Secondary Standard
Definition and meaning of Secondary Standard in chemistry.
A secondary standard is a chemical substance whose concentration is accurately determined by titrating it against a verified primary standard. It is commonly used as a working reference material for volumetric analysis after this initial standardization process is complete.
In more detail
Secondary standards are typically less pure, more reactive, or less stable over time than primary standards, meaning their exact concentration must be established immediately before use in quantitative analysis. Despite these limitations, they are often more practical, significantly cheaper, and easier to handle for routine laboratory work than their primary counterparts. For example, sodium hydroxide solutions rapidly absorb water and carbon dioxide gas from the ambient air, altering their molarity, and therefore cannot be used as primary standards; they must be standardized against a stable acid like potassium hydrogen phthalate first.
Key facts
| Field | Analytical Chemistry |
|---|---|
| Formula | NaOH |
| Purpose | Standardization of titrants |
| Requirement | Must be standardized before use |
A prepared aqueous solution of sodium hydroxide is a secondary standard when its exact concentration is confirmed by titrating it against potassium hydrogen phthalate.
Frequently asked questions
Why use a secondary standard instead of a primary one?
They are often cheaper, more readily available, and easier to prepare in large volumes for routine daily laboratory use after the initial standardization.