Anhydrous copper(II) sulphate turns from white to blue; dry cobalt(II) chloride paper turns from blue to pink. Physical test:
. Prevention includes painting, oiling, galvanizing, or sacrificial protection (using a more reactive metal like Zinc). 6. Acids and Bases (Optional/Introductory) Taste sour, turn blue litmus paper red, pH < 7. Form 3 Chemistry Notes Hk Fixed