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1、INTERNATIONAL STANDARD 4159 INTERNATIONAL ORGANIZATION FOR STANDARDIZATlON*MEWlYtlAPO,WAR OPrAHHBALU4R fl0 CTAHL1APTH3Al heat without exceeding, even locally, the temperature of 60 OC, until the salt is completely dissolved. Cool. Prepare this solution at the time of use. 4.7 Potassium permanganate,
2、 recrystallized. Place 50 g of pure analytical grade potassium permanganate in the conical flask (5.1), and dissolve it in 200 ml of warm distilled water (70 to 80 “C). Fit the reflux condenser (5.2) to the flask and boil the solution for 20 min. Filter the warm solution quickly under vacuum through
3、 a sintered glass funnel (5.3). Cool the filtrate in iced water, stirring vigorously, and allow the fine, crystalline precipitate to settle for IO min. Decant the solution; then, using a glass spatula, transfer the crystalline mass into a funnel with a filter plate, porosity 4, and place under sucti
4、on for a few minutes to remove most of the mother liquor. Dissolve the crystalline mass in 160 ml of distilled water (deionized water is not permitted for this phase), and repeat the recrystallization. After filtering and placing under suction for approximately 5 min, transfer the crystalline mass o
5、nto a 150 mm dia- meter watch glass using a glass spatula, and dry it in air, protected from light and dust. When the crystalline mass no longer agglomerates when crushed with the spatula, dry it at 1 IO “C for 2 h, then transfer it to a weighing bottle fitted with a ground glass stopper. Store in t
6、he dark. This salt contains 34.76 % (m/m) of Mn. 2) Attention is drawn to the hazards associated with perchloric acid when heated to fuming. 1 Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale
7、, 04/28/2007 07:50:51 MDTNo reproduction or networking permitted without license from IHS -,-,- ISO4159-1978 (E) 4.8 Potassium permanganate, about 0.1 N standard volumetric solution. 4.8.1 Preparation Dissolve 3,20 g of potassium permanganate in 1 000 ml of water. Allow to stand for 6 days. Filter t
8、hrough glass wool or a sintered glass filter, then transfer to a brown glass bottle. Mix. 4.8.2 Standardization Place about 2,5 g of the recrystallized potassium per- manganate (4.7), weighed to the nearest 0,0002 g, in a 250 ml conical flask, and follow exactly the procedure specified in 7.3. It is
9、 recommended that this standardization be carried out in parallel with the determination. The manganese equivalent Tof the potassium permanganate solution (4.8), expressed in grams of manganese corre- sponding to 1 ml of solution, is given by the formula T= m, x 34,76 50 100 (V, - vo, x25o 0,069 52
10、m, = v,-v, where ml is the mass, in grams, of the crystallized potassium permanganate (4.7) used; V, is the volume, in millilitres, of the potassium per- manganate solution (4.8) used for the blank test; VI is the volume, in millilitres, of the potassium per- manganate solution (4.8) used for the st
11、andardization. 5 APPARATUS Usual laboratory equipment, and in particular : 5.1 Erlenmeyer conical flask with ground neck. 5.2 Reflux condenser with ground glass joint, to fit the flask (5.1). 5.3 Filter crucibles (porosity 4) or filter funnels, ca- pacity 40 ml. 5.4 Volumetric flask, capacity 250 ml
12、. 5.5 Beaker, capacity 600 ml. 5.6 Conical flask, capacity 250 ml. 5.7 Dish, capacity 250 ml, or beaker, capacity 400 ml, of polytetrafluoroethylene. 5.8 Magnetic stirrer. 5.9 pH meter, fitted with glass and calomel electrodes. 5.10 Potentiometer, fitted with platinum and calomel electrodes. 6 SAMPL
13、E Use powder which will pass through a sieve with a mesh size of 160 urn, prepared in accordance with IS0 3713. 7 PROCEDURE 7.1 Test portion Take a test portion of 1 f 0,000 2 g. 7.2 Blank test Carry out a blank test in parallel with the determination, following the same procedure and using the same
14、 reagents. 7.3 Determination 7.3.1 Attack the test portion as specified in 7.3.1.1 or 7.3.1.2, as appropriate. 7.3.1.1 Ferromanganese Transfer the test portion (7.1) to the conical flask (5.6) and attack it with 20 ml of the hydrochloric acid (4.3) and 0,2 ml of the hydrofluoric acid (4.2), then add
15、 10 ml of the perchloric acid (4.1 ).I) Proceed as specified in 7.3.2. I) Oxidize the solution with nitric acid prior to adding the perchloric acid. 2 , 7.3.1.2 Ferrosilicomanganese Transfer the test portion (7.1) to a dish. or beaker (5.7). Attack it with 10 ml of the hydrochloric acid (4.3), add 1
16、0 ml of the perchloric acid (4.1) then, slowly, about 20 ml of the hydrofluoric acid (4.2). ) Proceed as specified in 7.3.2. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/28/2007 07:50
17、:51 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 4159-1978(E) 7.3.2 Heat gently at first, then progressively increase the heat until the formation of heavy perchloric fumes. Continue heating until a syrupy consistency is obtained and manganese dioxide begins to preci
18、pitate. Allow to cool. 7.3.3 Take up with 20 ml of the hydrochloric acid solution (4.5). Heat gently until the solution clears. Rinse the sides of the vessel carefully with a jet from a wash- bottle and continue heating for a few minutes. Add 100 ml of hot water, and cool to room temperature. Transf
19、er, without filtering, to the volumetric flask (5.4). Rinse the vessel used for the attack carefully, cool and make up to the mark. Shake to mix the solution. 7.3.4 By means of a pipette, transfer 50 ml of the solution to the beaker (5.5). Dilute to 100 ml with water. Add 250 ml of the sodium pyroph
20、osphate solution (4.6). Place the beaker on the magnetic stirrer (5.8) and add a magnet- ized bar. 7.3.5 Adjust the pH of the solution to a value between 6,5 and 7, using the pH meter (5.9), by adding the hydro- chloric acid solution (4.4). NOTE - in the case of ferromanganese containing chromium, i
21、t is necessary to wait for 30 min after the adjustment of the pH of the solution before carrying out the titration. Titrate with the potassium permanganate solution (4.8), adding it slowly to the beaker. Follow the indications of the potentiometer : the end of the titration is obtained when a sudden
22、 increase in potential of at least 100 mV is observed. It is recommended that a second titration be carried out under the same conditions on another aliquot portion of the test solution. 8 EXPRESSION OF RESULTS The manganese content, expressed as a percentage by mass of the sample, is given by the f
23、ormula 250 100 T(V,- V,) x-x- 50 m. = 500 T(V, - Vo) mo where m. is the mass, in grams, of the test portion (7.1); VO is the volume, in millilitres, of the potassium per- manganate solution (4.8) used for the blank test; V, is the volume, in millilitres, of the potassium permanganate solution (4.8)
24、used for the deter- mination (7.3.5); T is the manganese equivalent of the potassium per- manganate solution (4.8). expressed in grams of manganese corresponding to 1 ml of the solution. 9 REPRODUCIBILITY Experience has shown that the 95 % confidence limits for an experienced operator are f 0,20 %.
25、10 TEST REPORT The test report shall include the following particulars : a) the reference of the method used; b) the results and the method of expression used; c) any unusual features noted during the determination; d) any operation not included in this International Standard or regarded as optional. 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 07:50:51 MDTNo reproduction or networking permitted without license from IHS -,-,-