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1、INTERNATIONAL STANDARD 3909 INTERNATIONAL ORGANIZATION FOR STANDARDlZATlON.METflYHAPOflHAR OPrAHU3AUHII II0 CTAHAPTH3ALWi.ORGANlSATlON INTERNATIONALE DE NORMALISATION Hardmetals - Determination of cobalt - Potentiomkric method Me taux durs - De termination du cobalt - Me thode potentiome trique Firs
2、t edition - 1976-10-15 iii UDC 621.762 : 546.73 : 543.257.1 Ref. No. IS0 3909-1976 (E) K 0) 7 8 Descriptors : powder metallurgy, sintered products, hardmetals, carbides, chemical analysis, determination of content, cobalt, E potentiometric analysis. ; Price based on 3 pages Copyright International O
3、rganization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 07:58:18 MDTNo reproduction or networking permitted without license from IHS -,-,- FOREWORD IS0 (the International Organization for Standardization) is a w
4、orldwide federation of national standards institutes (IS0 Member Bodies). The work of developing International Standards is carried out through IS0 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
5、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 IS0
6、 Council. International Standard IS0 3909 was drawn up by Technical Committee ISOfTC 119, Powder metallurgical materials and products, and was circulated to the Member Bodies in July 1975. It has been approved by the Member Bodies of the following countries : Austria Morocco Czechoslovakia Poland Fr
7、ance Romania Germany South Africa, Rep. of Ireland Spain Italy Sweden Turkey United Kingdom U.S.A. U.S.S.R. The Member Bodies of the following countries expressed disapproval of the document on technical grounds : Australia Canada 0 International Organization for Standardization, 1976 l Printed in S
8、witzerland Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 07:58:18 MDTNo reproduction or networking permitted without license from IHS -,-,- INTERNATIONAL STANDARD _ IS0 3909-19
9、76 (E) Hardmetals - Determination of cobalt - Potentiometric method 1 SCOPE This International Standard specifies a potentiometric method for the determination of the cobalt content of hardmetals. 2 FIELD OF APPLICATION This method is applicable to - carbides and binder metal powder mixtures, free o
10、f lubricant, - all grades of presintered or sintered hardmetals, having a cobalt content exceeding 1 % (m/m). 3 PRINCIPLE Oxidation of cobalt to the trivalent state in a strongly ammoniacal solution with an excess of potassium hexa- cyanoferrate( I I I). Potentiometric back-titration of the excess w
11、ith cobalt sulphate solution. 4 INTERFERING ELEMENTS The effect of interfering elements, for example vanadium and manganese, shall be taken into account. Vanadium and manganese are also oxidized by hexacyanoferrate(lll). Vanadium reacts stoichiometrically and a correction can be applied if the vanad
12、ium content is below 0,5 % (m/m). Manganese reacts almost stoichiometrically up to 0,2 % (m/m) only if the sum of tantalum and niobum in the hardmetal is less than 0,02 % (m/m). Above this level the method is applicable only if the manganese content is less than 0,03 % (m/m). 5 REAGENTS During the a
13、nalysis, use only reagents of recognized analytical grade and only distilled water or water of equiv- alent purity. 5.1 Ammonium sulphate. 5.2 Hydrochloric acid, p 1 ,I9 g/ml. 5.3 Hydrofluoric acid, p 1 ,I 2 g/ml. 5.4 Nitric acid, p I,42 g/ml. 5.5 Sulphuric acid, p I,84 g/ml. 5.6 Ammonia solution, p
14、 0.91 g/ml. 5.7 Ammonium citrate solution. Dissolve 100 g of citric acid in 900 ml of water and add 100 ml of the ammonia solution (5.6). 5.8 Cobalt sulphate, standard reference solution contain- ing 3 g of cobalt per litre. Prepare the solution from compact metallic cobalt, or from diammonium cobal
15、t sulphate, or from cobalt sul- phate. If necessary, establish the titre gravimetrically with I-nitroso-naphthol-2, or electrolytically. 5.9 Potassium hexacyanoferrate(lll), standard volumetric solution. 1 I should correspond to approximately 3 g of cobalt. Dissolve 17 g of KaFe(CN)e in 1 I of water
16、. Determine the relationship between the volumes of the cobalt sulphate solution (5.8) and the potassium hexa- cyanoferrate(lll) solution (5.9) in the following way. 5.9.1 Transfer into a 400 ml beaker 5 g of the ammonium sulphate (5.11, 40 ml of the ammonium citrate solution (5.71, 50 to 100 ml of
17、water, 80 ml of the cooled ammonia solution (5.61, and from a burette approximately 9 ml of the potassium hexacyanoferrate(lll) solution (5.9). Volume used : Va ml. Immediately titrate with the cobalt sulphate solution (5.8). Volume used : V, ml. 5.9.2 Calculate the relationship according to the for
18、mula 5.10 Methyl red indicator, 1 g/l solution, or indicator paper for pH 3 to 5. 1 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 07:58:18 MDTNo reproduction or networking perm
19、itted without license from IHS -,-,- IS0 3909-1976 (E) 6 APPARATUS Ordinary laboratory apparatus and 6.1 Potentiometric titration apparatus with stirrer or some other arrangement for agitating. 6.2 Platinum electrode. 6.3 Tungsten wire or any other reference electrode. 6.4 Burettes, of capacity 10 m
20、l. 7 SAMPLING 7.1 The sample shall be crushed to a powder in a mortar made of a material which does not alter the sample composition. The powder shall pass a 0,18 mm sieve. 7.2 The analysis shall be carried out on two or three test portions. 8 PROCEDURE 8.1 Test portion Weigh, to the nearest 0,000 1
21、 g, 0,l to 05 g of the test sample, depending on the cobalt content. 8.2 Attack Transfer the test portion into a 400 ml beaker, add IO to 15 ml of the sulphuric acid (5.51, 3 ml of the hydrochloric acid (5.2) and 5 g of the ammonium sulphate (5.1). Cover the beaker with a watch-glass and heat until
22、complete dissolution is achieved. Cool. Add, in small portions, 40 to 50 ml of the ammonium citrate solution (5.7). Rinse the watch-glass and the beaker walls with 20 to 50 ml of water. Heat the solution gently until all salts are dissolved. Cool. The following alternative method of attack may be us
23、ed. Transfer the test portion into a 400 ml polypropylene beaker or into a platinum dish, add 10 ml of water and 5 ml of the hydrofluoric acid (5.3) and cover the beaker with a polypropylene cover. Warm to approximately 60 C. Add the nitric acid (5.4), drop by drop, until dissolution is complete. Co
24、ol. Add, in small portions, 10 ml of the sulphuric acid (5.5) and 40 to 50 ml of the ammonium citrate solution (5.7). (If vanadium is present, heat the solution and cool again.) Rinse the cover and the beaker walls with 20 to 50 ml of water. 8.3 Neutralization Add 1 drop of the methyl red indicator
25、solution or use the indicator paper (5.101. Carefully neutralize most of the acid with the ammonia solution (5.6) to a weakly acid solution (pH 3 to 5). Avoid over-neutralizing. Cool. 8.4 Titration Add 80 ml of the ammonia solution (5.6) preferably cooled to 10 “C. Immediately add the potassium hexa
26、cyano- ferrate(lll) solution (5.9) from a burette to an excess of a few millilitres. Volume used : VI ml. Back-titrate with the cobalt sulphate solution (5.8). Volume used : V, ml. 9 EXPRESSION OF RESULTS 9.1 Calculation The cobalt content, expressed as a percentage by mass, is given by the formula
27、(KxV,-V,)xTx100 m where K is as defined in 5.9.2; T is the mass, in grams, of cobalt in 1 ml of the cobalt sulphate solution; m is the mass, in grams, of the test portion. The result shall be rounded to the nearest 0.01 %. 9.2 Corrections As a tentative guide, the following correction values may be
28、used. Vanadium : 0,100 % (m/m) vanadium is equal to 0,116 % (m/m) cobalt. Manganese : 0,100 % (m/m) manganese is equal to 0,107 % (mlm) cobalt. 9.3 Tolerances The deviations between two or three independent deter- minations shall not exceed the values shown in the table. Cobalt content % from 1 to 5
29、 over 5 to a over a to 20 over 20 Range for two Range for three. determinations determinations % % 0,lO 0.12 0,15 0.18 0,20 0.25 0,30 0,35 9.4 Final result Report the arithmetical mean of acceptable determinations rounded to the nearest 0,l %. 2 Copyright International Organization for Standardizati
30、on Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 07:58:18 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 3909-1976 (E) 10 TEST REPORT The test report shall include the following information : a) referen
31、ce to this International Standard; b) all details necessary for identification of the test sample; c) the result obtained; d) all operations not specified by this International Standard, or regarded as optional; e) details of any occurrence which may have affected the result. 3 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 07:58:18 MDTNo reproduction or networking permitted without license from IHS -,-,-