                                                                    7—10                         1970                60%                                                                       7—10                             
            1%                    7—11                                                                                        7—12                          95%      10—20%                                                                                                                                                  
                                                                                                          7 — 11                     7—12        a                         b        
                      7—13               —    CuSO               Cu2＋                       Cu2＋＋2e－→Cu      Cu     →Cu2＋＋2e－            7—13     
                                         