sub calc_enthalpy   {

                      my ($hash, $enthalpy_hash) = @_;
                      my (@common, @total);

                             foreach (keys %$enthalpy_hash)      {


                                      if (exists $hash->{$_})    {
                                              push @common, "$_ = ", $enthalpy_hash->{$_} * $hash->{$_}, "\n";
                                              push @total, $enthalpy_hash->{$_} * $hash->{$_}, "\n";
                                       }

                                    return (\@common, \@total);

                             }

   }