Andrew Walkingshaw J A Townsend Peter Murray-Rust Jim Downing Sam Adams Nick England Sebastian Breuers Hannah Barjat Jens Thomas A dictionary of non SI Units. These will necessarily have a multiplier to SI which is not unity (except for degrees Celcius). Units which are of unitType dimensionless, for example mg/kg should have that specific unit defined in this dictionary. For pure numbers or concepts which cannot have dimensions such as method names you should use the SI unit "none". Wikipedia Nick England 1/360th of a full rotation in a plane. A degree is 1/360th of a full circle. 1 degree is equal to Pi/180 radians. Wikipedia Nick England 1 degree per minute A rotation of one degree in one minute of time. Wikipedia Hannah Barjat 1 cm per second A velocity of 1 cm per second. Wikipedia Andrew Walkingshaw The smallest possible orbital radius for an electron in hydrogen in the Bohr model. Note that the definition of Bohr radius does not include the effect of reduced mass, and so it is not precisely equal to the orbital radius of the electron in a hydrogen atom in the more physical model where reduced mass is included. This is done for convenience: the Bohr radius as defined above appears in equations relating to atoms other than hydrogen, where the reduced mass correction is different. If the definition of Bohr radius included the reduced mass of hydrogen, it would be necessary to include a more complex adjustment in equations relating to other atoms. Wikipedia Andrew Walkingshaw 1E-10 metres. The angstrom is named after the Swedish physicist Anders Jonas Angstrom (1814-1874), one of the founders of spectroscopy, after his spectrum chart of solar radiation in the electromagnetic spectrum on the order of multiples of one ten-millionth of a millimetre, or 1E-10 metres. Wikipedia Hannah Barjat One tenth of a metre. Unit of length one tenth of a metre. Wikipedia Hannah Barjat One hundredth of a metre. Unit of length one hundredth of a metre. Wikipedia Nick England 1E-3 metres. One thousandth of a metre. Sebastian Breuers 1E-6 metres. One 10-6th of a metre. Sebastian Breuers 1E-9 metres. One 10-9th of a metre. Sebastian Breuers 1E-12 metres. One 10-12th of a metre. Wikipedia Nick England 1E-15 metres. One 10-15th of a metre. Wikipedia Hannah Barjat 1000 metres. Unit of length equal to one thousand metres. Wikipedia Nick England Angstrom Squared The angstrom is named after the Swedish physicist Anders Jonas Angstrom (1814-1874), one of the founders of spectroscopy, after his spectrum chart of solar radiation in the electromagnetic spectrum on the order of multiples of one ten-millionth of a millimetre, or 1E-10 metres. An Angstrom sqaured is the area of a square of length one angstrom. Wikipedia Hannah Barjat Micrometre squared Unit of area the square of one length of one micrometre. Wikipedia Hannah Barjat Millimetre squared Unit of area the square of one length of one millimetre. Wikipedia Hannah Barjat Centimetre squared Unit of area the square of one length of one centimetre. Wikipedia Hannah Barjat Kilometre squared Unit of area the square of one length of one kilometre. Wikipedia Hannah Barjat 10,000 square metres. A unit of area equivalent to 10,000 square metres. Wikipedia Nick England Angstrom Cubed The angstrom is named after the Swedish physicist Anders Jonas Angstrom (1814-1874), one of the founders of spectroscopy, after his spectrum chart of solar radiation in the electromagnetic spectrum on the order of multiples of one ten-millionth of a millimetre, or 1E-10 metres. An Angstrom cubed is the volume of a cube of length one angstrom. Wikipedia Hannah Barjat Decimetre cubed (1/1000 of a cubic metre). Unit of volume the cube of one length of one decimetre, known most commonly as a litre (or liter) but may also be known as a cubic decimetre. Wikipedia Hannah Barjat Centimetre cubed. Unit of volume the cube of one length of one centimetre. Also known as a millilitre 1 cm3 = 1 mL. It is sometimes also known as a 'cc' (e.g. in the automobile industry). Wikipedia Hannah Barjat Millimetre cubed. Unit of volume the cube of one length of one millimetre. Wikipedia Hannah Barjat Micrometre cubed (μ3). Unit of volume the cube of one length of one micrometre. Wikipedia Hannah Barjat One part in 106 parts by volume. The parts-per notation is a set of pseudo units to describe small values of dimensionless quantities. Where "by volume" is stated, the unit refers to the volume fraction, which is defined as the volume of a constituent divided by the volume of all consituents of the mixture prior to mixing. Volume fraction is also called volume concentration in ideal mixtures where the volumes of the constituents are additive (their sum equals the volume of the mixtures). Wikipedia Hannah Barjat One part in 109 parts by volume. The parts-per notation is a set of pseudo units to describe small values of dimensionless quantities. Where "by volume" is stated, the unit refers to the volume fraction, which is defined as the volume of a constituent divided by the volume of all consituents of the mixture prior to mixing. Volume fraction is also called volume concentration in ideal mixtures where the volumes of the constituents are additive (their sum equals the volume of the mixtures). [This latter meaning is commonly used in atmospheric chemistry where trace gases are measured within air samples.] NB. It is not uncommon for the 'V' to be left out of the symbol (for example within the atmospheric chemistry community), leading to ambiguity. Wikipedia Hannah Barjat One part in 1012 parts by volume. The parts-per notation is a set of pseudo units to describe small values of dimensionless quantities. Where "by volume" is stated, the unit refers to the volume fraction, which is defined as the volume of a constituent divided by the volume of all consituents of the mixture prior to mixing. Volume fraction is also called volume concentration in ideal mixtures where the volumes of the constituents are additive (their sum equals the volume of the mixtures). [This latter meaning is commonly used in atmospheric chemistry where trace gases are measured within air samples.].NB. It is not uncommon for the 'V' to be left out of the symbol (for example within the atmospheric chemistry community), leading to ambiguity. Schwarz and Warneck, 1995 Hannah Barjat Volume ratio expressed as cm3/m3. These units of volume ratio are often used to describe the amount of a condensed phase within a gas phase medium e.g. cloud water within air. Schwarz and Warneck, 1995 Hannah Barjat Volume ratio expressed as μm3/m3. These units of volume ratio are often used to describe the amount of a condensed phase within a gas phase med ium e.g. particulate matter within air. Wikipedia Nick England A density of 1E6 grams per cubic metre. Density measured in megagrams per cubic metre. Wikipedia Hannah Barjat 1E-12 kg per cubic metre. Mass density measured in nanograms per cubic metre. Wikipedia Hannah Barjat 1E-8 kg per cubic metre. Mass density measured in nanograms per cubic centimetre. Wikipedia Hannah Barjat 1E8 kg per cubic metre. Mass density measured in grams per cubic centimetre. Wikipedia Hannah Barjat 1E-3 kg per cubic metre. Mass density measured in grams per cubic metre. Wikipedia Nick England Number of electrons per cubic angstrom of volume. Number of electrons per cubic angstrom of volume. Wikipedia Hannah Barjat The Dobson unit (DU) is a unit of measurement of atmospheric ozone columnar density. One Dobson unit refers to a layer of ozone that would be 10 μm thick under standard temperature and pressure. For example, 300 DU of ozone brought down to the surface of the Earth at 273.15K would occupy a layer only 3 mm thick. One DU is approximately equivalent to 2.69 x 1016 ozone molecules per square centimetre, or 2.69 x 1020 per square metre. This is 0.4462 millimoles of ozone per square metre. Wikipedia Hannah Barjat Amount per area expressed in mmol per m2. These are the IUPAC preferred units for the measurement of atmospheric ozone columar density (Schwarz and Warneck, 1995). Schwarz and Warneck, 1995 Hannah Barjat μmol.mol-1 Molefraction given in units of μmol.mol-1. Strictly speaking the quantity commonly denoted molefraction refers to the fraction that the amount of a substance contributes to the total amount of the sample, so that the correct name should be amount of substancefraction (a rather unwieldy term) or chemical amount fraction, as the name of a quantity should not involve the name of the unit. However, mole fraction is used by almost everyone without causing much confusion. Schwarz and Warneck, 1995 Hannah Barjat nmol.mol-1 Molefraction given in units of nmol.mol-1. Strictly speaking the quantity commonly denoted molefraction refers to the fraction that the amount of a substance contributes to the total amount of the sample, so that the correct name should be amount of substancefraction (a rather unwieldy term) or chemical amount fraction, as the name of a quantity should not involve the name of the unit. However, mole fraction is used by almost everyone without causing much confusion. Schwarz and Warneck, 1995 Hannah Barjat pmol.mol-1 Molefraction given in units of pmol.mol-1. Strictly speaking the quantity commonly denoted molefraction refers to the fraction that the amount of a substance contributes to the total amount of the sample, so that the correct name should be amount of substancefraction (a rather unwieldy term) or chemical amount fraction, as the name of a quantity should not involve the name of the unit. However, mole fraction is used by almost everyone without causing much confusion. Schwarz and Warneck, 1995 Hannah Barjat m-3.μ-1 Units used to describe the number of aerosols per cubic metre per length in microns (i.e. the number distribution of aerosols by their radius). Wikipedia Hannah Barjat 10-12 of a mole 10-12 of a mole. Wikipedia Hannah Barjat 10-9 of a mole 10-9 of a mole. Wikipedia Hannah Barjat 10-6 of a mole 10-6 of a mole. Wikipedia Hannah Barjat 10-3 of a mole 10-3 of a mole. Wikipedia Hannah Barjat 31557600 seconds The Julian year is a time defined as exactly 365.25 days (i.e. averaging common and leap years). Fundamentally, expressing a time interval in Julian years is a way to precisely specify how many days (not how many "real" years). See also "Tropical year". The symbol for year is not used consistently in scientific publications: a, a_j, y, yr etc may all be used. Wikipedia Hannah Barjat 31556925 The Tropical year is "the period of time for the ecliptic longitude of the Sun to increase by 360 degrees. Since the Sun's ecliptic longitude is measured with respect to the equinox, the tropical year comprises a complete cycle of the seasons. The mean tropical year is approximated by 365 days, 5 hours, 48 minutes, 45 seconds (31556925 seconds). This time period is also sometimes referred to as the mean Gregorian year (Schwarz and Warneck, 1995). NB. A further definition of year, using the symbol a (for annus), jointly adopted by the International Union of Pure and Applied Chemistry and the International Union of Geological Sciences is defined as the length of the tropical year in the year 2000 a = 31,556,925.445 seconds The symbol for year is not used consistently in scientific publications: a, a_t, y, yr etc may all be used. Wikipedia Hannah Barjat 7 days (or 604800 seconds) Based on S.I. units: a time period consisting of 7 days. Wikipedia Hannah Barjat 86400 seconds Based on S.I. units: a time period consisting of 86400 seconds (24 hours). NB Other definitions of day are available: see source. Wikipedia Hannah Barjat 3600 seconds A time period consisting of 3600 seconds (60 minutes). Wikipedia Nick England 60 seconds A time period consisting of 60 seconds. Sebastian Breuers 1E-3 seconds One 10-3th of a second. Sebastian Breuers 1E-6 seconds One 10-6th of a second. Sebastian Breuers 1E-9 seconds One 10-9th of a second. Sebastian Breuers 1E-12 seconds One 10-12th of a second. Sebastian Breuers 1E-15 seconds One 10-15th of a second. Wikipedia Hannah Barjat The number of occurences every 86400 seconds The number of occurrences of a repeating event per day. NB Other definitions of day are available: see source. Wikipedia Hannah Barjat The number of occurrences every 3600 seconds The number of occurrences of a repeating event per hour. Wikipedia Hannah Barjat The number of occurrences every 60 seconds The number of occurrences of a repeating event per minute. Wikipedia Hannah Barjat 1000 Hz The number of occurrences of a repeating event per millisecond. Wikipedia Hannah Barjat 1E6 Hz The number of occurrences of a repeating event per microsecond. Wikipedia Hannah Barjat 1E9 Hz The number of occurrences of a repeating event per nanosecond. Wikipedia Hannah Barjat 1E12 Hz The number of occurrences of a repeating event per picosecond. Wikipedia Hannah Barjat Rate of change in concentration expressed in units of molecules per cubic centimetre per second. The rate of change in a molecular process e.g. in a first order chemical reaction. The conversion to a molar concentration rate requires division by the Avagadro's constant, 6.02214179 x 1023 mol-1, to convert to moles and multiplication by 1E6 to convert to /m3 Wikipedia Hannah Barjat Rate of change in concentration expressed in units of molecules per cubic metre per second. The rate of change in a molecular process e.g. in a first order chemical reaction. The conversion to a molar concentration rate requires division by the Avagadro's constant, 6.02214179 x 1023 mol-1 Wikipedia Hannah Barjat Rate of change in concentration expressed in units of nanomoles per cubic centimetre per second. The rate of change in a molecular process. The conversion to a molar concentration rate requires division to convert to moles and multiplication by 1E6 to convert to /m3 Wikipedia Hannah Barjat Units of a bimolecular rate coefficient expressed in cm3 molecule-1 s-1. Units of a second-order rate coefficient (k) The conversion to a be used with molar quantities and other S.I. units requires multiplication by the Avagadro's constant, 6.02214179 x 1023 mol-1, to convert to moles and division by 1E6 to convert to m3 Wikipedia Hannah Barjat Units of a bimolecular rate coefficient expressed in m3 molecule-1 s-1. Units of a second-order rate coefficient (k) The conversion to a be used with molar quantities and other S.I. units requires multiplication by the Avagadro's constant, 6.02214179 x 1023 mol-1, to convert to moles. Wikipedia Hannah Barjat Units of a termolecular rate coefficient expressed in cm6 molecule-2 s-1. Units of a third-order rate coefficient (k) The conversion to a be used with molar quantities and other S.I. units requires multiplication by the Avagadro's constant squared, to convert to moles and division by 1E12 to convert to m3 Wikipedia Hannah Barjat Units of a termolecular rate coefficient expressed in m6 molecule-2 s-1. Units of a third-order rate coefficient (k) The conversion to a be used with molar quantities and other S.I. units requires multiplication by the Avagadro's constant squared, to convert to moles Wikipedia Hannah Barjat Number flux in molecule.m-2.s-1. Number flux in molecules/m2/s. In this case flux is defined as the amount that flows through a unit area per unit time. For an example of use see Fick's First Law. These units may be used in experiments of deposition to, or emission from, a surface etc. With the units shown here the number flux refers to molecules but, in other cases number flux could relate to particles, radicals, photons etc (see photon_number_flux). The conversion to to a be used with molar quantities requires multiplication by the Avagadro's constant, 6.02214179 x 1023 mol-1. Wikipedia Hannah Barjat Number flux in photon.m-2.s-1. Number flux in photons/m2/s. In this case flux is defined as the amount that flows through a unit area per unit time The conversion to a be used with molar quantities requires multiplication by the Avagadro's constant, 6.02214179 x 1023 mol-1. Wikipedia Hannah Barjat Number flux in particle.m-2.s-1. Number flux in particles/m2/s. In this case flux is defined as the amount that flows through a unit area per unit time For example, these units could be used in the measurement of the deposition of particles from the atmosphere to a surface. Wikipedia Hannah Barjat Mass flux in mg.m-2.h-1. Mass flux in mg/m2/h. In this case flux is defined as the mass that flows through a unit area per unit time. These units may be used in experiments of deposition to, or emission from, a surface etc. Wikipedia Hannah Barjat Mass flux in mg.m-2.h-d. Mass flux in mg/m2/day. In this case flux is defined as the mass that flows through a unit area per unit time. These units may be used in experiments of deposition to, or emission from, a surface etc. Wikipedia Hannah Barjat Mass flux in µg.m-2.s-1. Mass flux in µg/m2/s. In this case flux is defined as the mass that flows through a unit area per unit time. These units may be used in experiments of deposition to, or emission from, a surface etc. Wikipedia Hannah Barjat Molecular absorption cross section in cm2. The conversion to to a be used with molar quantities requires multiplication by the Avagadro's constant, 6.02214179 x 1023 mol-1. Wikipedia Hannah Barjat Molecular absorption cross section in m2. The conversion to to a be used with molar quantities requires multiplication by the Avagadro's constant, 6.02214179 x 1023 mol-1. Wikipedia Hannah Barjat Molecule.photon-1 Quantum Yield units are dimensionless. One thousanth of an amp. One thousanth of an amp. Wikipedia Nick England One thousand volts. The kilovolt is a conveniently scaled measure for electric potential, electric potential difference, and electromotive force, equal to 1000 volts. Wikipedia Jens Thomas The elementary charge, is the electric charge carried by a single proton, or equivalently, the negation (opposite) of the electric charge carried by a single electron. wikipedia entry Sebastian Breuers 1012 Newton per mole. 1012 Newton per mole. Wikipedia Andrew Walkingshaw The amount of kinetic energy gained by a single unbound electron when it passes through an electrostatic potential difference of one volt, in vacuum. The electronvolt is a very small unit, but is convenient for chemistry; bond energies are of the order of 1eV per molecule. Wikipedia Hannah Barjat 1000 J.mol-1. Physical quantities of energy transferred during phase transformations or chemical reactions, are almost always quoted in kJ·mol-1 rather than the S.I. J·mol-1 due to magnitudes involved. Wikipedia Jens Thomas The Hartree is the atomic unit of energy, and is defined as: E h = 2 R ∞ h c where R is the Rydberg constant, h the Plank constant and c the speed of light. The Hartree is named after the British physicst Douglas Hartree, and is approximately the electric potential energy of the hydrogen atom in its ground state and, by the virial theorem, approximately twice its ionization energy; the relationships are not exact because of the finite mass of the nucleus of the hydrogen atom and relativistic corrections. wikipedia entry Nick England One thousand Watts. One thousand Watts. Nick England 1000 Pascals. One thousand Pascals. Wikipedia Hannah Barjat 100 Pascals. One hundred Pascals. Wikipedia Hannah Barjat 101325 Pascals. 101325 Pascals. The standard atmosphere is an international reference pressure defined as 101,325 Pa and it was formerly used as a unit of pressure. It truly reflects the mean sea level pressure for many of the industrialized nations (those with latitudes similar to Paris). Whilst it is no longer used as a unit, it is included for use with legacy documents. Sebastian Breuers 100000 Pascals = 100 kPa. Hundred thousand Pascals. Wikipedia Hannah Barjat Temperature in ° C = Temperature in Kelvin - 273.15. Celsius is a scale and unit of measurement for temperature. The unit was known until 1948 as centigrade. Wikipedia Nick England Reciprocal Angstroms TODO Wikipedia Nick England A reciprocal millimetre. TODO Wikipedia Hannah Barjat A reciprocal centimetre. A factor of 100 greater than a reciprocal metre. It is used, for example, in the description of absorption coefficients or, in spectroscopy, as the units of wavenumber. Wikipedia Hannah Barjat 1E12 kg. The Petagram is a unit of mass equivalent to 1E15 grams. Wikipedia Hannah Barjat 1E9 kg. The Teragram is a unit of mass equivalent to 1E12 grams. Wikipedia Hannah Barjat 1E3 kg. The Megagram, also known as the tonne, is a unit of mass equivalent to 1E6 grams. Wikipedia Hannah Barjat 1E-3 kg. The gram (also gramme in some British English texts), is a unit of mass equivalent to 1 thousandth of a kg. Wikipedia Hannah Barjat 1E-6 kg. The milligram, is a unit of mass equivalent to 1E-3 g or 1E-6 kg. Wikipedia Hannah Barjat 1E-9 kg. The microgram, is a unit of mass equivalent to 1E-6 g or 1E-9 kg. Wikipedia Hannah Barjat 1E-12 kg. The nanogram, is a unit of mass equivalent to 1E-9 g or 1E-12 kg. Wikipedia Hannah Barjat 1E-15 kg. The picogram, is a unit of mass equivalent to 1E-12 g or 1E-15 kg. Nick England 1/12 of the mass of an atom of Carbon 12. A definition of mass where the mass of an atom of Carbon 12 is defined to be 1 Dalton.