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Parts-per notation

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**Group 1: Applications of Parts-per Notation**

– Parts-per notation used in chemistry for dilute solutions
– 1ppm corresponds to 1mg/L in water solutions
– Parts-per notation in physics/engineering for proportional phenomena
– Dimensionless quantities in parts-per notation
– Parts-per notations expressed in various units
– Usage of parts-per notations in different fields

**Group 2: Parts-per Expressions**

– Percent, permille, per10,000, per100,000, permillion, perbillion
– Representation of 1%, 1‰, 1‱, 1 pcm, and 1 ppm
– Equivalents of parts per hundred, thousand, ten thousand, hundred thousand, million, billion
– Specific values and meanings of each parts-per expression

**Group 3: Criticism of Parts-per Notation**

– Parts-per notation not formally part of the International System of Units (SI)
– Use of percent symbol recognized in mathematical expressions
– Annoyance among unit purists regarding parts-per notation
– Problems associated with parts-per notation outlined

**Group 4: Long and Short Scales Impact**

– BIPM suggests avoiding ppb and ppt due to differing values in countries
– NIST’s position on language-dependent terms with SI
– Importance of clarity in using parts-per notation
– Recommendations for standardization in parts-per expressions

**Group 5: Conversion and Specific Notations**

– Mass fraction, mole fraction, volume fraction
– Better to specify units as kg/kg, mol/mol, or m
– Conversion factor between mass fraction of 1ppb and mole fraction of 1ppb is about 4.7 for CFC-11 in air
– Suffix V or v sometimes added for volume fraction (e.g. ppmV, ppbv, pptv)
– SI-compliant expressions
– Notations for dimensionless quantities provided in scientific notation

Parts-per notation (Wikipedia)

In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are parts-per-million (ppm, 10−6), parts-per-billion (ppb, 10−9), parts-per-trillion (ppt, 10−12) and parts-per-quadrillion (ppq, 10−15). This notation is not part of the International System of Units (SI) system and its meaning is ambiguous.

Fluorescein aqueous solutions, diluted from 10,000 to 1 parts-per-million in intervals of 10 fold dilution. At 1 ppm the solution is a very pale yellow. As the concentration increases the colour becomes a more vibrant yellow, then orange, with the final 10,000 ppm a deep red colour.
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