5975 International Standard (TSO Chromium ores - Determination of calcium and magnesium contents -- EDTA titrimetric method Minerais de chrome -- Dosage du calcium et du magnésium -- Méthode titrimetrique a I'EDTA First edition - 1983-07-01 UDC 553.461 : 543.24 : 546.41 : 546.46 Ref. No. ISO 5975-1983 (E) 5975-1983 (E) Descriptors : chromate minerals, chemical analysis, determination of content, calcium, magnesium, volumetric analysis. SO yright International Organization for Standardization Price based on 4 pages Not for Resale Foreword 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 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 5975 was developed by Technical Committee ISO/TC 65, Manganese and chromium ores, and was circulated to the member bodies in April 1982. It has been approved by the member bodies of the following countries: Austria Spain India Thailand Brazil Italy Japan United Kingdom China Poland USSR Czechoslovakia Egypt, Arab Rep. of Romania South Africa, Rep. of France The member body of the following country expressed disapproval of the document on technical grounds: Australia @ International Organization for Standardization, 1983 Printed in Switzerland working permitted without license from IHS Not for Resale ISO 5975-1983 (E) INTERNATIONAL STANDARD Chromium ores - Determination of calcium and magnesium contents - EDTA titrimetric method 1 Scope and field of application 4.3 Nitric acid, g 1,40 g/ml. This International Standard specifies an EDTA titrimetric 4.4 Perchloric acid, g 1,50 g/ml. method for the determination of the calcium and magnesium contents of chromium ores. 4.5 Hydrochloric acid, @ 1,19 g/ml. The method is applicable to products having a calcium content greater than 0,1 % (m/ m) and magnesium content greater than 4.6 . Hydroffuoric acid, g 1,13 g/ml, 40 % (m/m) solution. 3,0 % (m/m). This International Standard should be read in conjunction with 4.7 Ammonia solution, 0,91 g/ml. ISO 6629. 4.8 Ammonia solution, diluted 1 + 100. 2 Reference 4.9 Ethanol, rectified. Iso 6629, Chromium ores and concentrations - Methods of chemical analysis - General instructions. 4.10 Hydrochloric acid, diluted 1 + 3. 3 Principle 4.11 Hydrochloric acid, diluted 1 + 100. Decomposition of the test portion with nitric and perchloric 4.12 Sulfuric acid, diluted 1 + 1. acids. In the case of ores difficult to decompose - -filtration of insol- 4.13 Ammonium persulfate, 20 % (m/m) solution. uble residue, incineration, treatment with hydrofluoric acid, fusion with sodium carbonate and combination of the melt 4.14 Sodium hydroxide, 40 % (m/m) solution. solution with the main solution. Separation of the bulk of chromium as chromyl chloride. Prepare the solution fresh using distilled water, previously Separation of iron, titanium, aluminium and manganese with boiled for 30 min and cooled. ammonia solution in the presence of ammonium persulfate. 4.15 Magnesium sulfate, 0,025 mol/l solution. Determination of calcium in the aliquot portion of the main solution by titration with a standard volumetric EDTA solution Dissolve 3,009 3 g of magnesium sulfate previously dried at (pH ~ 12,5) using fluorexon as an indicator. 220 ± 10 °c till constant mass in water, transfer to a 1 000 ml one-mark volumetric flask, dilute to the mark with water and Determination of calcium and magnesium in the second aliquot mix. portion of the main solution by titration with a standard volumetric EDTA solution (pH ~ 10) using Eriochrome black T as