1、 Reference number ISO/TR 4277:2009(E) ISO 2009TECHNICAL REPORT ISO/TR 4277 First edition 2009-11-01 Cryolite, natural and artificial Conventional test for evaluation of free fluorides content Cryolithe, naturelle et artificielle Essai conventionnel pour lvaluation de la teneur en fluorures libres IS
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7、ights reserved iiiForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a sub
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11、as an International Standard (“state of the art”, for example), it may decide by a simple majority vote of its participating members to publish a Technical Report. A Technical Report is entirely informative in nature and does not have to be reviewed until the data it provides are considered to be no
12、 longer valid or useful. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TR 4277 was prepared by Technical Committee ISO/TC 226, Materials for th
13、e production of primary aluminium. This first edition cancels and replaces ISO 4277:1977, of which it constitutes a minor revision. ISO/TR 4277:2009(E) iv ISO 2009 All rights reservedIntroduction This Technical Report was published in order to retain the method specified in ISO 4277:1977 in a public
14、ly available standard. ISO 4277:1977 was withdrawn in 2004. TECHNICAL REPORT ISO/TR 4277:2009(E) ISO 2009 All rights reserved 1Cryolite, natural and artificial Conventional test for evaluation of free fluorides content 1 Scope This Technical Report describes a conventional test for the evaluation of
15、 the free fluorides content of natural, artificial and recovered cryolite. This method is applicable to products having free fluorides content greater than 0,15 % (mass fraction) of AIF 3or 0,4 % (mass fraction) of NaF. 2 Principle A test portion is sintered with a known quantity of sodium fluoride
16、at 790 20 C for 20 minutes. Under these conditions, aluminium fluoride in excess of that required for the stoichiometric formula AlF 3 3NaF reacts with some of the sodium fluoride to form cryolite. The ground sintered mass is extracted with boiling water and the solution is acidified with hydrochlor
17、ic acid solution to a pH less than 3,7, followed by titration of the excess sodium fluoride with standard volumetric thorium nitrate solution in the presence of alizarin-S as indicator. 3 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or water
18、 of equivalent purity. 3.1 Sodium fluoride, anhydrous, dried at about 120 C to constant mass in a platinum crucible and cooled in a desiccator. 3.2 Gelatine, 3 % freshly prepared solution. 3.3 Hydrochloric acid, approximately 0,1 N solution. 3.4 Sodium fluoride, 4,20 g/l standard solution (correspon
19、ding to 0,1 N). Weigh, to the nearest 0,001 g, 4,20 g of the sodium fluoride (3.1). Transfer quantitatively to a 1 000 ml one- mark volumetric flask containing a little water and, after dissolution, dilute to the mark and mix. Transfer the solution to a suitable plastics bottle. 1 ml of this solutio
20、n contains 4,20 mg of NaF. 3.5 Thorium nitrate, 0,1 N standard volumetric solution. Weigh, to the nearest 0,001 g, 13,805 g of thorium nitrate tetrahydrate Th(NO 3 ) 4 4H 2 O, transfer quantitatively to a 1 000 ml one-mark volumetric flask, dissolve in water, dilute to the mark and mix. ISO/TR 4277:
21、2009(E) 2 ISO 2009 All rights reserved3.6 Buffer solution, pH 2,7. Neutralize a 9,5 % (mass fraction) solution of monochloroacetic acid (CH 2 CI-COOH) with an approximately 10 N sodium hydroxide solution, in the presence of phenolphthalein. Add 50 ml of this solution to 50 ml of the same monochloroa
22、cetic acid solution and mix. 3.7 Alizarin-S (sodium alizarinsulfonate), 0,5 g/l solution. 4 Apparatus Ordinary laboratory apparatus and in particular the following. 4.1 Platinum crucible, diameter approximately 40 mm, height approximately 30 mm. 4.2 Electric furnace, capable of being controlled at 7
23、90 20 C. 5 Procedure 5.1 Test portion Weigh, to the nearest 0,001 g, 4 g of the dried sample (see ISO 1619:1976, 3.3). 5.2 Preparation of the calibration graph 5.2.1 Preparation of the standard matching solutions Into a series of seven 100 ml conical plastics flasks, place the volumes of the standar
24、d sodium fluoride solution (3.4) shown in the following table. Table 1 Volumes of standard sodium fluoride solution Standard sodium fluoride solution (3.4) Corresponding mass of NaF ml mg 0 0 1,0 4,20 3,0 12,60 5,0 21,00 7,0 29,40 9,0 37,80 10,0 42,00 5.2.2 Titration Add to each conical flask 40 ml
25、of water, 5 ml of the buffer solution (3.6), 1 ml of the alizarin-S solution (3.7) and 10 ml of the gelatine solution (3.2). Titrate with the standard volumetric thorium nitrate solution (3.5) until the colour of the indicator changes to pink. ISO/TR 4277:2009(E) ISO 2009 All rights reserved 35.2.3
26、Plotting of the calibration graph Plot a graph having, for example, the masses, in milligrams, of sodium fluoride contained in the standard matching solutions (5.2.1) as abscissa and the volumes, in millilitres, of the standard volumetric thorium nitrate solution (3.5) used for the titrations as ord
27、inates. In the range of concentrations of sodium fluoride considered, the calibration graph is a straight line, whose ordinate at the origin corresponds approximately to 0,1 ml of the standard volumetric thorium nitrate solution. 5.3 Determination 5.3.1 Preparation of the test solution Weigh, to the
28、 nearest 0,001 g, in the platinum crucible (4.1), 0,800 g of the sodium fluoride (3.1). Add the test portion (5.1) and mix carefully with a small platinum spatula. Place the crucible in the electric furnace (4.2), controlled at 790 20 C, and maintain at this temperature for 20 min. Remove the crucib
29、le from the furnace and allow to cool. Transfer the cooled sintered mass to a small, lipped mortar and grind in the presence of a few millilitres of water. Transfer quantitatively to a beaker of suitable capacity, rinse the crucible and the mortar with a few millilitres of water and add the washings
30、 to the beaker. Make up to about 100 ml with water and boil for 1 min. Allow to cool, transfer quantitatively to a 200 ml one-mark volumetric flask, dilute to the mark with water, mix and allow to settle until the supernatant liquid is clear. 5.3.2 Titration Take 10,0 ml of the clear test solution (
31、5.3.1), place in a 100 ml conical flask and dilute to approximately 40 ml. Add 1 ml of the alizarin-S solution (3.7) and add, from a burette, the hydrochloric acid solution (3.3) until the colour of the indicator changes to yellow. Finally, add 5 ml of the buffer solution (3.6) and 10 ml of the gela
32、tine solution (3.2). Titrate with the standard volumetric thorium nitrate solution (3.5) until the colour of the indicator changes to a pink identical to that obtained in the calibration (5.2.2). Read from the calibration graph (5.2.3) the corresponding mass, m 1 , of sodium fluoride. 6 Expression o
33、f results The total mass, m 2 , in grams, of NaF present in the test solution (5.3.1) is given by the equation 21 1 200 1000 10 mm = where m 1is the mass, in milligrams, of NaF found in 10 ml of the test solution (5.3.1) by means of the procedure described in 5.3.2. If m 2is greater than 0,800 g, th
34、e sample contains free NaF, the content of which, expressed as a percentage by mass, is given by the formula 2 0 ( 0,800) 100 m m where m 0is the mass, in grams, of the test portion (5.1). ISO/TR 4277:2009(E) 4 ISO 2009 All rights reservedIf m 2is less than 0,800 g, the sample contains free AIF 3 ,
35、the content of which, expressed as a percentage by mass, is given by the formula 2 0 (0,800 ) 100 1,5 m m where m 0is the mass, in grams, of the test portion (5.1); 1,5 is the ratio of three times the relative molar mass of NaF to the relative molar mass of AIF 3i.e. (3 42)/84 which is the relative
36、molar mass in cryolite. 7 Assessment of results and modified procedure to accommodate special samples 7.1 lt is essential that m 2be greater than 0,15 g for the reaction to go to completion. If m 2is less than or equal to 0,15 g, repeat the analysis, using a smaller test portion or increasing the am
37、ount of the sodium fluoride (3.1) added. 7.2 If the mass m of sodium fluoride to be titrated in 5.3.2 exceeds that which can be accurately read from the calibration graph, carry out the titration with the volume of the test solution (5.3.1) reduced from 10,0 ml to 5,0 ml. Under these conditions, m 2
38、is given by the equation 21 1 200 1000 5 mm = 8 Test report The test report shall include at least the following information: a) a reference to this Technical Report; b) the date on which the sample was taken; c) the date of the determinations and calculations; d) details necessary for the complete
39、identification of the material tested; e) the results and the method of expression used; f) any unusual features noted during the determination; g) any operation not included in this Technical Report or in ISO 1619:1976 to which reference is made, or regarded as optional. ISO/TR 4277:2009(E) ISO 200
40、9 All rights reserved 5Bibliography NOTE ISO 4277:1977 contained a Bibliography similar to the following that was relevant in 1977; most of the methods are now out of date and of little use, except for ISO 1619 and ISO 5938. 1 ISO 1619:1976, Cryolite, natural and artificial Preparation and storage o
41、f test samples 2 ISO 1620:1976, Cryolite, natural and artificial Determination of silica content Reduced molybdosilicate spectrophotometric method 3 ISO 1693:1976, Cryolite, natural and artificial Determination of fluorine content Modified Willard- Winter method 4 ISO 1694:1976, Cryolite, natural an
42、d artificial Determination of iron content 1,10-Phenanthroline photometric method 5 ISO 2366:1974, Cryolite, natural and artificial Determination of sodium content Flame emission and atomic absorption spectrophotometric methods 6 ISO 2367:1972, Cryolite (natural and artificial) Determination of alum
43、inium content 8-Hydroxyquinoline gravimetric method 7 ISO 2830:1973, Cryolite, natural and artificial Determination of aluminium content Atomic absorption method 8 ISO 3391:1976, Cryolite, natural and artificial Determination of calcium content Flame atomic absorption method 9 ISO 3392:1976, Cryolit
44、e, natural and artificial, and aluminium fluoride for industrial use Determination of water content Electrometric method (withdrawn) 10 ISO 3393:1976, Cryolite, natural and artificial, and aluminium fluoride for industrial use Determination of moisture content Gravimetric method 11 ISO 3429:1976, So
45、dium fluoride primarily used for the production of aluminium Determination of iron content 1,10-Phenanthroline photometric method 12 ISO 3430:1976, Sodium fluoride primarily used for the production of aluminium Determination of silica content Reduced molybdosilicate spectrophotometric method 13 ISO
46、3431:1976, Sodium fluoride primarily used for the production of aluminium Determination of soluble sulphates content Turbidimetric method 14 ISO 3566:1976, Sodium fluoride primarily used for the production of aluminium Determination of chlorides content Turbidimetric method 15 ISO 3699:1976, Anhydro
47、us hydrogen fluoride for industrial use Determination of water content Karl Fischer method 16 ISO 4277:1977, Cryolite, natural and artificial Conventional test for evaluation of free fluorides content (withdrawn) 17 ISO 4280:1977, Cryolite, natural and artificial, and aluminium fluoride for industri
48、al use Determination of sulphate content Barium sulphate gravimetric method 18 ISO 5930:1979, Cryolite, natural and artificial, and aluminium fluoride for industrial use Determination of phosphorus content Reduced molybdophosphate photometric method ISO/TR 4277:2009(E) 6 ISO 2009 All rights reserved
49、19 ISO 5938:1979, Cryolite, natural and artificial, and aluminium fluoride for industrial use Determination of sulphur content X-ray fluorescence spectrometric method 20 ISO 6374:1981, Cryolite, natural and artificial, and aluminium fluoride for industrial use Determination of phosphorus content Atomic absorption spectrometric method after extraction ISO/TR 4277:2009(E) ICS 71.060.50 Price based
