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  2. Amount of substance - Wikipedia

    en.wikipedia.org/wiki/Amount_of_substance

    Historically, the mole was defined as the amount of substance in 12 grams of the carbon-12 isotope.As a consequence, the mass of one mole of a chemical compound, in grams, is numerically equal (for all practical purposes) to the mass of one molecule or formula unit of the compound, in daltons, and the molar mass of an isotope in grams per mole is approximately equal to the mass number ...

  3. Calibration - Wikipedia

    en.wikipedia.org/wiki/Calibration

    The formal definition of calibration by the International Bureau of Weights and Measures (BIPM) is the following: "Operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties (of the calibrated instrument or ...

  4. High-performance liquid chromatography - Wikipedia

    en.wikipedia.org/wiki/High-performance_liquid...

    A modern self-contained HPLC Schematic representation of an HPLC unit (1) solvent reservoirs, (2) solvent degasser, (3) gradient valve, (4) mixing vessel for delivery of the mobile phase, (5) high-pressure pump, (6) switching valve in "inject position", (6') switching valve in "load position", (7) sample injection loop, (8) pre-column (guard column), (9) analytical column, (10) detector (i.e ...

  5. Total dissolved solids - Wikipedia

    en.wikipedia.org/wiki/Total_dissolved_solids

    Bottled mineral water usually contains higher TDS levels than tap water.. Total dissolved solids (TDS) is a measure of the dissolved combined content of all inorganic and organic substances present in a liquid in molecular, ionized, or micro-granular (colloidal sol) suspended form.

  6. Chemical substance - Wikipedia

    en.wikipedia.org/wiki/Chemical_substance

    Colors of a single chemical in different solvents, under visible and UV light, showing how the chemical interacts dynamically with its solvent environmentIn addition to the generic definition offered above, there are several niche fields where the term "chemical substance" may take alternate usages that are widely accepted, some of which are outlined in the sections below.

  7. pH - Wikipedia

    en.wikipedia.org/wiki/PH

    In chemistry, pH (/ p iː ˈ eɪ tʃ / pee-AYCH), also referred to as acidity or basicity, historically denotes "potential of hydrogen" (or "power of hydrogen"). [1] It is a logarithmic scale used to specify the acidity or basicity of aqueous solutions.

  8. Mass flow rate - Wikipedia

    en.wikipedia.org/wiki/Mass_flow_rate

    Mass flow rate is defined by the limit [3] [4] ˙ = =, i.e., the flow of mass m through a surface per unit time t.. The overdot on the m is Newton's notation for a time derivative. ...

  9. Volume - Wikipedia

    en.wikipedia.org/wiki/Volume

    On 7 April 1795, the metric system was formally defined in French law using six units. Three of these are related to volume: the stère (1 m 3) for volume of firewood; the litre (1 dm 3) for volumes of liquid; and the gramme, for mass—defined as the mass of one cubic centimetre of water at the temperature of melting ice. [10]