Sulphur, table salt and copper sulphate. Sulphur (yellow, S) is a chemical element that forms a yellow crystalline solid. Table salt (white) is a chemical compound of sodium and chloride ions, forming the colourless crystalline solid sodium chloride (NaCl). Copper (II) sulphate (blue, CuSO4) is a chemical compound of copper and sulphate ions. The copper is in its +2 (II) oxidation state. The blue colour is due to the formation of a hydrated complex of the copper ion.
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