Guide for the Use of the International System of Units (SI)

Guide for the Use of the International System of Units (SI) 
 
viii 
6.2 Rules and style conventions for SI prefixes........................................................................... 13 
6.2.1 Typeface and spacing ................................................................................................... 13 

6.2.2 
Capitalization ................................................................................................................ 14 

6.2.3 
Inseparability 
of prefix and unit .................................................................................... 14 
6.2.4 Unacceptability of compound prefixes ......................................................................... 14 
6.2.5 Use of multiple prefixes ................................................................................................ 14 
6.2.6 Unacceptability of stand-alone prefixes ....................................................................... 14 
6.2.7 Prefixes and the kilogram ............................................................................................. 14 
6.2.8 Prefixes with the degree Celsius and units accepted for use with the SI....................... 15 
7 Rules and Style Conventions for Expressing Values of Quantities .................................................. 15 
7.1 Value and numerical value of a quantity ............................................................................ 15 
7.2 Space between numerical value and unit symbol ............................................................... 16 
7.3 Number of units per value of a quantity ............................................................................. 16 
7.4 Unacceptability of attaching information to units .............................................................. 16 
7.5 Unacceptability of mixing information with units ............................................................. 17 
7.6 Symbols for numbers and units versus spelled-out names of numbers and units ............... 17 
7.7 Clarity in writing values of quantities ................................................................................ 18 
7.8 Unacceptability of stand-alone unit symbols ..................................................................... 18 
 7.9 
 
Choosing 
SI prefixes ......................................................................................................... 18 
7.10 Values of quantities expressed simply as numbers: the unit one, symbol 1 ....................... 19 
7.10.1 Decimal multiples and submultiples of the unit one ........................................... 19 
7.10.2 
%, 
percentage by, fraction ................................................................................... 19 
7.10.3 ppm, ppb, and ppt ................................................................................................ 20 
7.10.4 Roman numerals .................................................................................................. 21 
7.11 Quantity equations and numerical-value equations ............................................................ 21 
7.12 Proper names of quotient quantities ................................................................................... 22 
7.13 Distinction between an object and its attribute ................................................................... 22 
 7.14 
 
Dimension of a quantity .................................................................................................... 22 
8 Comments on Some Quantities and Their Units .............................................................................. 23 
8.1 Time and rotational frequency............................................................................................ 23 
 8.2 
 
Volume ............................................................................................................................... 23 
 8.3 
 
Weight ................................................................................................................................ 23 
8.4 Relative atomic mass and relative molecular mass............................................................. 24 
8.5 Temperature interval and temperature difference............................................................... 24 
8.6 Amount of substance, concentration, molality, and the like............................................... 25 
8.6.1 Amount of substance ........................................................................................... 25 
8.6.2 Mole fraction of B; amount-of-substance fraction of B ...................................... 25 
8.6.3 Molar volume ...................................................................................................... 26 
8.6.4 
 
Molar 
mass ........................................................................................................... 
 27 
8.6.5 Concentration of B; amount-of-substance concentration of B ............................ 27 
8.6.6 Volume fraction of B ........................................................................................... 27 
8.6.7 
 
Mass 
density; density .......................................................................................... 28 
8.6.8 
 
Molality 
of solute B.............................................................................................. 28 
8.6.9 Specific volume ................................................................................................... 28 
8.6.10 Mass fraction of B ............................................................................................... 28 
8.7 Logarithmic quantities and units: level, neper, bel ............................................................. 28 
 8.8 
 
Viscosity 
............................................................................................................................ 30 
 8.9 
 
Massic, 
volumic, areic, lineic ............................................................................................ 30 

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