Absolute isotopic abundance ratios and the atomic weight of a reference sample of potassium

So lid s amp le . th e rma l ioni za tion. ma ss s pec trom e try ha s bee n used to obtai n a bs o lut e va lu es ror t he iso top ic ab und a nce ra t ios of a refe re nce sa m pie or potass iu m. S La nd a rd s of known is ot o pi e c o mp os i Lio n , pre pare d b y gr av im e tri c all y mixin g nea rl y iSo Lopi ca ll y and c he mi c a ll y pure se parat e d isotopes of "" K a nd " K. we re use d for c a libra t ion . Th e a b solute iso top ic a bund a nce ra t ios a re "" K/ 41 " = 13.8566 0.0063 a nd ""K /41 K = 0.001 7343 0.0000061 whi c h yie ld a to m pe rce nt co mpos iti on s of "!o K = 93.258 1 0.0029 . . w " = 0.01 J 67 0.00004. a nd ." K = 6.