Changes between Initial Version and Version 1 of Ticket #169, comment 2


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Timestamp:
Nov 12, 2015, 8:59:18 PM (6 years ago)
Author:
Christof Gessner
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  • Ticket #169, comment 2

    initial v1  
     1Collection of arguments and facts:
     2
    13Absorbance is defined as the log of the transmittance. Transmittance is defined as the ratio of received and transmitted radiant flux. As such, Absorbance is a numerical value without a unit.
    24
    35Some numerical scales that are conventionally used are assigned a unit symbol with the value "1", see for example Hounsfield unit "[hnsf'U]". However, such an assignment should only be made when an impact on patient safety is present.
     6
     7Absorbance is not an arbitrary unit - another argument not to use something similar to "A U" here, as it might be misleading and be used with the meaning "arbitrary unit".
     8
     9Reference: http://goldbook.iupac.org/A00028.html
     10
     11IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook.
     12
     13Definition of the quantity absorbance, symbol ''A''
     14Logarithm of the ratio of incident to transmitted radiant power through a sample (excluding the effects on cell walls). Depending on the base of the logarithm a decadic and Napierian absorbance are used. Symbols (for the quantity):  ''A'',  ''A_10'',  ''A_e''. This quantity is sometimes called extinction, although the term extinction, better called attenuance, is reserved for the quantity which takes into account the effects of luminescence and scattering as well.