Manganese dioxide causes spurious gold values in flame atomic-absorption readings from HBr-Br2 digestions

False readings, apparently caused by the presence of high concentrations of manganese dioxide, have been observed in our current flame atomic-absorption procedure for the determination of gold. After a hydrobromic acid (HBr)-bromine (Br₂) leach, simply heating the sample to boiling to remove excess Br₂ prior to extraction with methyl-isobutyl-ketone (MIBK) eliminates these false readings.