ISO 3119:1976

Boric acid, boric oxide and disodium tetraborates for industrial use — Determination of chromium content — Diphenylcarbazide photometric method

Alkaline fusion of a test portion by sodium carbonate and subsequent neutralization by sulphuric acid. Measurement of the absorption of the complex formed by chromium and diphenylcarbazide at a wavelength of abour 540 nm after adding sodium azide for elimination of the colour caused by manganese.