CLA Next Stage Steps, page-164

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Cobalt compounds are widely used to make coloring materials. The following compounds are used to color glass, glazes, cosmetics, paints, rubber, inks, and pottery: cobalt oxide, or cobalt black (Co₂O₃); cobalt potassium nitrite, or cobalt yellow (CoK₃(NO₂)₆)); cobalt aluminate, or cobalt blue (Co(AlO₂)₂); and cobalt ammonium phosphate, or cobalt violet (CoNH₄PO₄).
Another important use of cobalt compounds is as catalysts. A catalyst is a substance used to speed up or slow down a chemical reaction. The catalyst does not undergo any change itself during the reaction. Cobalt molybdate (CoMoO₄) is used in the petroleum industry to convert crude oil to gasoline and other petroleum products. It is also used to remove sulfur from crude oil.