1、BRITISH STANDARD CONFIRMED JUNE1993 BS6337-2: 1983 ISO6382:1981 General methods of chemical analysis Part 2: Method for determination of silicon content (reduced molybdosilicate spectrophotometric method) ISO title: General method for determination of silicon content Reduced molybdosilicate spectrop
2、hotometric method UDC 543.422.062:546.284BS6337-2:1983 This British Standard, having been prepared under the directionof the Chemical Standards Committee, waspublished under the authorityofthe Board ofBSIandcomes into effect on 31 January1983 BSI11-1999 The following BSI references relate to the wor
3、k on this standard: Committee reference CIC/- Draft for comment79/55177 DC ISBN 0 580 13151 3 Cooperating organizations The Chemical Standards Committee, under whose direction this BritishStandard was prepared, consists of representatives from the following: Association of Fatty Acid Distillers Brit
4、ish Tar Industry Association Chemical Industries Association* Consumer Standards Advisory Committee of BSI Department of Health and Social Security Department of Industry (Laboratory of the Government Chemist) Fertiliser Manufacturers Association Ltd. Ministry of Agriculture, Fisheries and Food Mini
5、stry of Defence* National Sulphuric Acid Association Paintmakers Association of Great Britain Ltd. Royal Institute of Public Health and Hygiene Royal Society of Chemistry Soap and Detergent Industry Association Standardization of Tar Products Tests Committee The organizations marked with an asterisk
6、 in the above list, together with coopted members nominated by other BSI committees, were directly represented on the Technical Committee entrusted with the preparation of this British Standard. Amendments issued since publication Amd. No. Date of issue CommentsBS6337-2:1983 BSI 11-1999 i Contents P
7、age Cooperating organizations Inside front cover National foreword ii 1 Scope 1 2 Field of application 1 3 Principle 1 4 Reagents 1 5 Apparatus 2 6 Procedure 2 7 Expression of results 3 8 Test report 3 Annex A Interferences 5 Annex B Other publications of ISO/TC47 relating to determination of silico
8、n content by reduced molybdosilicate photometry 5 Publications referred to Inside back coverBS6337-2:1983 ii BSI 11-1999 National foreword This Part of BS6337 is the second of a series of general methods of chemical analysis prepared under the direction of the Chemical Standards Committee. It is ide
9、ntical with ISO6382:1981 “General method for determination of silicon content Reduced molybdosilicate spectrophotometric method”, published by the International Organization for Standardization (ISO). For some years, the UK has participated in the work of Subcommittee1 General methods, of Technical
10、Committee47 Chemistry of ISO. As international agreement is reached on the methods, it is proposed to publish them as Parts of this British Standard. The work of Subcommittee1 on such general methods was motivated by the existence of a multiplicity of methods for the same determination, all differin
11、g to various degrees, that had been prepared by the ISO/TC47 sub-committees, etc., responsible for particular chemical products or groups of products. For this historical reason, unnecessary proliferation of different reagents, apparatus and procedures had been developed. These general methods are i
12、ntended to reduce such proliferation, as far as is possible. They assume that a suitable test solution of a product to be analyzed has been prepared, by a method established in the standard relating to the product concerned, which also gives other specific details such as relevant interfering specie
13、s and how to overcome them, and how the results should be expressed. It is hoped and expected that any committees that wish to revise existing, or prepare new, standards involving an analysis corresponding to the general methods, will do so by no more than cross-references to the appropriate parts o
14、f this BritishStandard. Because a general method cannot take into account the properties of all the products to which it may be applied, it should indicate what characteristics the test solution should have in order that the method can be applied to it. The compiler of the product standard should in
15、dicate how the test portion is to be treated in order to obtain a test solution with the required characteristics. Moreover, while a general method should include a list of known interferences, together with suggestions by which they can be overcome, the product standard should indicate what interfe
16、rences might be expected in a particular product and what action should be taken if they are present so that the general method can be applied to the product concerned. Because no product standard can be expected to foresee all eventualities, the user of the product standard should check in all case
17、s that the general method will be applicable to a particular material. Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used
18、 in British Standards; attention is especially drawn to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard” appear, referring to this standard, t
19、hey should be read as “British Standard”. Cross-references. The corresponding British Standards for the ISO publications relating to determination of silicon content by reduced molybdosilicate photometry, which are listed in Annex B for information only, are as follows. International Standard Corres
20、ponding British Standard ISO984:1974 BS6075 Methods of sampling and test for sodium hydroxide for industrial use Part4 Determination of silica content (Identical)BS6337-2:1983 BSI 11-1999 iii A British Standard does not purport to include all the necessary provisions of a contract. Users of British
21、Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. International Standard Corresponding British Standard ISO995:1975 BS5634 Methods of test for potassium hydroxide (Related) ISO1232:1976 BS4140 Method
22、s of test for aluminium oxide (Related) ISO1620:1976 BS5050 Methods of test for cryolite (Related) ISO2369:1972 BS4993 Methods of test for aluminium fluoride for industrial use Part3 Determination of silica content (Related) ISO3361:1975 BS4258 Methods of test for phosphoric acid (orthophosphoric ac
23、id) for industrial use Part5 Determination of silica content (Related) ISO3540:1976 BS5072 Methods of test for sodium fluoride for industrial use Part6 Determination of silica content (Identical) ISO3701:1976 BS5365 Methods of sampling and test for anhydrous hydrogen fluoride for industrial use Part
24、4 Determination of hexafluorosilicic content (Identical) ISO5438 a BS5659 Methods of test for acid-grade fluorspar Part8 aDetermination of silica content a In course of preparation. Summary of pages This document comprises a front cover, an inside front cover, pagesi to iv, pages1to6, an inside back
25、 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.iv blankBS6337-2:1983 BSI 11-1999 1 WARNING Attention is drawn to the dangers involved in the use of some of
26、the reagents (see the corresponding notes). 1 Scope This International Standard specifies a general method for the determination of silicon by spectrophotometric measurement of reduced molybdosilicate. It describes a technique for the determination of the content of silicon in a solution. Reference
27、should be made, for the preparation of the test solution, to the International Standard relating to the product to be analysed, which should indicate the modifications necessary to make the method applicable to that product. 2 Field of application The method is applicable to the determination of qua
28、ntities of silicon, expressed as SiO 2 , between2 and2004g in the aliquot portion of the test solution taken for the determination. The ions, elements and compounds given in the table in Annex A do not interfere with the determination when they are present separately up to the limits indicated. In c
29、ertain cases, this table gives guidance on the treatment to be applied to reduce or suppress interferences. 3 Principle Depolymerization of any polymerized silica by treatment with sodium fluoride in the presence of hydrochloric acid. Formation of the oxidized (yellow) molybdosilicate at a pH of1,1
30、0,2in the presence of boric acid to suppress interference by fluoride ion. Selective reduction of this complex in the presence of oxalic acid and in a sulphuric acid medium of acidity sufficiently high to eliminate interference by phosphates. Spectrophotometric measurement of the blue-coloured compl
31、ex at the wavelength corresponding to maximum absorption (about800nm). 4 Reagents During the analysis, use only reagents of recognized analytical grade, as far as possible silica-free, and water which has been double-distilled from a quartz apparatus or water of equivalent purity. NOTEDemineralized
32、water is not suitable. Store all the reagents in flasks of material free from silica (for example, polyethylene). 4.1 Sulphuric acid, approximately400g/l solution. Add, taking all necessary precautions,240ml of sulphuric acid, 1,84g/ml 98% (m/m) solution, to500ml of water, dilute to1000ml and mix. 4
33、.2 Hydrochloric acid, approximately150g/l solution. Dilute, taking all necessary precautions,340ml of hydrochloric acid, 1,19g/ml 38% (m/m) solution, to1000ml with water. 4.3 Boric acid, solution saturated at room temperature (approximately48g/l). 4.4 Oxalic acid dihydrate (COOH) 2 .2H 2 O,100g/l so
34、lution. NOTEHarmful in contact with skin and if swallowed. Avoid contact with skin and eyes. 4.5 Sodium fluoride, 20g/l solution. Store this solution in a flask of material free from silica. NOTEToxic by inhalation, in contact with skin and if swallowed. In case of contact with eyes, rinse immediate
35、ly with plenty of water and seek medical advice. In case of feeling unwell, seek medical advice (show the label where possible). 4.6 Disodium molybdate dihydrate, 140g/l solution. Dissolve, in a polyethylene beaker,35g of disodium molybdate dihydrate (Na 2 MoO4.2H 2 O) in200ml of water at about50 C.
36、 Allow to cool to ambient temperature, transfer to a250ml one-mark volumetric flask and dilute to the mark. Transfer the solution to a flask of material free from silica and, if necessary, filter before use. Prepare this solution at the time of use. 4.7 Reducing solution Use one of the following sol
37、utions: 4.7.1 4-amino-3-hydroxynaphthalene-1-sulphonic acid, 1,5g/l solution. a) Dissolve7g of anhydrous sodium sulphite (Na 2 SO 3 ) in50ml of water. Then add1,5g of4-amino-3-hydroxynaphthalene-1-sulphonic acid (C 10 H 9 NO 4 S) and dissolve with trituration. b) Dissolve90g of anhydrous disodium di
38、sulphite (Na 2 S 2 O 5 ) in900ml of water. Mix the two solutionsa) andb) and dilute to1000ml. Filter if necessary, and store the solution in a dark flask of material free from silica. Renew this solution every2 or3 weeks. NOTEIrritating to skin and eyes. 4.7.2 L-ascorbic acid, 25g/l solution. Dissol
39、ve2,5g of L-ascorbic acid in water, dilute to100ml and mix. Prepare this solution at the time of use. 4.8 Silica, standard solution corresponding to0,500g of SiO 2per litre.BS6337-2:1983 2 BSI 11-1999 In a platinum dish, weigh, to the nearest0,001g, either0,500g of silica (SiO 2 ) obtained by heatin
40、g pure silicic acid at1000 C to constant mass (that is until two consecutive weighings do not differ by more than1mg) and allowed to cool in a desiccator containing diphosphorus pentaoxide, or 0,500g of pure silica, finely ground and previously heated for1h at1000 C and allowed to cool in a desiccat
41、or containing diphosphorus pentaoxide. Add5g of anhydrous sodium carbonate to the dish. Mix well, preferably with a platinum spatula, and fuse carefully until a clear and transparent melt is obtained. Allow to cool, add warm water, heat gently until completely dissolved and transfer the solution qua
42、ntitatively to a beaker of material free from silica. Allow to cool again, dilute the solution to about500ml, transfer quantitatively to a1000ml one-mark volumetric flask, dilute to the mark and mix. Transfer the solution immediately to a flask of material free from silica. 1ml of this solution cont
43、ains0,500mg of SiO 2 . Do not keep this solution for longer than1month. 4.9 Silica, standard solution corresponding to0,010g of SiO 2per litre. Take20,0ml of the standard silica solution(4.8), place in a1000ml one-mark volumetric flask, dilute to the mark and mix. 1ml of this solution contains104g o
44、f SiO 2 . Prepare the solution at the time of use. 5 Apparatus Ordinary laboratory apparatus, and in particular material free from silica (see the note). 5.1 pH meter, fitted with a glass measuring electrode and a calomel reference electrode, calibrated at pH1,1 using hydrochloric acid solution, c(H
45、Cl)=0,1mol/l. 5.2 Spectrophotometer, fitted with cells of optical path length10 or20 or50mm NOTEAll the steps using alkaline solutions and any treatment involving the sodium fluoride solution(4.5) should be carried out in vessels free from silica (for example, polyethylene). Glass volumetric flasks
46、can be used for dilutions if the glass is in good condition (neither chipped nor etched) and if the solutions are transferred immediately into flasks of material free from silica. 6 Procedure 6.1 Test portion and preparation of the test solution The mass of the test portion and the details for prepa
47、ration of the test solution are given in the International Standard relating to the product concerned. NOTEThe pH of the test solution should be between4 and7 except in the presence of hydrolizable salts when the pH adjustment is carried out during the procedure. 6.2 Blank test Carry out a blank tes
48、t at the same time as the determination, using the same procedure and the same quantities of all the reagents (including the sodium fluoride solution and the aliquot portions of neutralizing solutions of the test solution) as used for the determination, but omitting the test portion. 6.3 Preparation
49、 of the calibration graph 6.3.1 Preparation of calibration solutions, for spectrophotometric measurements carried out with cells of optical path length10 or20 or50mm According to the expected silica content of the test solution, place the volumes of the standard silica solution(4.9), shown in the following table, in a series of100ml beakers of material free from silica. Expected silica content of the test solution, 4g 2to30 10to80 50to200 Standard silica solution(4.9) Corresponding mass of SiO 2 Standard silica solution(4.9) Corresponding mass of SiO 2
