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A primary standard in metrology is a standard that is sufficiently accurate such that it is not calibrated by or subordinate to other standards. Primary standards are defined via other quantities like length, mass and time. Primary standards are used to calibrate other standards referred to as working standards. [1] [2] See Hierarchy of Standards.
A standard solution created from a secondary standard cannot have its concentration accurately known without stoichiometric analysis against a primary standard. An example of a secondary standard is sodium hydroxide, a hydroscopic compound that is highly reactive with its surroundings. The concentration of a standard solution made with sodium ...
An example of a primary standard was the international prototype of the kilogram (IPK) which was the master kilogram and the primary mass standard for the International System of Units (SI). The IPK is a one kilogram mass of a platinum-iridium alloy maintained by the International Bureau of Weights and Measures (BIPM) in Sèvres, France.
The pictogram for harmful substances of the Globally Harmonized System of Classification and Labelling of Chemicals.. The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is an internationally agreed-upon standard managed by the United Nations that was set up to replace the assortment of hazardous material classification and labelling schemes previously used around ...
The relative sensitivity of a given explosive to impact may vary greatly from its sensitivity to friction or heat. Some of the test methods used to determine sensitivity relate to: Impact – Sensitivity is expressed in terms of the distance through which a standard weight must be dropped onto the material to cause it to explode.
Secondary reference standards: Reference standards calibrated against and traceable to primary WHO materials and intended for use in routine tests; Reference reagent: a WHO reference standard, the activity of which is defined by WHO in terms of a unit; For chemical substances some pharmacopoeias [10] use the WHO terms [11]
Adding of an isotopically altered standard to the sample changes the natural isotopic composition of the analyte. By measuring the resulting isotopic composition, it is possible to calculate the amount of the analyte present in the sample. Isotope dilution analysis is a method of determining the quantity of chemical substances. In its most ...
When choosing primary standards in analytical chemistry, compounds with higher equivalent weights are generally more desirable because weighing errors are reduced. An example is the volumetric standardisation of a solution of sodium hydroxide which has been prepared to approximately 0.1 mol dm −3.