Primary standards are highly accurate, stable, pure substances used as reference points for calibration and measurement, with examples including potassium dichromate and sodium carbonate. Secondary standards, on the other hand, are calibrated instruments or materials that extend the calibration capabilities of primary standards and are easier to handle. They are essential for verifying accuracy in chemical analyses, particularly in pharmaceutical applications.

1. A primary standard is a pure substance or device used as a reference for
calibration and measurement:
 Accuracy: Primary standards are so accurate that they don't need to be calibrated by
other standards.
 Stability: Primary standards are stable and don't react easily with moisture or air, so
their concentration remains constant over time.
 Purity: Primary standards are extremely pure, with a purity of 99.98% or more.
 High molecular weight: Primary standards have a high molecular weight.
 No water of hydration: Primary standards don't have water of hydration.
 Calibration: Primary standards are used to calibrate other standards, known as working
standards.
 Measurement: Primary standards can be measured in terms of mass, time, or length.
Some examples of primary standards include potassium dichromate,
potassium hydrogen iodate, sodium carbonate, and oxalic acid.
Secondary standards are calibrated instruments or reference materials used to calibrate and verify
the accuracy of primary standards or measuring instruments. They are used in smaller labs to
perform external quality control on control materials, which are used to analyze unknown
concentrations of substances.
Here are some things to know about secondary standards:
 Purpose
Secondary standards are used to extend the calibration capabilities of primary standards,
ensuring increased accuracy, expanded energy ranges, and improved spectral ranges.
 Cost and ease of use
Secondary standards are generally less expensive and easier to handle than primary standards.
 Preparation
Secondary standard solutions are typically prepared by dissolving a known mass of the
secondary standard in a suitable solvent and then standardizing the solution using a primary
standard.
 Role in chemical analyses
Secondary standards play a crucial role in ensuring the accuracy of chemical analyses in
pharmaceutical applications.