ISO-9006-1994.pdf
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1、INTERNATIONAL STANDARD IS0 9006 First edition 1994-l O-l 5 Uranium metal and uranium dioxide powder and pellets - Determination of nitrogen content - Method using ammonia-sensing electrode Uranium m further heating de- composes this complex resulting in a clear yellow solution of uranium(W). The aci
2、d solution is made alkaline by the addition of excess potassium carbonate solution, the low free acid after dissolution ensuring that the evolution of carbon dioxide is minimal. The excess carbonate converts ammonium ion to ammonia gas and maintains uranium(W) in solution as a complex anion, UO2CO3)
3、3 . 4- The quantity of ammonia present in the alkaline solution is determined by recording the potential indicated by the ammonia-sensing electrode when it is inserted in the solution, adding a known amount of ammonia and again recording the potential indicated by the electrode. The difference betwe
4、en the two values enables the ammonia content of the solution, and hence the nitro- gen content of the sample, to be determined. The ammonia is added in the form of a standard solution of ammonium chloride, the ammonium ion being in- stantly converted to ammonia when it is added to the alkaline solu
5、tion. A blank test is carried out using the amounts of hy- drochloric acid, hydrogen peroxide and water that are used for dissolving the test portion, and following the same procedure for measuring the ammonia content. 3 Reactions u4+ + t00j2- + uo*2+ uog+ + 3CO$- + UO2KO 1 4- 33 NH4+ + OH- + NH3 +
6、HZ0 4 Reagents Use only reagents of recognized analytical grade and distilled water. 4.1 Distilled water. The ammonia concentration shall be less than 0.1 pg/ml; laboratory grade water usually conforms to this requirement. 1 Copyright International Organization for Standardization Provided by IHS un
7、der license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/26/2007 02:25:01 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 9006:1994(E) 0 IS0 This water shall be used to prepare all reagents and shall also be used in the procedure specified
8、in clause 7. Pour off the excess acid and wash thoroughly with water. Drain off the excess water, cover the sample with acetone (4.7) and swirl to mix. Pour off the acetone. 4.2 Hydrochloric acid, p 1,18 g/ml. Dry the cleaned sample with a stream of air and use it as the test sample. 4.3 Hydrogen pe
9、roxide, 290 g/l solution. 4.4 Complexing agent. Commence the procedure (see clause 7) immediately. Dissolve 250 g of anhydrous potassium carbonate and 2,5 g of ethylenediaminetetraacetic acid (EDTA), disodium salt, in water and dilute to 1 I. 6.1.2 Uranium dioxide pellets Crush the sample in a percu
10、ssion mortar and pass it through a 75 urn sieve. Repeat this procedure if necessary until a sieved portion of more than 1 g is available. Retain the sieved portion for use as the test sample. 4.5 Nitrogen, 1 g/l standard solution Weigh approximately 5 g of ammonium chloride and dry it at 120 “C for
11、4 h. Dissolve 3,821 g of the dried material in water and dilute to 1 I. 6.1.3 Uranium dioxide powder 4.6 Nitric acid, p I,42 g/ml. Powder samples shall be analysed without any further preparation. 4.7 Acetone. 5 Apparatus 7 Procedure Usual laboratory apparatus, and 7.1 Preparation of test solution 5
12、.1 Millivoltmeter, with digital readout, capable of discriminating to 0,l mV. 7.1.1 Weigh, to the nearest 0,001 g, 0,56 g to 0,58 g of the uranium dioxide test sample (see 6.1.2 or 6.1.3) or 0.48 g to 0.52 g of the uranium metal test sample (see 6.1.1) and record this mass as m,-,. Transfer the samp
13、le to a 25 ml beaker. 5.2 Ammonia-sensing electrode. When not in use, the electrode shall be stored in a solution consisting of 10 ml of water, 2 ml of com- plexing agent (4.4) and 50 ul of nitrogen standard solution (4.5). NOTE 1 Turnings of uranium metal are easily broken to give the sample mass.
14、Solid pieces are dissolved in nitric acid and a suitable aliquot of the solution taken. 5.3 Magnetic stirrer and plastic-coated stirrer bars. 7.1.2 Add, by pipette, 1 ml of water (4.11, 1 ml of hydrochloric acid (4.2) and 0,5 ml of hydrogen peroxide solution (4.3). Swirl to mix and cover with a watc
15、h-glass. Boil gently until a clear yellow solution is obtained. Allow the solution to cool to ambient tem- perature. 5.4 Micrometer syringe pipette, 500 pl capacity, capable of delivering increments of 0,2 ul. 6 Sampling 6.1 Preparation of the test sample NOTE 2 This dissolution is suitable for all
16、nitrides of uranium. 6.1.1 Uranium metal 7.1.3 Dilute to 15 ml with complexing agent (4.4) and swirl to mix. Add a stirrer bar (5.3) to the solution and cover the beaker with a watch-glass. Place about 2 g of the sample in a 100 ml beaker. Add 10 ml of water (4.1) followed by 10 ml of nitric acid (4
17、.6) and swirl to mix. 7.1.4 Ammonia is lost slowly from the solution and measurements shall be made within 30 min of making the solution alkaline. Stand until all trace of tarnish has been removed and the sample is silver in appearance. 2 Copyright International Organization for Standardization Prov
18、ided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/26/2007 02:25:01 MDTNo reproduction or networking permitted without license from IHS -,-,- 0 IS0 IS0 9006: 1994(E) 7.2 Standard addition procedure where 7.21 Remove the ammonia-sensing electrode (5.2
19、) from the solution in which it is stored and rinse it with water. 7.2.2 Immerse the electrode in the sample solution, prepared in accordance with 7.1, stir and take the voltage reading when it is stable, in millivolts, to the nearest 0,l mV, and record U,. NOTE 3 Stirring by magnetic stirrer should
20、 be carried out continuously and at a steady rate throughout the series of measurements. The stability of the reading will be influenced by the impedance of the millivoltmeter used. A criterion of 0.2 mV/min or less may be appropriate when a high grade meter is used. 7.2.3 Using the micrometer syrin
21、ge (5.41, make an addition of nitrogen standard solution (4.5) until the change in the voltage reading is in the range between 17 mV and 33 mV. Record the volume, in microlitres, of nitrogen standard solution (4.5) added as V. NOTE 4 A volume of V f.rl of nitrogen standard solution contains V pg of
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