Primary Standard
A primary standard is a compound of sufficient purity from which a standard solution can be prepared by direct weighing of a quantity of it, followed by dilution to give a defined volume of solution. A primary standard should satisfy the following requirements.
- It must be easy to obtain, to purify, to dry, (preferably at 110-1200C), and to preserve in a pure state.
- It should be unaltered in air during weighing (should not be hygroscopic), oxidized by air or affected by CO2. It should maintain an unchanged composition during storage.
- It should have a high relative molecular mass so that the weighing errors may be negligible.
- The substance must be readily soluble under the conditions in which it is employed.
- The reaction with the standard solution should be stoichiometric and practically instantaneous. The titration error should be negligible or easy to determine accurately by experiment.
- The substance should be capable to being tested for impurities by qualitative and other tests.
0 comments:
Post a Comment