A reference material is a material or substance that has one or more sufficiently uniform and well defined properties for the purpose of calibrating a measuring device, evaluating a measurement method, or assigning a value to a material. Reference materials for harmonizing quantity values include reference materials for chemical composition analysis, reference materials for measurement of physical and physicochemical properties, and reference materials for measurement of engineering and technical properties.

A reference substance is a substance used in analytical chemistry to directly prepare a standard solution or to calibrate the concentration of a manipulated solution in titration analysis. It has been widely used in the fields of chemical measurement, biological measurement, engineering measurement and physical measurement, is an important part of stoichiometry and an important means of quantity transmission and traceability, and is widely used in all aspects of national economy and social development.

The reference material should meet five requirements:

1, purity (mass fraction) should be ≥99.9%;

2, the composition is completely consistent with its chemical formula, such as containing crystal water, the content of crystal water should be in line with the chemical formula;

3, stable nature, under normal circumstances is not easy to lose water, water absorption or deterioration, does not react with oxygen and carbon dioxide in the air;

4, when participating in the reaction, it should be carried out quantitatively according to the reaction formula, there is no side reaction;

5, to have a large molar mass, in order to reduce the relative error when weighing.

The standard substances are not necessarily the reference substances, because the standard substances are only known content, the purity may not reach 99.9%, most of the standard substances are customized by qualified units, and some have unified numbers.

The reference material is high enough in itself and stable in nature. The solution can be directly prepared and the concentration of the unknown solution can be calibrated.

The role of the reference substance is to:

1, save and transfer the characteristic value, establish the measurement traceability

2. Ensure the consistency and comparability of measurement results

3. Research and evaluation of measurement methods

4. Ensure the smooth conduct of product quality supervision and inspection

The above content is the introduction of the difference between the standard substance and the reference substance, the standard substance is a substance with a standard value and uncertainty, marking the expiration date, and it is a preparation completed. Reference substances play an important role in the development of product assurance verification and implementation, in the quality control and evaluation of product inspection and certification bodies, and in the use room accreditation work.