Сlean a penny in 60 seconds

Vinegar and salt – and an old copper coin shines like new!

Safe­ty pre­cau­tions

Warn­ing! Only un­der adult su­per­vi­sion.


  • plate;
  • bowl;
  • glass;
  • ta­ble­spoon;
  • vine­gar;
  • ta­ble salt;
  • old cop­per coin.

Step-by-step in­struc­tions

Dis­solve two ta­ble­spoons of ta­ble salt in a glass of vine­gar. Pour the so­lu­tion into a bowl and im­merse an old cop­per coin in it – it bright­ens rapid­ly be­fore your eyes!

Process de­scrip­tion

Old cop­per coins are cov­ered with films of a mix­ture of cop­per(I) ox­ide and cop­per(II) ox­ide. Such films can­not be dis­solved in vine­gar or a so­lu­tion of sodi­um chlo­ride sep­a­rate­ly, but they rapid­ly re­act with a mix­ture of vine­gar and salt. Cop­per(II) ox­ide dis­solves in acetic acid, form­ing cop­per(II) ac­etate:

2CH₃­COOH + CuO → (CH₃­COO)₂Cu + H₂O

And cop­per(I) ox­ide re­acts with sodi­um chlo­ride, form­ing chlo­ride com­plex­es:

Cu₂O + 2Na­Cl + 2CH₃­COOH → 2Na[Cu­Cl₂] + 2CH₃­COONa + H₂O

These pro­cess­es must hap­pen si­mul­ta­ne­ous­ly, so the coin can­not be cleaned by rins­ing first with vine­gar, then with a salt so­lu­tion, or vice ver­sa. Rinse your coin with wa­ter af­ter the ex­per­i­ment to en­sure that it re­tains its shine for a long time!

Many more cool ex­per­i­ments await you in the MEL Chem­istry sub­scrip­tion!