Copper sulphate is prepared by blowing a current of air through copper scrap and dilute $H_{2}SO_{4}$. Dilute $HNO_{3}$ is also added:

• A
  to oxidise copper to $Cu^{2+}$ which then forms $CuSO_{4}$ with dilute $H_{2}SO_{4}$
• B
  to oxidise $Fe^{2+}$ to iron$(III)$ sulphate,which remains in solution after crystallisation of $CuSO_{4}$
• C
  to speed up the ionisation of $H_{2}SO_{4}$ to give $SO_{4}^{2-}$ ions
• D
  which combines with $H_{2}SO_{4}$ to give a very strong oxidising mixture and oxidises $Cu$ to $Cu^{2+}$