1、BRITISH STANDARD BS 6070-5: 1981 ISO 5143:1977 Sampling and test for sodium carbonate for industrial use Part 5: Determination of sulphate content ISO title: Sodium carbonate for industrial use Determination of sulphur compounds content Method by reduction and titrimetry NOTEIt is recommended that t
2、his Part be read in conjunction with the information in the “Generalintroduction”, published separately as BS 6070-0. UDC 661.833.622.546.33264:543.24.062:543.226BS6070-5:1981 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the
3、 authorityofthe Executive Boardand comes into effect on 27 February 1981 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference CIC/22 Draft for comment 76/52715 DC ISBN 0 580 12004 X Amendments issued since publication Amd. No. Date of issue CommentsBS6070
4、-5:1981 BSI 12-1999 i Contents Page National foreword ii 1 Scope and field of application 1 2 Reference 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Procedure 2 7 Expression of results 3 8 Test report 3 Annex ISO Publications relating to sodium carbonate for industrial use 6 National appendix Remova
5、l of mercury from waste solutions 7 Figure 1 Typical apparatus for the determination of sulphur compounds 4 Figure 2 Typical apparatus for the preparation of the reducing solution 5 Publications referred to Inside back coverBS6070-5:1981 ii BSI 12-1999 National foreword This Part of BS6070 is identi
6、cal with ISO5143 “Sodium carbonate for industrial use Determination of sulphur compounds content Method by reduction and titrimetry” published in1977 by the International Organization for Standardization (ISO). The National appendix to the Part of this standard describes a procedure to remove mercur
7、y from waste solutions from the analytical procedures described herein. This procedure is technically equivalent to that described in ISO5790“Inorganic chemical products for industrial use General method for determination of chloride content Mercurimetric method” (which has not been implemented as a
8、 British Standard). 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 in British Standards; attention is especially draw
9、n to the following. The comma has been used throughout 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, they should be read as “British Standard”
10、. Cross-reference. There is no British Standard corresponding directly to ISO739 to which reference is made in6.1. Technically equivalent information is given in BS6070-0. NOTEBS 3674 “Specification for sodium carbonate (technical grades)”, gives details for preparing a suitable test portion complyi
11、ng with the requirements of6.1. The standards listed in the Annex are intended for information only. Corresponding British Standards are listed in BS 6070-0. Additional information Water. Water complying with the requirements of clause4 is specified in BS3978“Water for laboratory use”. Hydrochloric
12、acid. approximately1.18g/ml, about36% (m/m) solution, which is the corresponding reagent available in the UK, is suitable for use in place of the solution specified in4.5. WARNING NOTES 1. Mercury (II) nitrate, specified in4.7, is toxic (with danger of cumulative effects) and is irritant, particular
13、ly in the form of dust. Avoid breathing dust. Avoid contact with skin and eyes. Avoid pollution of waste water with mercury from waste solutions using, for example, the procedure for removal of mercury described in the National appendix to this Part of this standard. 2. Hydriodic acid solution, spec
14、ified in4.5, gives off harmful vapour, is toxic, corrosive and irritant. Avoid breathing vapour. Prevent contact with eyes and skin. NOTETextual error. In the first line of4.5 “Place the flask” should be read as “Place in the flask”. A British Standard does not purport to include all the necessary p
15、rovisions 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 cover, pages i and ii, pages1 to 8,
16、 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.BS6070-5:1981 BSI 12-1999 1 1 Scope and field of application This International Standard speci
17、fies a method, by reduction and titrimetry, for the determination of sulphur compounds content of sodium carbonate for industrial use. The method is applicable to products having a sulphur compounds content, expressed as sulphate, equal to or greater than5mg/kg. 2 Reference ISO 739, Sodium carbonate
18、 for industrial use Preparation and storage of test samples. 3 Principle Progressive neutralization, with evolution of carbon dioxide, by adding slowly a mixture of hydriodic acid and hypophosphorous acid. Reduction of sulphur compounds to hydrogen sulphide by heating with this reducing solution. Di
19、stillation of hydrogen sulphide, entrainment in a current of oxygen-free nitrogen and absorption in a mixture of acetone and sodium hydroxide solution. Titration of the sulphide with a standard volumetric mercury(II) nitrate solution in the presence of dithizone as indicator. 4 Reagents During the a
20、nalysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 4.1 Acetone 4.2 Nitrogen, free from oxygen. 4.3 Sodium hydroxide, approximately10N solution. 4.4 Sodium hydroxide, approximately1N solution. 4.5 Reducing solution Place the flask (F) of
21、the apparatus(5.3), swirling after each addition: 50ml of phosphinic (hypophosphorous) acid (H 3 PO 2 ) solution, approximately1,21g/ml, about 50% (m/m) solution; 100ml of hydrochloric acid solution, approximately1,19g/ml, about38% (m/m) solution; 120ml of hydrochloric acid solution, approximately1,
22、97g/ml, about67% (m/m) solution. Assemble the reflux condenser (G), flask (F) and inlet tube (H). Then, while passing a slow stream of the nitrogen(4.2), boil under reflux for4h. Cool to ambient temperature, under a flow of the nitrogen, and store the reagent away from direct sunlight in an amber gl
23、ass bottle, previously purged with the nitrogen, fitted with a ground glass stopper. 4.6 Sodium sulphate, 0,001M (=0,002N) standard reference solution. Weigh, to the nearest0,001g,0,142 0g of anhydrous sodium sulphate, previously dried at110 C and cooled in a desiccator. Transfer quantitatively to a
24、1000ml one-mark volumetric flask, dissolve in water, dilute to the mark and mix. 1ml of this solution corresponds to964g ofSO 4 . 4.7 Mercury(II) nitrate, 0,05M (=0,1N) standard volumetric solution. Weigh10,85 0,01g of mercury(II) oxide (HgO), place in a beaker of suitable capacity (100ml for exampl
25、e) and dissolve in10ml of nitric acid solution, approximately1,40g/ml, about68% (m/m) solution. Dilute the solution, transfer it quantitatively to a1000 ml one-mark volumetric flask, dilute to the mark and mix. 4.8 Mercury(II) nitrate, 0,001 M (=0,002N) standard volumetric solution. Place20,00ml of
26、the standard volumetric mercury(II) nitrate solution (4.7) in a1000ml one-mark volumetric flask, dilute to the mark and mix. Prepare this solution just before use. NOTEThe concentration of the solutions (4.7 and4.8) prepared as described above are sufficiently exact, taking into consideration the sm
27、all amounts of sulphur compounds to be determined. Standardization is therefore unnecessary. In most laboratories, an exactly0,05M (=0,1N) standard volumetric mercury(II) nitrate solution will be available, this solution being commonly used for the mercurimetric determination of chlorides. 4.9 (Phen
28、ylazo)thioformic acid, 2-phenylhydrazide (dithizone), 0,5 g/l solution in the acetone(4.1). Renew this solution after2weeks. 5 Apparatus Ordinary laboratory apparatus and 5.1 Burette (E), of capacity5ml, graduated in0,01ml. 5.2 Apparatus for reduction and distillation, of which all the components ar
29、e fitted together by means of ground glass joints. A typical apparatus is shown inFigure 1 and comprises 5.2.1 Conical flask (A) of capacity100ml. 5.2.2 Reflux condenser (B) 5.2.3 Absorption vessel (C), of height100mm and internal diameter25mm. 5.2.4 Dropping funnel (D), of capacity50ml. SO 2 4 BS60
30、70-5:1981 2 BSI 12-1999 5.2.5 Stopcocks (1), (2) and (3). 5.3 Apparatus for the preparation of the reducing solution (4.5). A typical apparatus is shown inFigure 2 and comprises 5.3.1 Three-necked flask (F), of capacity500ml. 5.3.2 Reflux condenser (G), spiral type. 5.3.3 Inlet tube (H), for nitroge
31、n. 6 Procedure 6.1 Test portion Weigh, to the nearest0,01g, a mass of the test sample (see ISO739) containing not more than5g of Na 2 CO 3into the dried conical flask (A). 6.2 Check test The purpose of this test is to check the gas tightness and functioning of the apparatus(5.2) (reduction of sulphu
32、r compounds and quantitative recovery of the hydrogen sulphide liberated). Place respectively into the absorption vessel (C):5ml of the sodium hydroxide solution(4.4),5ml of the acetone(4.1) and0,1ml of the dithizone solution(4.9); into the dried conical flask (A):2,00ml of the standard reference so
33、dium sulphate solution(4.6) and a few glass beads; into the dropping funnel (D):50ml of the reducing solution(4.5); into the burette (E): the standard volumetric mercury(II) nitrate solution(4.8). Assemble the apparatus(5.2), taking care to smear the ground glass joints lightly with a silicone greas
34、e and to tighten them with suitable clips to ensure perfect gas tightness. Pass the nitrogen(4.2) through stopcock (3) at a rate of about 2 bubbles per second. After5min, run the mercury(II) nitrate solution(4.8), drop by drop, into the absorption vessel (C) until the colour of the indicator changes
35、 from yellow to red. Open stopcocks (1) and (2) in order to allow the reducing solution(4.5) to flow into the conical flask(A), leaving a few millimetres of liquid in the dropping funnel (D), and then close both stopcocks. Start the flow of water through the condenser (B) and, while continuing the n
36、itrogen flow, boil the solution gently in the conical flask (A) for at least30min. The presence of hydrogen sulphide is indicated by a change in colour of the indicator from red to yellow. NOTEDevelopment of a blue-green coloration indicates that a large quantity of hydrochloric acid has been entrai
37、ned and the check test should be repeated. This will only occur exceptionally and will probably result from an accident. If it were, however, to occur on repetition of this test, it would, in that case, be advisable to place one or two wash-bottles containing a100g/l solution of sodium dihydrogenpho
38、sphate monohydrate (NaH 2 PO 4 .H 2 O) between the condenser (B) and the absorption vessel (C) in order to absorb the acid vapours without retaining the hydrogen sulphide. Stop the boiling and, while continuing the flow of nitrogen, titrate the sulphide in the absorption vessel (C) with the standard
39、 volumetric mercury(II) nitrate solution(4.8) contained in the burette (E), until the colour of the indicator changes from yellow to red. The result of the check test is considered satisfactory if the volume of the standard volumetric mercury(II) nitrate solution used for the titration is between1,9
40、0and2,10ml after subtraction of the blank test result (6.3). If low results are obtained, this may be due to the presence of leaks in the apparatus, oxygen in the nitrogen, or exhaustion of the reducing solution. Check these sources of error and repeat the check test until satisfactory results are o
41、btained. 6.3 Blank test Carry out a blank test under the same conditions as the check test(6.2) but using2,00ml of water instead of2,00ml of the standard reference sodium sulphate solution(4.6). 6.4 Determination Carry out the determination under the same conditions as the check test (6.2), subject,
42、 however, to the following amendments: substitute the test portion(6.1) for the2,00ml of the standard reference sodium sulphate solution(4.6); run the reducing solution(4.5) very slowly, drop by drop, into the conical flask (A) in order to avoid sudden evolution of carbon dioxide; place1ml of the so
43、dium hydroxide solution(4.3) in the absorption vessel (C) to render the absorbing solution alkaline before boiling the solution in the conical flask (A).BS6070-5:1981 BSI 12-1999 3 7 Expression of results The sulphur compounds content, expressed as milligrams of sulphateper kilogram, is given by the
44、 formula where 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 in the
45、International Standard to which reference is made, or regarded as optional. V 0 is the volume, in millilitres, of the standard volumetric mercury(II) nitrate solution(4.8) used for the blank test; V 1 is the volume, in millilitres, of the standardvolumetric mercury(II) nitrate solution(4.8) used for
46、 the determination; m is the mass, in grams, of the test portion(6.1); 96is the mass, in micrograms, of SO 4corresponding to1ml of the standard volumetric mercury(II) nitrate solution(4.8). SO 2 4 BS6070-5:1981 4 BSI 12-1999 Figure 1 Typical apparatus for the determination of sulphur compoundsBS6070
47、-5:1981 BSI 12-1999 5 Figure 2 Typical apparatus for the preparation of the reducing solutionBS6070-5:1981 6 BSI 12-1999 Annex ISO Publications relating to sodium carbonate for industrial use ISO 739, Preparation and storage of test samples. ISO 740, Determination of total soluble alkalinity Titrime
48、tric method. ISO 741, Determination of sodium hydrogen carbonate content Titrimetric method. ISO 742, Determination of chloride content Mercurimetric method. ISO 743, Determination of sulphate content Barium sulphate gravimetric method. ISO/R 744, Determination of iron content 2,2-Bipyridyl photomet
49、ric method. ISO 745, Determination of loss of mass and of non-volatile matter at250 C. ISO 746, Determination of matter insoluble in water at50 C. ISO 5143, Determination of sulphur compounds content Method by reduction and titrimetry. BS6070-5:1981 BSI 12-1999 7 National appendix Removal of mercury from waste solutions A.1 Scope This National appendix describes a method for removing mercury from waste solutions in order to prevent pollution of waste water. It is recommended principally
