| The key challenge in zone refining is that impurity levels and other process variables vary throughout the ingot. |
| In other cases the binding of impurity cations on to the resin will enable a purer zeolitic product to be obtained. |
| Consequently, the material is embrittled by impurity segregation to interfacial boundaries. |
| These alloys usually contain manganese as an impurity because wrought metal scrap is used in preparing them. |
| In general, it is recommended that a separate crucible be reserved for melting because of the low impurity limits specified for the alloys. |
| Silicon, after iron, is the highest impurity level in electrolytic commercial aluminum. |
