ISO 2072:1981

The 1-(2-pyridilazo)-2-naphthol method is applicable to products having zinc contents in the range between 0,002 % (m/m) and 0,12 % (m/m). Alkaline fusion of a test portion, and dissolution of the fused mass in nitric acid. Separation of the zinc in the form of its thiocyanate by extraction with 4-methylpentan-2-one. Re-extraction of the zinc with an aqueous hydrochloric acid solution. Formation of the PAN-zinc complex, at pH 7,5, in the presence of tartaric acid, sodium thiosulphate and 1-nitrose-2-naphthol-3,6-du