Of SI units

Physical quantity Name of SI unit Symbol for SI unit Definition... 

Section 2 combines the former separate section on Mathematics with the material involving General Information and Conversion Tables. The fundamental physical constants reflect values recommended in 1986. Physical and chemical symbols and definitions have undergone extensive revision and expansion. Presented in 14 categories, the entries follow recommendations published in 1988 by the lUPAC. The table of abbreviations and standard letter symbols provides, in a sense, an alphabetical index to the foregoing tables. The table of conversion factors has been modified in view of recent data and inclusion of SI units cross-entries for archaic or unusual entries have been curtailed. 

The factor 47reQ arises from the choice of SI units. Since ap has units time , the acceleration is divided by c to convert the units of the denominator to length, as required by the definition of the field. 

TABLE 1-5 Metric Conversion Factors as Exact Numerical Multiples of SI Units... 

For practical engineering purposes, relative density at 15°C (288 K), widely used in countries outside the United States, is considered equivalent to specific gravity at 60°F (288.6 K). With the adoption of SI units, the American Petroleum Institute favors absolute density at 288 K instead of degrees API. 

I have used units likely to be most familiar to the majority of my readers. Although I welcome the increasing use of SI units, many people still use imperial units—they are more familiar with a 1-in. pipe that a 25-mm pipe-... 

Alphabetical List of Units (symbols of SI units given in parentheses)... 

Exceptions to the use of SI units are found in Chapter 10 where we work with molecules instead of moles, and units such as cm-1 for energy are common. We will also find the bar unit for pressure to be very useful as we define standard state conditions, but a pressure of one atmosphere (atm) is still the condition that defines the normal boiling point and the normal freezing point of a liquid. 

The most important document, accompanying a CRM is its certificate. ISO Guide 31 (1981) provides guidance for the establishment of certificates, labeling of CRMs, and certification reports. The certificate contains among other information the certified values and their respective uncertainties. As important as this information is the traceability statement, which defines to what references the CRM is traceable. Ideally, a CRM is traceable to a suitable (combination) of SI units. This is not always possible, so other stated references may appear here. Especially when certifying matrix reference materials, making the measurements traceable to SI does not imply that the CRM is traceable to SI as well. The steps necessary to transform the sample into a state that can be measured may have a serious impact on the traceability of the values, and thus on the traceability statement. 

Bond lengths have usually been, and still often are, measured in angstroms (A) but, with the advent of SI units, the nanometer (10 9 m) and the picometer (10 12 m) are now being used more frequently. In this book we express bond lengths and other molecular dimensions in pi-cometers, which is for many purposes a more convenient unit than the angstrom (1 A = 100 pm). 

Primary methods have the highest metrological qualities, whose operation can be completely described and understood, and for which a complete uncertainty statement can be written down in terms of SI units. Such methods are used by national laboratories participating in the development of a national or international chemical measurement system. 

Two of the three SI base units have in the meantime acquired redefinitions in atomic terms (e.g., the second is now defined as 9 192 631 770 hyperfine oscillations of a cesium atom). However, the definitions (C.2a)-(C.2c) conceal another unfortunate aspect of SI units that cannot be overcome merely by atomic redefinitions. In the theory of classical or quantal electrical interactions, the most fundamental equation is Coulomb s law, which expresses the potential energy V of two charged particles of charge q and 2 at separation R as... 

Several non-SI units persist in modem usage, the most common being listed in Table 1.2. A calculation performed wholly in terms of SI units will be self-consistent. Provided we know a suitable way to interchange between the SI and non-SI units, we can still employ our old non-SI favourites. 

The original solvent polarity scale, known as the E (30) scale, was defined simply as the energy of the longest wavelength adsorption band for the dye, measured in kcalmol-1. This scale has now been revised and normalized because of the introduction of SI units, and Ej is defined in Equation 1.4. 

Although the use of units is heavily emphasized throughout the text, it was decided not to make exclusive use of SI units almost none of the current texts do so, and an informal poll of chemistry teachers showed little interest in making this change. Anyone strongly committed to another view may easily convert the answers to SI units or work the problems in whatever units are desired. The methods of calculation and the analytical approach will not be affected. 

In data books, viscosity may be recorded either in force or mass units. The particular merit of SI units (kg, m, s, N) is that gc = 1 and much confusion can be avoided by consistent use of that system. Some numbers of frequent use in fluid flow problems are... 

In the 1st Edition of this book (1979) it was noted that it should be unnecessary to state that SI units will be used - that will be assumed to be the case. However, even now the Imperial System lingers on in a few isolated outposts. The universal adoption of SI units virtually eliminates the need to include a section on units because there is no question of conversions or explanations of obscure systems. However it is appropriate to make reference to relevant information. 

The basic reference is to ISO 10011 which details all the units, multiples and sub-multiples to be used. The British standard is identical. ASTM gives guidance on the use of SI units in the Form and Style document which refers... 

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