7693 International Standard (ISO INTERNATIONAL ORGANIZATION FOR STANDARDIZATION-MEKAYHAPOAHAR OPrAHM3ALMA NO CTAHAAPTW3ALWW-ORGANISATION INTERNATIONALEDE NORMALISATION Ferrotungsten -- Determination of tungsten content - Cinchonine gravimetric method Ferro-tungstene-Dosage du tungstene-Methode gravimetrique a la cinchonine Firstedition-1984-03-01 ISO 7693-1984 (E) UDC669.15*27-198:543.21: 546.78 Ref.No.ISO7693-1984 (E) Descriptors : ferroalloys, ferrotungsten, chemical analysis, determination of content, tungsten, gravimetric analysis Pricebasedon4page Foreword ISO(theInternationalOrganizationforStandardization)isaworldwidefederationof national standards bodies (Iso member bodies). The work of developing International Standards is carried out through Iso technical committees. Every member body interested in a subject for which a technical committee has been authorized 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 bythe technical committees are circulated to the member bodies for approval before their acceptance as International Standards by theISo Council. International Standard ISO7693 was developed byTechnical Committee ISO/TC 132, Ferroalloys, and was circulated to the member bodies in April 1982. It has been approved by the member bodies of the following countries: Austria Iran Romania Italy South Africa, Rep. of Canada Japan Spain China Korea, Rep. of Sweden Czechoslovakia Mexico UnitedKingdom Egypt, Arab Rep. of Norway USA Poland USSR Thememberbodiesofthefollowingcountriesexpresseddisapprovalofthedocument ontechnical grounds: Australia France INTERNATIONALSTANDARD ISO 7693-1984 (E) Ferrotungsten - Determination of tungsten content Cinchonine gravimetric method Scope and field of application 4.1 Sodium carbonate. This International Standard specifies a cinchonine gravimetric method for the determination of the tungsten content of ferro- 4.2 Acetone. tungsten.It also specifies,in the annex,a spectrometric method for the determination of molybdenum which interferes 4.3 Diammonium hydrogen citrate [(NH4)2HCsHgO7]. with the determination. 4.4 Diboron trioxide (B203). The method is applicable to ferrotungsten having tungsten contentsbetween70and 90% (m/m). 4.5 Nitric acid, @ 1,40 g/ml, approximately 14 mol/l solution. 2 Reference 4.6 Hydrofluoric acid, @ 1,16 g/ml, approximately 48 % Iso3713,Ferroalloys-Samplingandpreparationofsamples (m/m)solution -Generalrules.1) 4.7 Hydrochloric acid, g 1,19 g/ml, approximately 12 mol/l 3.Principle solution. Dissolution of a test portion using hydrofluoric, nitric and 4.8Ethanol, Q approximately 0,790 g/ml. sulphuric acids. Evaporation of the solution until copious white fumes are evolved. 4.9 Sulphuric acid, diluted 1 + 1. Separation and fusion of the residue with sodium carbonate and diboron trioxide. Dissolution of the fused residue in hot Carefullyadd1volumeofsulphuricacid(g1,84g/ml,approxi- water. mately18mol/lsolution)to1volumeofwaterandmix thoroughly whilst cooling. Precipitation of the tungsten with cinchonine and α-benzoin oxime, ignition of the precipitate and weighing of the impure tungstic oxide. Purification of the impure tungstic oxide by 4.10 Hydrochloric acid, diluted 1+9. fusion with sodium carbonate, dissolution in hot water, fil- tration and recovery of the insoluble impurities Add 1 volume of the hydrochloric acid (4.7) to 9 volumes of water and mix thoroughly. Spectrometric determination of molybdenum (see the annex). 4.11 Hydrochloric acid, diluted 1 + 99. Determination of the tungsten content from the difference be- tween the mass of the impure tungstic oxide and that of the Add 1 volume of the hydrochloric acid (4.7) to 99 volumes of impurities. water and mix thoroughly. Reagents 4.12 Ammonium hydroxide, diluted 1 + 1. During the anaiysis, unless otherwise stated, use only reagents Add 1 volume of ammonium hydroxi