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Encyclopedia > Parts per notation

Parts-per notation is a measure of concentration that is used where low levels of concentration are significant. These types of measurement units are also known as mixing ratios. In chemistry, concentration is the measure of how much of a given substance there is mixed with another substance. ...


This is often used to denote the relative abundance of trace elements in the Earth's crust, trace elements in forensics or other analyses, or levels of pollutants in the environment. A chemical element, often called simply element, is a chemical substance that cannot be divided or changed into other chemical substances by any ordinary chemical technique. ... Pollutants are substances which directly or indirectly damage us or the environment. ...

Contents


Types of Parts-per notations

  • Parts per hundred (denoted by '%' and very rarely 'pph') - denotes one particle of a given substance for every 99 other particles. This is the common percent. 1 part in 102.
  • Parts per thousand (denoted by '‰' [the permille symbol], and occasionally 'ppt') denotes one particle of a given substance for every 999 other particles. This is roughly equivalent to one drop of ink in a cup of water, or one second per 17 minutes. 'Parts per thousand' is often used to record the salinity of seawater. 1 part in 103.
  • Parts per million ('ppm') denotes one particle of a given substance for every 999,999 other particles. This is roughly equivalent to one drop of ink in a 150 litre (40 gallon) drum of water, or one second per 280 hours. 1 part in 106.
  • Parts per billion ('ppb') denotes one particle of a given substance for every 999,999,999 other particles. This is roughly equivalent to one drop of ink in an Olympic-sized swimming pool, or one second per 32 years. 1 part in 109.
  • Parts per trillion ('ppt') denotes one particle of a given substance for every 999,999,999,999 other particles. This is roughly equivalent to one drop of ink in a canal lock full of water , or one second every 320 centuries. 1 part in 1012.
  • Parts per quadrillion ('ppq') denotes one particle of a given substance for every 999,999,999,999,999 other particles. This is roughly equivalent to a drop of ink in a medium-sized lake, or one second every 32,000 millennia. There are no known analytical techniques that can measure with this degree of accuracy; nevertheless, it is still used in some mathematical models of toxicology and epidemiology. 1 part in 1015.

The word hundred can mean: The word form of the number 100 Hundred (division) Hundred (word) This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... A percentage is a way of expressing a proportion, a ratio or a fraction as a whole number, by using 100 as the denominator. ... Cardinal 1000 one thousand Ordinal 1000th Numeral system Factorization Prime Divisor(s) Roman numeral Unicode symbol(s) , , Greek Prefix chilia Latin Prefix milli Binary 1111101000 Octal 1750 Duodecimal 6B4 Hexadecimal 3E8 1000 (one thousand) is the natural number following 999 and preceding 1001. ... A permille or per mille is a tenth of a percent or one part per thousand. ... Salinity is the saltiness or dissolved salt content of a body of water. ... Sea water is water from a sea or ocean. ... One million (1000000), one thousand thousand, is the natural number following 999999 and preceding 1000001. ... The word billion and its equivalents in other languages refer to one of two different numbers, depending on whether the writer is using the long or short scale. ... The numeral trillion refers to one of two number values, depending on the context of where and how it is being used. ... Canal locks in England. ... The quadrillion is a large number which has one of two values depending on how or where it is being used. ... A millennium is a period of time, equal to one thousand years (from Latin mille, thousand, and annum, year). ... Toxicology (from the Greek words toxicon and logos) is the study of the adverse effects of chemicals on living organisms. ... Epidemiologic studies are generally categorized as descriptive, analytic (aiming to examine associations, commonly hypothesized causal relationships), and experimental (a term often equated with clinical or community trials of treatments and other interventions). ...

Caveats

Of all the pp- variants, ppm is by far the one in most common usage; ppb is also sparingly used, while the others are little more than a curiosity.


Although 'ppt' is usually used to denote 'parts per trillion', it is also on occasion used to denote 'parts per thousand'. If there is any chance of ambiguity, one should describe the abbreviation in full.


Users of ppb and beyond should be aware of the intercultural issues of the Long and short scales and the potential for misunderstandings. Long scale is the English translation of the French term échelle longue, which designates a system of numeric names in which the word billion means a million millions. ...


It is a term with several variants in meaning, so the meaning should be made clear if this term is used. In particular, the ratio can be expressed in terms of particles as above, volume (used in particular for gases) or mass. Volume, also called capacity, is a quantification of how much space an object occupies. ... A gas is one of the four main phases of matter (after solid and liquid, and followed by plasma), that subsequently appear as a solid material is subjected to increasingly higher temperatures. ... Mass is a property of a physical object that quantifies the amount of matter it contains. ...


The usage is generally quite fixed inside most specific branches of science, leading some researchers to believe that their own usage (mass/mass, volume/volume or others) is the only correct one. This, in turn, leads them not to specify their usage in their research, and others may therefore misinterpret their results. For example, electrochemists often use volume/volume, while chemical engineers may use mass/mass as well as volume/volume. Many academic papers of otherwise excellent level fail to specify their usage of the part-per notation. The difference between expressing concentrations as mass/mass or volume/volume is quite significant when dealing with gases and it is very important to specify which is being used. It is quite simple, for example, to distinguish ppm by volume from ppm by mass or weight by using ppmv or ppmw. English chemists John Daniell (left) and Michael Faraday (right), both credited to be founders of electrochemistry as known today. ... Chemical engineering is the application of science, in particular chemistry, physics and mathematics, to the process of converting raw materials or chemicals into more useful or valuable forms. ...


Examples of parts per notation

The metric system is the most convenient way to express this since metric units go by steps of ten, hundred and thousand. For example, a milligram is a thousandth of a gram and a gram is a thousandth of a kilogram. Thus, a milligram is a thousandth of a thousandth, or a millionth of a kilogram. A milligram is one part per million of a kilogram thus, one part per million (ppm) by mass is the same as one milligram per kilogram. Just as part per million is abbreviated as ppm, a milligram per kilogram has its own symbolic form -- mg/kg, which unlike ppm is unambiguous. The International System of Units (symbol: SI) (for the French phrase Syst me International dUnit s) is the most widely used system of units. ...

  • By mass:
  • By volume:
    • one millilitre (or cubic centimetre) in a cubic metre (or kilolitre) is 1 ppm by volume. For most gases (those behaving much like an ideal gas) this is numerically equivalent to µmol/mol on the basis of molecules (not atoms). See Avogadro's law.
  • By mass/volume ratio for dilute aqueous solutions (ppm w/v or ppm m/v):
    • 1 litre (L) of water has mass of approximately 1 kg1, so 1 milligram per litre (mg/L) is, loosely speaking, 1 ppm, for small concentrations in a water solution2.
  • By number of particles or moles:
    • one micromole per mole can also be called 1 ppm.
    • one nanomole per mole is 1 ppb.
    • one picomole per mole is 1 ppt.

Mass is a property of a physical object that quantifies the amount of matter it contains. ... The milligram (symbol mg) is an SI unit of mass. ... The international prototype, made of platinum-iridium, which is kept at the BIPM under conditions specified by the 1st CGPM in 1889. ... Mass is a property of a physical object that quantifies the amount of matter it contains. ... The milligram (symbol mg) is an SI unit of mass. ... A tonne (symbol t), sometimes referred to as a metric tonne, is a measurement of weight. ... The millilitre (spelled milliliter in American English and German) is a metric unit of volume that is equal to one thousandth of a litre. ... The cubic meter (symbol m³) is the SI derived unit of volume. ... An ideal gas or perfect gas is a hypothetical gas consisting of identical particles of negligible volume, with no intermolecular forces. ... In 1811 Amedeo Avogadro stated the hypothesis which we now call Avogadros law: (See: this site for an English translation of his 1811 paper). ... Drinking water This article focuses on water as we experience it every day. ... The litre (spelled litre in Commonwealth English and liter in American English) is a unit of volume. ... A girl in a swimming pool full of water Water (from the Old English waeter; c. ... A milligram per litre or milligram per liter (mg/L) is a measurement of concentration used to measure the how many milligrams of a certain substance there are present in one litre of liquid. ... The mole and its simple conversions into different units of measurements. ...

Use

Examples of situations where parts per million are an appropriate measure include:

Natural abundance refers to the prevalence of different isotopes of an element as found in nature. ... Microminerals (also known as trace elements) are micronutrients that are chemical elements. ... Earth cutaway from core to exosphere. ... Pollutants are substances which directly or indirectly damage us or the environment. ...

Inexact analogues

  • one square centimeter in 1000 square feet is about .95 ppm
  • one two-parent, two-child family in a city of about 4 million people is roughly 1 ppm
  • one CD in the 1.57-million disc3 FreeDB catalogue is nearly 2/3 ppm

freedb is a database of compact disc track listings where all the content is under the GNU General Public License. ...

NIST caution

According to the U.S. National Institute of Standards and Technology (NIST) Guide for the Use of the International System of Units (SI), "the language-dependent terms part per million, part per billion, and part per trillion ... are not acceptable for use with the SI to express the values of quantities." NIST's Guide for the Use of the International System of Units (SI) has examples of alternative expressions. Acceptable SI units are: The National Institute of Standards and Technology (or NIST) formerly known as The National Bureau of Standards is a non regulatory agency of the United States Department of Commerce’s Technology Administration. ...


1 millimole/mole = 1 part per thousand


1 micromole/mole = 1 part per million


1 nanomole/mole = 1 part per billion


1 picomole/mole = 1 part per trillion


Notes

  1. Exactly one kg of pure water at maximum density (~4°C) and standard pressure was the definition of a litre from 1901 to 1964; today the litre is defined as exactly 1 dm³, the only distinction being whether the litre is calibrated to the international standard kilogram or to the  international standard meter, which are defined without reference to one another.
  2. Properly speaking it is approximately 1 ppm by mass or by weight in solution. When solids dissolve, they can increase or decrease the total volume they occupy, and even increase or decrease the total volume of the solution. Adding 1 ppm by weight will rarely produce a solution that is 1 ppm by volume to the same precision. The notation ppm w/v or ppm m/v demonstrates the exact nature of the ratio and is therefore the most precise.
  3. The definition given above is that parts per notation refers to numbers of particles (equivalent to moles), but the parts per notation can also be used by mass or volume. Those using the notation need to state their usage to avoid confusion.
  4. In atmospheric chemistry and in air pollution regulations, the parts per notation is commonly expressed with a v following, such as ppmv, to indicate parts per million by volume. This works fine for gas concentrations (e.g., ppmv of carbon dioxide in the ambient air) but, for concentrations of non-gaseous substances such as aerosols, cloud droplets, and particulate matter in the ambient air, the concentrations are commonly expressed as μg/m³ or mg/m³ (e.g., μg or mg of particulates per cubic metre of ambient air).

  Results from FactBites:
 
Concentration - Wikipedia, the free encyclopedia (1905 words)
Parts per million ('ppm') denotes one particle of a given substance for every 999,999 other particles.
Parts per billion ('ppb') denotes one particle of a given substance for every 999,999,999 other particles.
Parts per trillion ('ppt') denotes one particle of a given substance for every 999,999,999,999 other particles.
  More results at FactBites »

 
 

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