1、BRITISH STANDARD BS 5050:1974 Methods of test for Cryolite UDC 549.461.12:543BS5050:1974 This British Standard, having been approved by the ChemicalsIndustry StandardsCommittee, was published under the authority ofthe Executive Board on 30August1974 BSI 12-1999 The following BSI references relate to
2、 the work on this standard: Committee reference CIC/24 Draft for comment 70/12741 ISBN 0 580 08071 4 Co-operating organizations The Chemicals Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government department
3、s and scientific and industrial organizations: British Steel Industry Chemical Industries Association* Department of Health and Social Security Department of Trade and Industry* Department of Trade and Industry Laboratory of the Government Chemist* Fertilizer Manufacturers Association Limited Minist
4、ry of Agriculture, Fisheries and Food National Sulphuric Acid Association Royal Institute of Public Health and Hygiene Soap and Detergent Industry Association The Government departments and industrial organization marked with an asterisk in the above list, together with the following, were directly
5、represented on the committee entrusted with the preparation of this British Standard: Aluminium Federation British Ceramic Research Association Royal Institute of Chemistry Society for Analytical Chemistry Society of Chemical Industry Amendments issued since publication Amd. No. Date of issue Commen
6、tsBS5050:1974 BSI 12-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Preparation and storage of test samples 1 3 Determination of silica content 1 4 Determination of fluorine content 3 5 Determination of iron content 6 6 Determination of sodium content 8 7
7、Determination of aluminium content (gravimetric method) 10 8 Determination of aluminium content (atomic absorption method) 11 Figure 1 Typical form of steam distillation apparatus for use in determinationof fluorine content 14 Publications referred to Inside back coverBS5050:1974 ii BSI 12-1999 Fore
8、word This British Standard has been prepared under the authority of the Chemicals Industry Standards Committee in order to provide methods for the analysis of natural and artificial cryolite. In the drafting of this standard, account has been taken of methods adopted by the International Organizatio
9、n for Standardization (ISO), in the preparation of which the United Kingdom has been an active participant. It is intended to provide further methods, in the form of addenda to this standard, as the work of Technical Committee 47 Chemistry, and, in particular, ISO/TC47 Sub-committee7 Alumina and rel
10、ated compounds, advances. This standard prescribes methods of test only, and should not be used or quoted as a specification defining limits of purity. Reference to the standard should be in a form of words indicating that the methods of test used conform to BS5050. A British Standard does not purpo
11、rt to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front co
12、ver, pagesi andii, pages1 to14, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS5050:1974 BSI 12-1999 1 1 Scope This British Standard describ
13、es methods of test for natural and artificial cryolite having a NaF : AlF 3ratio of between3 and1.7. NOTEThe titles of the British Standards and ISO publications referred to in this standard are listed on the inside back cover. 2 Preparation and storage of test samples 2.1 Introduction. This clause
14、is based on ISO/R1619, modified to take into account the comments made by the United Kingdom during its development. The method described is intended for the preparation of two test samples from a laboratory sample which shall be representative of the material under test, the two samples being: a) a
15、 crude sample for moisture determination and certain physical tests, and b) a ground and dried analytical sample for other tests. 2.2 Preparation of crude sample. Thoroughly mix3 kg of the laboratory sample and place approximately300g of it in an airtight container of such a capacity that it is near
16、ly filled by the sample. 2.3 Preparation of analytical sample 2.3.1 Principle. The sample is ground, sieved until the whole passes through a0.125mm aperture sieve, well mixed and dried at110 C. 2.3.2 Procedure. Sieve approximately100g of the laboratory sample using a0.125mm aperture sieve, complying
17、 with the requirements of BS410 and constructed of a material that cannot cause introduction of the impurities that are being determined. Select the sieve material in relation to the nature of the impurities to be determined. Grind the material remaining on the sieve in a corundum mortar and sieve a
18、gain. Add the sieved part previously obtained and mix carefully. Repeat the crushing, sieving and mixing operations until none of the material remains on the sieve. Place the sample thus prepared in a platinum dish and dry for2h in an electric oven, ventilated by convection and controlled at110 2 C.
19、 Then allow to cool in a desiccator containing fresh phosphorus pentoxide and keep the dried sample in an airtight container of a capacity such that it is nearly filled by the sample. 3 Determination of silica content 3.1 Introduction. This clause is based on ISO/R1620, modified to take into account
20、 the comments made by the United Kingdom during its development. 3.2 Principle. The sample is fused with a mixture of sodium carbonate and boric acid. The fused mass is dissolved in excess nitric acid so that the pH of the resultant solution is between0.3 and0.5 after dilution to250ml. The silicon i
21、s complexed with sodium molybdate in acid solution and the complex reduced. The absorbance of the reduced silicomolybdate complex is measured at a wavelength of about815nm. The method is applicable provided that the P 2 O 5 1)content does not exceed0.02%. 3.3 Reagents. The reagents used shall be of
22、a recognized analytical reagent quality. Water complying with the requirements of BS3978 shall be used throughout. NOTEWater produced by ion-exchange may not be suitable, because it may have too high a silica content. 3.3.1 Sodium carbonate, anhydrous. 3.3.2 Boric acid 3.3.3 Ascorbic acid, 20 g/l so
23、lution, freshly prepared. 3.3.4 Tartaric acid, 100 g/l solution. 3.3.5 Nitric acid, approximately 8N solution. Dilute 540 ml of nitric acid solution, approximately1.40g/ml, about68% (m/m) solution, with water to1000ml. 3.3.6 Sulphuric acid, approximately 16N solution. Carefully add450ml of sulphuric
24、 acid solution, approximately1.84g/ml, about96% (m/m) solution, to about500ml of water. Cool and dilute to1000ml. 3.3.7 Sodium molybdate, 195 g/l solution. Dissolve 19.5 g of sodium molybdate dihydrate, Na 2 MoO 4 . 2H 2 O, in hot water, cool, dilute with water to100ml and mix. Store in a polyethyle
25、ne bottle. If necessary, filter before use. 3.3.8 Stock silica solution, corresponding to0.5g of SiO 2per litre. 1) The preparation of a method for the determination of phosphorus is being undertaken, and will be included in an addendum to this standard.BS5050:1974 2 BSI 12-1999 Into a platinum cruc
26、ible weigh, to the nearest0.001g,0.500g of finely ground quartz, previously heated at1000 C for1h and cooled in a desiccator. Add5g of the anhydrous sodium carbonate (3.3.1) to the crucible, mix thoroughly and heat until its contents are completely fused. Allow to cool, add hot water to the crucible
27、 and use gentle heat to complete solution of the contents. Transfer to a polyethylene beaker and allow to cool. Transfer to a1000ml one-mark volumetric flask (BS1792), dilute with water to the mark and mix. Transfer without delay to a polyethylene bottle. 3.3.9 Standard silica solution, correspondin
28、g to5mg of SiO 2per litre. Pipette 50.0 ml of the stock silica solution (3.3.8) into a1000ml one-mark volumetric flask (BS1792), dilute with water to the mark and mix. Pipette50.0ml of this solution into a250ml one-mark volumetric flask (BS1792), dilute with water to the mark and mix. This solution
29、shall be freshly prepared. 1 ml of this diluted solution N 5 4g of SiO 2 . 3.4 Apparatus. Ordinary laboratory apparatus and the following are required. 3.4.1 pH meter, with glass and calomel electrode assembly. Essential performance requirements are given in BS2586, BS3145 and BS3422. 3.4.2 Photoele
30、ctric absorptiometer or spectrophotometer, with1cm and4cm cells. 3.4.3 One-mark volumetric flask, 250 ml capacity, complying with the requirements of BS1792. 3.4.4 Eight one-mark volumetric flasks, 100 ml capacity, complying with the requirements of BS1792. 3.4.5 Platinum dish, approximately100mm di
31、ameter and45mm depth, fitted with a platinum lid. 3.5 Procedure 3.5.1 Preparation of calibration graph 3.5.1.1 Preparation of the blank solution. Weigh30g of the sodium carbonate (3.3.1) and10g of the boric acid (3.3.2) into the platinum dish (3.4.5) and mix thoroughly. Cover the dish with its lid,
32、place in an electric furnace, controlled at550 25 C, and allow it to remain at this temperature until the reaction has ended. Transfer the dish to an electric furnace, controlled at750 25 C, making sure that this temperature is maintained for5min. Remove the dish and allow it to cool in air. Add abo
33、ut125ml of boiling water to the dish, heating gently until the material is dissolved. After cooling slightly, transfer the contents of the dish to a polyethylene beaker, of suitable capacity, containing50ml of the nitric acid solution (3.3.5), and carefully wash the dish and lid, first with45ml of t
34、he nitric acid solution and then with water, transferring the washings to the polyethylene beaker. Carefully transfer the contents of the beaker, by washing, to a glass beaker. Simmer gently for several minutes. Cool and transfer to the250ml one-mark volumetric flask (3.4.3) and dilute to the mark.
35、3.5.1.2 Colour development. Transfer20ml of the blank solution (3.5.1.1) into a beaker and add15ml of water,15ml of the standard silica solution (3.3.9) and5ml of the sodium molybdate solution (3.3.7). Mix thoroughly and, using the pH meter (3.4.1), adjust the pH of the solution to between0.85 and0.
36、90 by the addition of the nitric acid solution(3.3.5). This pH value should relate to a solution volume of65ml. Note the volume of nitric acid solution added to adjust the pH value. Discard this solution. Into a series of six of the100ml one-mark volumetric flasks (3.4.4), transfer20ml of the blank
37、solution (3.5.1.1) and the volume of nitric acid solution determined above. Transfer amounts of the standard silica solution (3.3.9) equivalent to 0 4g (reagent blank) to125 4g of silica, increasing by stages of25 4g, and treat each solution in the following manner. Dilute to 60 ml with water and th
38、en add5ml of the sodium molybdate solution (3.3.7). Mix thoroughly and allow to stand for15min to25min at20 C to25 C. Then add5ml of the tartaric acid solution(3.3.4),11ml of the sulphuric acid solution(3.3.6) and finally2ml of the ascorbic acid solution (3.3.3). Mix, dilute to the mark with water a
39、nd mix again. 3.5.1.3 Photometric measurements. After an interval of10min to40min, measure the absorbance of each solution against water at the wavelength of maximum absorption (approximately815nm), using4cm cells, and prepare a calibration graph. NOTEFor samples of higher silica content, where it i
40、s necessary to use1cm cells in the determination, a calibration graph covering the appropriate range should be prepared using1cm cells.BS5050:1974 BSI 12-1999 3 3.5.2 Determination 3.5.2.1 Preparation of the test solution. Weigh 12 g of the sodium carbonate (3.3.1) and4g of the boric acid (3.3.2) in
41、to a platinum dish similar to that used for the preparation of the blank solution (3.5.1.1). Add1.000 0.001g of the analytical sample (see2.3) and mix thoroughly. Cover the dish with its lid, place in an electric furnace, controlled at550 25 C, and allow it to remain at this temperature until the re
42、action subsides (about30min). Transfer the dish to an electric furnace, controlled at750 25 C, making sure that this temperature is maintained for20 min. Remove the dish and allow it to cool in air. Add about50ml of boiling water to the dish, heating gently until the solid is dissolved. After coolin
43、g slightly, transfer the contents of the dish to a polyethylene beaker, of suitable capacity, containing20ml of the nitric acid solution (3.3.5). Dissolve any residue adhering to the walls of the dish with a further18 ml of the nitric acid solution and carefully wash the dish and lid with hot water,
44、 transferring the washings to the polyethylene beaker. Carefully transfer the contents of the beaker, by washing, to a glass beaker. Simmer gently for several minutes. Cool and transfer to the250ml one-mark volumetric flask (3.4.3) and dilute to the mark. Transfer the solution without delay to a pol
45、yethylene bottle. 3.5.2.2 Colour development. Transfer50.0 ml of the test solution (3.5.2.1) into a beaker, add5ml of the sodium molybdate solution (3.3.7) and mix. Using the pH meter, adjust the pH value of the solution to between0.85 and0.90 by the addition of the nitric acid solution (3.3.5). Not
46、e the volume of nitric acid solution added to adjust the pH value. Discard this solution. Transfer 50.0 ml of the test solution (3.5.2.1) to one of the100ml one-mark volumetric flasks (3.4.4). Add the volume of the nitric acid solution determined above and5ml of the sodium molybdate solution (3.3.7)
47、. Mix thoroughly and allow to stand for15min to25min at20 C to25 C. Then add5ml of the tartaric acid solution (3.3.4),11ml of the sulphuric acid solution (3.3.6) and finally2ml of the ascorbic acid solution (3.3.3). Mix, dilute to the mark with water and mix again. At the same time, carry out a blan
48、k test using20.0ml of the blank solution (3.5.1.1) and dilute to a final volume of100ml. 3.5.2.3 Photometric measurements. After an interval of10min to40min, measure the absorbance of each solution against water, at the wavelength used in the calibration, using4cm cells, and read the amount of silic
49、a present, expressed as SiO 2 , from the calibration graph. If the absorbance is too great for the4cm cells, use1cm cells and the appropriate calibration graph. 3.5 Calculation. Silica content, expressed as a percentage by mass of SiO 2 , is given by the formula: 0.5 (m 1 m 2 ) where m 1is the mass of silica (SiO 2 ) contained in the aliquot portion of the sample solution taken (mg), and m 2is the mass of silica (SiO 2 ) contained in the aliquot portion of the blank solution taken (mg). 4 Determination of fluorine content 4.1 Introduction. This cla
