[SeeSac]

I assume your table gives 35.453 since that is what you have been quoting.

Now (from wikipedia):

“Chlorine has a wide range of isotopes. The two stable isotopes are 35Cl (75.77%) and 37Cl (24.23%). Together they give chlorine an atomic weight of 35.4527 g/mol.”

thus if your ‘old’ table gives 35.453 it is giving the ELEMENTAL mass which is based on the ratio of isotopes.

[BenKenobi]

Wikipedia is God.