Triclinic lattice has one lattice point at the each corner of the unit cell. It has unit cell vectors a≠b≠c and interaxial angles α≠β≠γ≠90°.
Retardation factor, RF, (in planar chromatography) is a ratio of the distance travelled by the centre of the spot to the distance simultaneously travelled by the mobile phase:
The RF value is characteristic for any given compound on the same stationary phase using the same mobile phase for development of the plates. Hence, known RF values can be compared to those of unknown substances to aid in their identifications.
Conversion factor is a fraction that relates one unit to another. Multiplying a measurement by a conversion factor changes the units of the measurement, for example
Gravimetrical factor is stechiometric proportion between molar mass of analyte and molar mass of precipitate in gravimetry.
Chiral centre in organic chemistry is most often an asymmetrically substituted carbon atom (C*).
Picnometer is a special glass flask which is used for determining a relative density of liquids using the weight of a known volume. It usually has a glass faceted cork which is pierced in the centre like a thin capillary through which surplus of liquid runs out.
Absorptance (α) is the ratio of the radiant or luminous flux in a given spectral interval absorbed in a medium to that of the incident radiation. Also called absorption factor.
Acid is a type of compound that contains hydrogen and dissociates in water to produce positive hydrogen ions. The reaction for an acid HA is commonly written:
In fact, the hydrogen ion (the proton) is solvated, and the complete reaction is:
This definition of acids comes from the Arrhenius theory. Such acids tend to be corrosive substances with a sharp taste, which turn litmus red and produce colour changes with other indicators. They are referred to as protonic acids and are classified into strong acids, which are almost completely dissociated in water, (e.g. sulphuric acid and hydrochloric acid), and weak acids, which are only partially dissociated (e.g. acetic acid and hydrogen sulphide). The strength of an acid depends on the extent to which it dissociates, and is measured by its dissociation constant.
In the Lowry-Brønsted theory of acids and bases (1923), the definition was extended to one in which an acid is a proton donor (a Brønsted acid), and a base is a proton acceptor (a Brønsted base). An important feature of the Lowry-Brønsted concept is that when an acid gives up a proton, a conjugate base is formed that is capable of accepting a proton.
Similarly, every base produces its conjugate acid as a result of accepting a proton.
For example, acetate ion is the conjugate base of acetic acid, and ammonium ion is the conjugate acid of ammonia.
As the acid of a conjugate acid/base pair becomes weaker, its conjugate base becomes stronger and vice versa.
A further extension of the idea of acids and bases was made in the Lewis theory. In this, a G. N. Lewis acid is a compound or atom that can accept a pair of electrons and a Lewis base is one that can donate an electron pair. This definition encompasses "traditional" acid-base reactions, but it also includes reactions that do not involve ions, e.g.
in which NH3 is the base (donor) and BCl3 the acid (acceptor).
Generalic, Eni. "Face-centred cubic lattice." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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Periodic Table