What is the Difference Between Primary and Secondary Standard Solution?

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The main difference between primary and secondary standard solutions lies in their purity and reactivity:

  • Primary Standard Solution: These solutions are made from primary standard substances, which are highly pure (99.9% pure) and have less reactivity. Primary standard solutions are used to standardize secondary standards and other reagents. They have established methods for confirming their purity, atmospheric stability, and modest cost.
  • Secondary Standard Solution: These solutions are less pure and have higher reactivity compared to primary standard solutions. Secondary standard solutions are used for specific analytical experiments and are often standardized against a primary standard. They are typically used to calibrate analytical equipment and analytical techniques.

Primary standard solutions are used as reference materials in titrations and for other quantitative analyses, while secondary standard solutions are used for specific analytical experiments and are generally less pure than primary standard solutions.

Comparative Table: Primary vs Secondary Standard Solution

The main difference between primary and secondary standard solutions lies in their purity and reactivity. Here is a table comparing the two:

Primary Standard Solution Secondary Standard Solution
High purity, typically 99.9% pure Lower purity, not as pure as primary standards
Less reactivity Higher reactivity
Used for standardization of secondary standard solutions and other reagents Used for specific analytical experiments
Examples include potassium bromate (KBrO3), sodium chloride, and zinc powder Examples include sodium thiosulfate (for iodine titrations) and hydrochloric acid (for sodium hydroxide titrations)

Primary standard solutions are made from primary standard substances, which have a high purity and are less reactive. They are used to standardize secondary standard solutions and other reagents. On the other hand, secondary standard solutions are made from secondary standard substances and are used for specific analytical experiments. They have a lower purity compared to primary standard solutions.