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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 ...
The process steps may be sequential in time or sequential in space along a stream of flowing or moving material; see Chemical plant. For a given amount of a feed (input) material or product (output) material, an expected amount of material can be determined at key steps in the process from empirical data and material balance calculations.
The process of separating the component substances of a liquid mixture by exploiting differences in the relative volatility of the mixture's components through selective boiling and subsequent condensation. The apparatus used to distill a substance is called a still, and the re-condensed substance yielded by the process is called the distillate.
The centrifugation method has a wide variety of industrial and laboratorial applications; not only is this process used to separate two miscible substances, but also to analyze the hydrodynamic properties of macromolecules. [4] It is one of the most important and commonly used research methods in biochemistry, cell and molecular biology.
Making a saline water solution by dissolving table salt in water.The salt is the solute and the water the solvent. In chemistry, a solution is defined by IUPAC as "A liquid or solid phase containing more than one substance, when for convenience one (or more) substance, which is called the solvent, is treated differently from the other substances, which are called solutes.
The primary r-process has been confirmed by astronomers who had observed old stars born when galactic metallicity was still small, that nonetheless contain their complement of r-process nuclei; thereby demonstrating that the metallicity is a product of an internal process. The r-process is responsible for our natural cohort of radioactive ...
The standard state of a material (pure substance, mixture or solution) is a reference point used to calculate its properties under different conditions.A degree sign (°) or a superscript Plimsoll symbol (⦵) is used to designate a thermodynamic quantity in the standard state, such as change in enthalpy (ΔH°), change in entropy (ΔS°), or change in Gibbs free energy (ΔG°).