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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 ...
Secondary chemical reference substance: substance whose characteristics are assigned and/or calibrated by comparison with a primary chemical reference substance. The United States National Institute of Standards and Technology (NIST) uses the trade marked term [12] Standard Reference Material (SRM) to denote a certified reference material that ...
Titration (also known as titrimetry [1] and volumetric analysis) is a common laboratory method of quantitative chemical analysis to determine the concentration of an identified analyte (a substance to be analyzed). A reagent, termed the titrant or titrator, [2] is prepared as a standard solution of known concentration and volume.
Reagents are "substances or compounds that are added to a system in order to bring about a chemical reaction or are added to see if a reaction occurs." [1] Some reagents are just a single element. However, most processes require reagents made of chemical compounds. Some of the most common ones used widely for specific reactive functions are ...
Primary is a term used in organic chemistry to classify various types of compounds (e.g. alcohols, alkyl halides, amines) or reactive intermediates (e.g. alkyl radicals, carbocations). Red highlighted central atoms in various groups of chemical compounds.
A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. [1] [2] Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combined without reacting, they may form a chemical mixture. [3]
The SI system after 1983, but before the 2019 revision: Dependence of base unit definitions on other base units (for example, the metre is defined as the distance travelled by light in a specific fraction of a second), with the constants of nature and artefacts used to define them (such as the mass of the IPK for the kilogram).