What are primary and secondary standard solutions

Dear student,

Primary standard solution:

• Primary standard is a reagent which is generally representative of the number of substance contains and easily weighed. very pure, moles the
• A Primary standard is a reagent that’s stable, it’s not a hydrate /has no water of hydration, and has a high molecular weight.
• Primary standards are typically used in titration to determine an unknown concentration and in other analytical techniques.
• High level of purity, low reactivity (high stability), high equivalent weight (to reduce error from mass measurements)
• Not hygroscopic (to reduce changes in mass in humid versus dry environments), non-toxic, inexpensive and readily available
• It should have a high relative molecular weight so that weighing errors may be negligible.
• The substance should be readily soluble under the conditions in which it is employed.

Secondary standard solution

• Secondary standard is a chemical that has been standardized against a primary standard for use in a specific analysis. Secondary standards are commonly used to calibrate analytical methods.
• A secondary standard is a substance which may be used for standardization
• A secondary standard is a standard that is prepared in the laboratory for a specific analysis. It is usually standardized against a primary standard.
• It follows that a secondary standard solution is a solution in which the concentration of dissolved solute has not been determined from the weight of the compound dissolved but by reaction (titration) of a volume of the solution against a measured volume of a primary standard solution.
• A secondary standard is a chemical or reagent which has certain properties such as:-

1. It has less purity than primary standard
2. Less stable and more reactive than primary standard But its solution remains stable for a long time
3. Titrated against primary standard