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The purity determined for an individual product can vary slightly from lot to lot. The percentage grade figures shown in the catalog represent typical purity values, defined as shown. Similarly, catalog figures for physical data, such as melting point, boiling point or refractive index, are typical values, and may not form part of the product specification.
Where possible, products are assigned one of the grades shown here, based on the assays of different lots determined by the method defined on the product specification.
For these grades, the following tolerances apply:
| Grade | Assay Range |
| 99+% | >99.0% |
| 99% | >98.5% |
| 98+% | >98.0% |
| 98% | >97.5% |
| 97+% | >97.0% |
| 97% | >96.0% |
| 96% | >95.0% |
| 95% | >94.0% |
| 94% | >92.5% |
| 90+% | >90.0% |
| Tech. 90% | >88.0% |
| Tech. 85% | >83.0% |
Other numerical grades may apply to specific products. Inorganic materials are often graded on the basis of metals content (metals basis) or rare earth oxides content (REO). While we make every effort to maintain the grades shown in the catalog, we also reserve the right to amend product grades and specifications up or down as dictated by stock availability. If you require confirmation of any product grade, or wish to know the actual purity for material we hold in stock, contact our Technical Service department. For bulk orders we can also supply you with a certificate of analysis with full analytical results for the particular lot number you have purchased.