Prefixes for quantities

Fractional deci (d) centi (c) milli (m) micro (11) nano (n) pico (P) femto (f) atto (atto) 

Multiple deca (d) hecto (h) kilo (k) mega (M) giga (G) tera (T) penta (P) eka (E) 

The following books and reviews provide fuller details of the topics indicated in this chapter. The authors recommendations for excellent introductory and/or reference texts to the topics are indicated with. [For earlier bibliographies see Purification of Laboratory Chemicals, 4th Edn, ISBN 0750628391 (1996, hardback) and 0750637617 (1997, paperback). 

Bailon, G.K. Ehrlich, W. Fung and W. Berthold (Eds), Affinity Chromatography Methods and Protocols, Humana Press, Totowa, 2000. ISBN 0896036944. 

Chaiken, Analytical Affinity Chromatography, CRC Press Inc, Florida, 1987. ISBN 084935658X. 

Handbook of Affinity Chromatography, Marcel Dekker Inc, 2005. ISBN 9780824740573. 

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X 1023 hydrogen atoms), which is written 1.0000 mol H, is the chemical amount of hydrogen atoms in the sample. Take the advice of your instructor on whether to use the formal term. Like any SI unit, the mole can be used with prefixes. For example, 1 mmol = 10 3 mol and 1 pmol = 10 6 mol. Chemists encounter such small quantities when dealing with rare or expensive natural products and pharmaceuticals. 

We shall first review the common units of weight and volume in the metric system and then describe methods of expressing results. The gram (g) is the basic unit of mass and is the unit employed most often in macro analyses. For small samples or trace constituents, chemists use smaller units. The milligram (mg) is 10 g, the microgram (/xg) is 10 g, and the nanogram (ng) is 10 g. The basic unit of volume is the liter (L). The milliliter (mL) is 10" L and is used conunonly in volumetric analysis. The microliter (/xL) is 10 L (10 mL), and the nanoliter (nL) is 10 L (1Q- mL). (Prefixes for even smaller quantities include pico for 10 and femto for 10" .)... 

Table 1 shows some symbols and abbreviations commonly used in analytical chemistry, while Table 2 shows some of the alternative methods for expressing the values of physical quantities and their relationship to the values in SI units. In addition. Table 3 lists prefixes for SI units and Table 4 shows the recommended values of a selection of physical constants. 

Another important measurable quantity is mass, which can be defined as the quantity of matter present in an object. The fundamental SI unit of mass is the kilogram. Because the metric system, which existed before the SI system, used the gram as the fundamental unit, the prefixes for the various mass units are based on the gram, as shown in Table 5.5. 

The SS prefix for an ion indicates that the quantity is the amount due to sea salt, Na" " being used by Granat as the reference sea salt ion. 

The SI system is based on seven fundamental units, or base units, each identified with a physical quantity (Table 1.1). All other units are derived units, combinations of the seven base units. For example, the derived unit for speed, meters per second (m/s), is the base unit for length (m) divided by the base unit for time (s). (Derived units that are a ratio of base units can be used as conversion factors.) For quantities much smaller or larger than the base unit, we use decimal prefixes and exponential (scientific) notation (Table 1.2). (If you need a review of exponential notation, see Appendix A.) Because the prefixes are based on powers of 10, SI units are easier to use in calculations than English units. 

Standard meter bar an unchanging, reproducible quantity 1 meter is the distance traveled by light in a vacuum in 1/299,792,458 of a second. Length is one of the seven fundamental quantities in the SI system (see Table 1.1). All other physical quantities have units that can be derived from these seven. SI is a decimal system. Quantities differing from the base unit by powers of ten are noted by the use of prefixes. For example, the prefix kilo means "one thousand" (10 ) times the base unit it is abbreviated as k. Thus 1 kilometer = 1000 meters, or 1 km = 1000 m. The SI prefixes are listed in Table 1.2. 

Monta.n Wax. An important product of the direct extractive treatment of lignitic coals is montan wax [8002-53-7]. The term montan wax or Bergwachs refers strictiy to the material obtained by solvent extraction of suitable German brown coals. The generic term for similar materials is montana wax. The small quantities made outside Germany are usually referred to as montan, prefixed by the country of origin (see Waxes). 

Since milli is a prefix, it must always precede a quantity. If m is used without another letter, or if the m follows another letter, it stands for the unit meter. If m precedes another letter, it stands for the prefix milli. 

The measurement system that you will most likely encounter is the SI (Metric) system. Each quantity (such as mass and volume) has a base unit and a prefix that modifies the base unit. The prefixes are the same for all quantities and are based on a decimal system. Below are some basic SI units we will introduce others in later chapters ... 

The measurement system that is most widely used in chemistry is the SI system. It incorporates a base unit for the various quantities and then uses prefixes to moderate the value of the base unit. The Unit Conversion Method is a way to generate easily the setup to a problem. Be sure to round off the final answer to the correct number of significant figures and include the units with the final answer. 

The system defines seven base units (Table 1.7), which are independent of each other but which can be combined in various ways to provide a range of derived units (Table 1.8), each one capable of describing a physical quantity. Coherence is maintained in these derived units because no conversion factors are involved at this stage but in order to provide units of convenient size for different applications a series of standard prefixes may be used. These are multipliers used with coherent units to obtain units of alternative size but only one prefix should be used at a time (Table 1.9). 

Chemists routinely measure quantities that run the gamut from very small (the size of an atom, for example) to extremely large (such as the number of particles in one mole). Nobody, not even chemists, likes dealing with scientific notation (which we cover in Chapter 1) if they don t have to. For these reasons, chemists often use a metric system prefix (a word part that goes in front of the base unit to indicate a numerical value) in lieu of scientific notation. For example, the size of the nucleus of an atom is roughly 1 nanometer across, which is a nicer way of saying 1x10- meters across. The most useful of these prefixes are in Table 2-2. 

One reason for the great diversity of units in existence is the fact that quantities of such diverse magnitudes are measured. A general rule is that the unit should be appropriate in magnitude to the quantity being measured. To obtain a dimension of convenient size in SI units, the SI unit is multiplied by a power of 10 and the prefixes listed in Table B.3 are affixed to the unit. 

One of the ways we will learn to express quantities in Chapter 1 is by using prefixes such as mega for million (I06), micro for one-millionth (10-6). and atto for 10-18. The illustration shows a signal due to light absorption by just 60 atoms of rubidium in the cross-sectional area of a laser beam. There are 6.02 X 1023 atoms in a mole, so 60 atoms amount to 1.0 X 10-22 moles. With prefixes from Table 1-3, we will express this number as 100 yoctomoles (ymol) or 0.1 zeptomole (zmol). The prefix yocto stands for I0-24 and zepto stands for 10-21. As chemists learn to measure fewer and fewer atoms or molecules, these strange-sounding prefixes become more and more common in the chemical literature. 

Express the following quantities with abbreviations for units and prefixes from Tables 1-1 through 1-3 ... 

WFor very large or very small quantities, commonly used prefixes represent amounts that vary by three powers of 10, for example, milli, micro, nano, and pico (10 3,10 6,10 9, and 10 l2, respectively). 

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