontium sulfide with either carbon dioxide gas or sodium carbonate then leads to formation of a precipitate of strontium carbonate. In the 'direct conversion' or double-decomposition method, a mixture of celesite and sodium carbonate is treated with steam to form strontium carbonate with substantial amounts of undissolved other solids. This material is mixed with hydrochloric acid, which dissolves the strontium carbonate to form a solution of strontium chloride. Carbon dioxide or sodium carbonate is then used to re-precipitate strontium carbonate, as in the black-ash process. It is widely used in the ceramics industry as an ingredient in glazes. It acts as a flux and also modifies the color of certain metallic oxides. It has some properties similar to barium carbonate. Strontium carbonate is also used for making some superconductors such as BSCCO and also for electroluminescent materials where it is first calcined into SrO and then mixed with sulphur to make SrS:x where x is typically europium.This is the famous 'blue/green' phosphor which is sensitive to frequency and changes from lime green to blue.Other dopants can also be used such as gallium, or yttrium to get a yellow/orange glow instead. Because of its status as a weak Lewis base, strontium carbonate can be used to produce many different strontium compounds by simple use of the corresponding acid. The cyanobacteria, Calothrix, Synechococcus and Gloeocapsa, can precipitate strontian calcite in groundwater. The strontium exists as strontianite in solid solution within the host calcite with the strontium content of up to one percent.