4140 OSI) International Standard INTERNATIONAL ORGANIZATION FOR STANDARDIZATION MEXAYHAPOAHAR OPTAHM3ALMA IO CTAHAAPTM3AWM+ORGANISATION INTE RNATIONALE DE NORMALISATION Ferrochromium and ferrosilicochromium -- Determination of chromium content - Potentiometric method Ferro-chrome et ferro-silico-chrome --- Dosage du chrome - Methode potentiometrique First edition -- 1979-09-15 UDC 669.15-198 : 543.257.1 : 546.76 ISO 4140-1979 (E) Ref.No.ISO 4140-1979 (E) Descriptors: ferroalloys, silicon containing alloys, ferrochromium, chromium containing alloys, ferrosilicochromium, chemical analysis, determination of content, chromium, potentiometric analysis Price based on 3 pages Foreword Iso (the International Organization for Standardization) is a worldwide federation of national standards institutes (IsO member bodies). The work of developing Interna- tional Standards is carried out through IsO technical committees. Every member body interested in a subject.for which a technical committee has been set up has the right to be represented on that committee. International organizations, governmental and non- governmental, in liaison with iso, also take part in the work. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the ISo Council. International Standard ISO 4140 was developed by Technical Committee ISO/TC 132, Ferroalloys, and was circulated to the member bodies in January 1978. It has been approved by the member bodies of the following countries : India South Africa, Rep. of Australia Austria Iran Spain Bulgaria Italy Sweden Canada Japan Turkey United Kingdom Czechoslovakia Mexico Norway USA Egypt, Arab Rep. of USSR France Poland Yugoslavia Germany, F. R. Romania No member body expressed disapproval of the document. International Organization for Standardization, 1979 ? Printed in Switzerland INTERNATIONAL STANDARD ISO 4140-1979 (E) Ferrochromium and ferrosilicochromium - Determination of chromium content --- Potentiometric method Scope and field of application 4.2 Sodium carbonate. 1 This International Standard specifies a potentiometric method 4.3 Ammonium persulphate [(NH4’2S20g] for the determination of the chromium content of fer- rochromium and ferrosilicochromium. 4.4 Urea. The method is applicable to all grades of these ferroalloys. 4.5 Phosphoric acid, @ 1,7 g/ml. 2 Reference 4.6 Nitric acid, 1,42 g/ml. Iso 3713, Ferroalloys -- Sampling and preparation of samples General rules. 1) 4.7 Hydrofluoric acid, @ 1,14 g/mi. 4.8 Sulphuric acid, 50 % (V/V) solution. 3Principle To 400 ml of water, add cautiously 500 ml of sulphuric acid Fusion of a test portion with sodium peroxide, dissolution of (o 1,84 g/ml), mix, cool, dilute to 1 000 ml and mix. the melt in water, and acidification of the aqueous solution with sulphuric acid; alternatively, for some ferroalloys, dissolution of 4.9 Hydrochloric acid, 40 % (V/V) solution. a test portion by direct acid attack. Oxidation of chromium with ammonium persulphate in the presence of silver ions as To 600 ml of water, add 400 ml of hydrochloric acid catalyst. Determination of the sum of chromium and vanadium (o 1,19 g/ml), and mix. bypotentiometric titrationwith ammonium iron(ll)sulphate Reoxidation of vanadium with potassium permanganate; destruction of the excess of permanganate by nitrite, and 4.10 Silvernitrate solution. destruction of the excess of nitrite by urea. Determination of vanadium by potentiometric titration with ammonium iron(ll) Dissolve 5 g of silver nitrate in water and dilute to 1 000iml. sulphate, and determination of the chromium content by dif- ference. 4.11 Potassium permanganate solution. The reactions are the following : Dissolve 2,5 g of potassium permanganate in water and dilute to 100 ml. Cr203- + 6 Fe2+ + 14H+ -→ 2 Cr3+ + 6 Fe3+ + 7H20 4.12 Potassium nitrite solution. VO± + Fe2+ + 2H+ → VO2+ + Fe3+ + H20 Dissolve 1 g of potassium nitrite in wa