ISO 2214:1972

The principle consists in removal of the boron by evaporation with methanol and separation of manganese and other metals from the residue, by extraction with chloroform, as their diethyldithiocarbamates. Wet destruction of the diethyldithiocarbamates with a sulphuric acid/ hydrogen peroxide mixture. Removal of any interfering iron by extraction as the thiocyanate. Formation of the coloured manganese formaldoxime complex in alkaline solution and photometric measurement at a wavelength of approximately 450 nm.