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1、BRITISH STANDARD BS 6075-4: 1981 ISO 984:1974 Methods of Sampling and test for sodium hydroxide for industrial use Part 4: Determination of silica content ISO title: Sodium hydroxide for industrial use Determination of silica content Reduced silico-molybdic complex photometric method NOTEIt is recom
2、mended that this Part be read in conjunction with the information in the “General introduction” published separately as BS 6075-0. UDC 661.322.1:546.33 36:543.42.062:546.284 31 Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:09:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6075-4:1981 T
3、his British Standard, having been prepared under the direction of the Chemicals Standards Committee, was published under the authority of the Executive Board and comes into effect on 27 February 1981 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference CI
4、C/22 Draft for comment 73/54863 DC ISBN 0 580 12054 6 Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:09:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6075-4:1981 BSI 11-1999i Contents Page National forewordii 1Scope and
5、field of application1 2Reference1 3Principle1 4Reagents1 5Apparatus1 6Procedure2 7Expression of results3 8Test report3 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:09:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6075-4:1981 ii BSI 11-1999 Na
6、tional foreword This Part of BS 6075 is identical with ISO 984 “Sodium hydroxide for industrial use Determination of silica content Reduced silico-molybdic complex photometric method”, published in 1974 by the International Organization for Standardization (ISO). Terminology and conventions. The tex
7、t 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 in British Standards; attention is especially drawn to the following. The comma has been used throughout a
8、s 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, they should be read as “British Standard”. Additional information Water. Water complying with the
9、 requirements of clause 4 is specified in BS 3978 “Water for laboratory use”. Calibration graph. For some grades of sodium hydroxide it may be necessary to adjust the range of the calibration graph (see 6.3) to cover the expected silica content. In BS 4130 “Sodium hydroxide (technical grades)” detai
10、ls of a suitable range for the grades specified are given. A British Standard does not purport 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 l
11、egal obligations. Cross-reference International StandardCorresponding British Standard BS 6075 Methods of sampling and test for sodium hydroxide for industrial use ISO 3195:1975Part 5:1981 Sampling and preparation of main test solution (Identical) Summary of pages This document comprises a front cov
12、er, an inside front cover, pages i and ii, pages 1 to 4, 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. Licensed Copy: sheffieldun sheffieldu
13、n, na, Wed Dec 06 14:09:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6075-4:1981 BSI 11-19991 1 Scope and field of application This International Standard specifies a reduced silico-molybdic complex photometric method for the determination of the silica content of sodium hydroxide for industrial
14、 use. The method is applicable to products having silica (SiO2) contents exceeding 10 mg/kg. 2 Reference ISO 3195, Sodium hydroxide for industrial use Sampling Test sample Preparation of the main solution for carrying out certain determinations1). 3 Principle Formation of the yellow oxidized silico-
15、molybdic complex at pH 1,1 0,2, in the presence of boric acid to suppress interference by fluorides. Selective reduction of this complex with a mixture of amino-naphthol sulphonic acid (4-amino-3-hydroxynaph-thalene-1-sulphonic acid), sodium metabisulphite and sodium sulphite, in the presence of oxa
16、lic acid and in a strongly acid medium so as to suppress interference by phosphates. Photometric measurement of the blue-coloured complex at a wavelength of about 795 nm. 4 Reagents During the analysis use only reagents of recognized analytical reagent grade and only demineralized water. Store all t
17、he reagents in polyethylene bottles. 4.1 Sulphuric acid, approximately 9 N solution. 4.2 Hydrochloric acid, approximately 2 N solution. 4.3 Boric acid, saturated solution (about 48 g/l). 4.4 Oxalic acid, 100 g/l solution. 4.5 Sodium molybdate dihydrate Na2MoO4.2H2O, 140 g/l solution. Dissolve 35 g o
18、f this reagent in 200 ml of water at about 50 C in a polyethylene beaker. Cool to room temperature, transfer to a 250 ml one-mark volumetric flask, dilute to the mark and mix. Transfer to a polyethylene bottle. If necessary, filter the solution before use. 4.6 Reducing solution 4.6.1 Dissolve 7 g of
19、 anhydrous sodium sulphite in 50 ml of water. Then add 1,5 g of 4-amino-3-hydroxynaphthalene-1-sulphonic acid and dissolve by trituration. 4.6.2 Dissolve 90 g of anhydrous sodium metabisulphite in 900 ml of water. Mix the two solutions (4.6.1) and (4.6.2) and dilute to 1 000 ml. Filter, if necessary
20、, store the solution in a cool place away from direct sunlight and renew it every 15 to 20 days. 4.7 Sodium chloride, 70 g/l solution. 4.8 Silica, standard solution corresponding to 0,500 g of SiO2 per litre. In a platinum crucible, weigh, to the nearest 0,001 g: either 0,500 g of silica (SiO2) prod
21、uced from silicic acid (H2SiO3) calcined at 1 000 C to constant mass and cooled in a desiccator; or 0,500 g of pure quartz, finely ground and previously calcined for 1 h at 1 000 C and cooled in a desiccator. Add 5 g of anhydrous sodium carbonate to the crucible. Mix well, preferably with a platinum
22、 spatula, and fuse carefully. Allow to cool, add warm water, heat moderately until completely dissolved, cool, transfer quantitatively to a 1 000 ml one-mark volumetric flask, dilute to the mark and mix. Transfer immediately to a polyethylene bottle. 1 ml of this standard solution contains 0,500 mg
23、of SiO2. 4.9 Silica, standard solution corresponding to 10 mg of SiO2 per litre. Take 20,0 ml of the standard silica solution (4.8), transfer into a 1 000 ml one-mark volumetric flask, dilute to the mark and mix. 1 ml of this standard solution contains 0,010 mg of SiO2. Prepare this standard solutio
24、n at the time of use. 4.10 Phenolphthalein, 10 g/l solution in 95 % (V/V) ethanol. 5 Apparatus Ordinary laboratory apparatus and 5.1 Spectrophotometer or 5.2 Photoelectric absorptiometer with 2 cm cells and fitted with suitable filters ensuring a maximum transmission at about 795 nm. NOTEIf such fil
25、ters are not available, operate at about 680 nm, with 4 cm cells. 1) At present at the stage of draft. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:09:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6075-4:1981 2 BSI 11-1999 6 Procedure 6.1 Test portion 6.1.1 Weigh, to the nearest 0,01
26、 g, in a 100 ml polyethylene beaker, 13 0,1 g of the solution A (see 4.3 of ISO 3195) stored in a silica-free vessel and containing 40 g of the test sample in 1 000 ml. During this operation, prevent the solution from coming into contact with glass. 6.1.2 In addition, determine the mass, to the near
27、est 0,01 g, of 10,0 ml of the solution A, taken with the aid of a pipette or a burette, to enable the mass of the test portion (6.1.1) to be converted to a volume when the results are calculated. 6.2 Blank test Carry out a blank test at the same time as the determination, following the same procedur
28、e and using the same quantities of all the reagents used for the determination (6.4) but replacing the 10,0 ml of the solution A by 10,0 ml of the sodium chloride solution (4.7). 6.3 Preparation of calibration curve 6.3.1 Preparation of the standard colorimetric solution, for photometric measurement
29、s with 2 cm cells at a wavelength of about 795 nm or with 4 cm cells for photometric measurements at about 680 nm. Into a series of four 100 ml polyethylene beakers, introduce the volumes of the standard silica solution (4.9) shown in the following table: Treat the contents of each beaker as follows
30、. Add 10,0 ml of the sodium chloride solution (4.7), dilute to 25 ml and add, swirling after each addition, 7,5 ml of the hydrochloric acid solution (4.2), 20 ml of the boric acid solution (4.3) and 10 ml of the sodium molybdate solution (4.5). The pH of the solution should now be about 1,1. Wait 10
31、 min and then add, swirling after each addition, 5 ml of the oxalic acid solution (4.4) and 20 ml of the sulphuric acid solution (4.1). Allow to stand for 2 min, then add 2 ml of the reducing solution (4.6), transfer quantitatively to a 100 ml one-mark volumetric flask, dilute to the mark and mix. 6
32、.3.2 Photometric measurements After at least 10 min, but not more than 40 min, carry out the photometric measurements using the spectrophotometer (5.1), at a wavelength of about 795 nm, or the photoelectric absorptiometer (5.2), fitted with suitable filters, after having adjusted the instrument to z
33、ero absorbance against the compensation solution. 6.3.3 Preparation of the calibration chart Plot a graph having, for example, the numbers of milligrams of silica (SiO2) contained in 100 ml of standard colorimetric solutions on the abscissa and the corresponding values of absorbance on the ordinate.
34、 6.4 Determination 6.4.1 Colour development Add 1 drop of the phenolphthalein solution (4.10) to the test portion (6.1), already contained in a 100 ml polyethylene beaker, and neutralize with the hydrochloric acid solution (4.2). Add 10 ml of water and, swirling after each addition, 7,5 ml of the hy
35、drochloric acid solution (4.2), 20 ml of the boric acid solution (4.3) and 10 ml of the sodium molybdate solution (4.5). Wait for 10 min then add, swirling after each addition, 5 ml of the oxalic acid solution (4.4) and 20 ml of the sulphuric acid solution (4.1). Allow to stand for 2 min, then add 2
36、 ml of the reducing solution (4.6), transfer quantitatively to a 100 ml one-mark volumetric flask, dilute to the mark and mix. 6.4.2 Photometric measurement After at least 10 min, but not more than 40 min, carry out the photometric measurement according to the procedure specified in 6.3.2, after hav
37、ing adjusted the instrument to zero absorbance against the blank test solution (6.2). Standard silica solution (4.9) Corresponding mass of SiO2 mlmg 0a 2,0 5,0 10,0 0 0,02 0,05 0,10 a Compensation solution Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:09:37 GMT+00:00 2006, Uncontrolled C
38、opy, (c) BSI BS 6075-4:1981 BSI 11-19993 7 Expression of results By means of the calibration curve (6.3.3), determine the quantity of SiO2 corresponding to the value of the photometric measurement. The silica content, expressed as milligrams of silica (SiO2) per kilogram, is given by the formula whe
39、re m0is the mass, in grams, of the test sample used to prepare solution A; m1is the mass, in milligrams, of SiO2 found by the determination; m2is the mass, in grams, of the test portion (6.1.1); m3is the mass, in grams, of 10,0 ml of solution A (see 4.3 of ISO 3195), determined by the procedure spec
40、ified in 6.1.2. 8 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 the In
41、ternational Standard to which reference is made, or regarded as optional. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:09:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 4 blank Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:09:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6
42、075-4:1981 BSI 11-1999 Publications referred to See national foreword. Licensed Copy: sheffieldun sheffieldun, na, Wed Dec 06 14:09:37 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6075-4: 1981 ISO 984:1974 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the indepen
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