Appendix Metrication: Conversion factors, symbols and definitions BASIC SI UNITS physical quantity •ame of unit length metre masa kilogramme time second electric current ampere thermodynamic temperature degree Kelvin luminous intensity candela Symbols for units do not take a plural form. SUPPLEMENTARY UNITS These units are dimensionless. physical quantity name of unit plane angle radian solid angle steradian symbol for unit m kg s A symbol for unit rad sr DERIVED SI UNITS WITH SPECIAL NAMES physical name symbol definition quantity of unit .for unit of unit energy joule j kg m2s -• force newton N kg m s power watt W kg m2 s electric charge coulomb C A s electric potential difference volt V kg m z s electric resistance ohm electric capacitance farad F A 2 s magnetic flux weber Wb kg m 2 s-2A -• = V s inductance henry H kg ni 2 s magnetic flux density tesla T kg s -• A -• : V s m -2 luminous flux lumen lm cd sr illumination lux Ix cd sr m frequency hertz Hz cycle per second customary temperature, t degree Celius øC t/øC: T/øK --273.15 FRACTIONS AND MULTIPI.ES fraction prefix symbol m tdtiple prefix symbol I 10-• deci d 10 deka da 10- 2 cent i c 102 hecto h 10- 3 milli •n 10 • kilo k 10- • micro It 10 • mega M 10 -• nano n 10 • giga G 10 -12 pico p 10 tz tera T 10 -rs femto f 10 -rs atto a Restricted to instances where there is a strongly felt need. EXAMPLES OF OTHER DERIVED SI UNITS physical quantity SI unit symbol for unit area square metre m 2 volume cubic metre m • density kilogramme per cubic metre kg m -• velocity metre per second m s -• angular velocity radian per second rad s -i acceleration metre per second squared m s -2 pressure newton per square metre N m -2 kinematic viscosity, square metre per second m 2 s-• diffusion coefficient dynamic viscosity newton second per square metre N s m -2 electric field strehgth volt per metre V m -• magnetic field strength ampere per metre A m -• luminanee candela per square metre ed m -• 279

280 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS UNITS ALLOWED IN CONJUNCTION WITH SI physical quantity name of unit symbol for unit definition oJ unit length parsec pc 30.87 x 10 • m area hectare ha 104 m 2 volume litre 1 10 pressure bar bar 105 N m -2 mass tonne t 103 kg • 1 Mg kinematic viscosity stokes St 10 -4 m 2 s -• diffusion coefficient dynamic viscosity poise P 10 magnetic flux density gauss G 10 -4 T {magnetic induction) radioactivity curie Ci 37 x 109 s -' energy electronvolt eV 1.6021 x 10 -'9 J time hour h EXAMPLES OF UNITS CONTRARY TO SI, WITH THEIR EQUIVALENTS* physical quantity unit equivalent length angstr6m 10 -•ø m inch 0.0254 m foot 0.3048 m yard 0.9144 m area square inch 645.16 mm 2 square foot 0.092 903 m 2 square yard 0.836 127 m 2 volume cubic inch 1.638 71 X 10 -5 m 3 cubic foot 0.028 316 8 m 3 U.K. gallon 0.004 546 092 m 3 U.S. gallon 0.003 785 41 m • fluid ounce 28.413 1 cm 3 mass pound 0.453 592 37 kg ounce 28.349 5 g dram 1.771 85 g •ain 64.798 9 mg density pound/cubic inch 2.767 99 x 104 kg m ~3 pound/cubic foot 16.0185 kg m -a concentration ounce/gallon 6.236 02 g 1-1 force dyne 10- $ N poundal 0.138 255 N pound-force 4.448 22 N kilogramme-force 9.806 65 N pressure atmosphere 101.325 kN m -2 tort 133.322 N m -2 pound (f)/sq.in. 6894.76 N m -2 = 6.894 76 kN m -2 inch of mercury 3386.39 N m -2 energy erg 10 -7 J therm 105.506 MJ calorie (I.T.) 4.1868 J calorie (15øC) 4.1855 J calorie (thermochemical) 4.184 J B.t.u. 1055.06 J = 1.055 06 kJ foot poundal 0.042 140 1 J foot pound (f) 1.355 82 J power horse power 745.700 W----0.745 700 kW temperature degree Rankine • øK degree Fahrenheit t/øF= •T/øCq- 32 # Fuller lists are to be found in Anderton, P. and Bigg, P. H. Changing to the metric system. 2nd edn. {1967). {H.M. Stationery Office, London•