Changes between Initial Version and Version 1 of Ticket #5775


Ignore:
Timestamp:
Sep 16, 2020, 5:57:29 PM (3 months ago)
Author:
Gunther Schadow
Comment:

Legend:

Unmodified
Added
Removed
Modified
  • Ticket #5775 – Description

    initial v1  
    33A needed change to a couple of UCUM constants:
    44
    5 In 2019 the definition of “mole” was revised (https://en.wikipedia.org/wiki/2019_redefinition_of_the_SI_base_units#Mole) to be exactly 6.02214076×1023 (instead of being experimentally determined), but UCUM has an older value of 6.0221367×1023.
     5In 2019 the definition of “mole” was revised (https://en.wikipedia.org/wiki/2019_redefinition_of_the_SI_base_units#Mole) to be exactly 6.02214076×10^23^ (instead of being experimentally determined), but UCUM has an older value of 6.0221367×10^23^.
    66
    7 Also, the conversion of an atomic mass unit to g (experimentally determined) needs an update.  Per the 2018 CODATA recommendations (https://physics.nist.gov/cuu/pdf/wallet_2018.pdf) the recommended value is now 1.660 539 066 60(50) × 10−24 g.  UCUM has 1.6605402 × 10-24.  Note that the “(50)” is the uncertainty on the previous two digits and should not be included in the value.
     7Also, the conversion of an atomic mass unit to g (experimentally determined) needs an update.  Per the 2018 CODATA recommendations (https://physics.nist.gov/cuu/pdf/wallet_2018.pdf) the recommended value is now 1.660 539 066 60(50) × 10^−24^ g.  UCUM has 1.6605402 × 10^-24^.  Note that the “(50)” is the uncertainty on the previous two digits and should not be included in the value.
    88
    99The re-definition of a mole as a number affects how conversions between mass and moles are done, because now molecular weight is no longer exactly equal numerically (modulo units) to molar weight, though the difference is very slight (about the 7th significant digit).  However, I don’t think that affects any part of the text in the specification, as far as I can tell.