1、BRITISH STANDARD BS 6075-2: 1981 ISO 981:1973 Methods of Sampling and test for sodium hydroxide for industrial use Part 2: Determination of chloride content (mercurimetric method) ISO title: Sodium hydroxide for industrial use Determination of chloride content Mercurimetric method NOTEIt is recommen
2、ded 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 36:543.24.062:546.131BS6075-2:1981 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published u
3、nder the authority ofthe Executive Board and comesinto effect on 27 February 1981 BSI 10-1999 The following BSI reference relates to the work on this standard: Committee reference CIC/22 ISBN 0 580 12052 X Amendments issued since publication Amd. No. Date of issue CommentsBS6075-2:1981 BSI 10-1999 i
4、 Contents Page National foreword ii 1 Scope 1 2 Field of application 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Procedure 1 7 Expression of results 2 8 Test report 2 National appendix A Removal of mercury from waste solutions 3 A.1 Scope 3 A.2 Principle 3 A.3 Reagents 3 A.4 Apparatus 3 A.5 Procedu
5、re 3 Publications referred to Inside back coverBS6075-2:1981 ii BSI 10-1999 National foreword This Part of BS 6075 is identical with ISO 981 “Sodium hydroxide for industrial use Determination of Chloride content Mercurimetric method”, published in1973 by the International Organization for Standardiz
6、ation (ISO). The National appendix A to this Part of this standard describes a procedure to remove mercury from waste solutions from the analytical procedures described herein. This procedure is technically equivalent to that described in ISO 5790 “Inorganic chemical products for industrial use Gene
7、ral method for determination of chloride content Mercurimetric method” (which has not been implemented as a 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 a
8、nd certain conventions are not identical with those used in British Standards; attention is especially drawn 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 w
9、ords “International Standard” appear, referring to this standard, they should be read as “British Standard”. Additional information Water. Water complying with the requirements of clause 4 is specified in BS3978 “Water for laboratory use”. Reagents. The reagents used shall be of recognized analytica
10、l quality. Test portion. For some grades of sodium hydroxide it may be necessary to adjust the mass of the test portion (see 6.1) to ensure that the amount of chloride present in the test solution complies with the requirements for the test method. In BS4130 “Sodium hydroxide (technical grades)” det
11、ails of a suitable mass for the grades specified are given. WARNING. Mercury (II) nitrate, specified in 4.6, is toxic (with danger of cumulative effects) and is irritant, particularly in the form of dust. Avoid breathing dust. Avoid contact with skin and eyes. Avoid pollution of waste water with mer
12、cury from waste solutions using, for example, the procedure for removal of mercury described in the National appendix A to this Part of this standard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their corre
13、ct 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 4, an inside back cover and back cover. This standard has been updated (see copyright
14、 date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6075-2:1981 BSI 10-1999 1 1 Scope This International Standard specifies a mercurimetric method for the determination of the chloride content of sodium hydroxide for industrial u
15、se. 2 Field of application The method is applicable to products of which the sodium chloride content is greater than 0,005 % (m/m). NOTEIf 0,02 N standard volumetric mercury(II) nitrate is used, the method is applicable to products of which the sodium chloride content is greater then 0,002 % (m/m).
16、3 Principle Titration of the Cl ion with mercury(II) nitrate in the presence of diphenylcarbazone as indicator. 4 Reagents Distilled water or water of equivalent purity shall be used in the test. 4.1 Nitric acid, 1,40 g/ml, approximately 68 % (m/m) or approximately14Nsolution, of which the chloride
17、content, expressed as Cl, is not greater than 1 mg/kg. 4.2 Nitric acid, approximately 2 N solution. 4.3 Sodium hydroxide, 7,5 % (m/m) or approximately 2 N solution. 4.4 Sodium chloride, 0,05 N standard reference solution 1) . Weigh, to the nearest 0,1 mg, 2,922 1 g of sodium chloride, previously dri
18、ed for 1 h at 500 C and cooled in a desiccator. Dissolve it in water in a1000ml one-mark volumetric flask, dilute to the mark and mix. 4.5 Standard end-point matching solution Prepare this standard solution immediately before use. Pour 200 ml of water into a 500 ml conical flask, add 3 drops of the
19、bromophenol blue solution (4.7), and then add the nitric acid solution (4.2), drop by drop, until the colour changes from blue to yellow. Add an excess of 3 drops of this acid, 0,5 to 1,0 ml of the diphenylcarbazone solution (4.8) and (from a burette) the volume of the standard volumetric mercury(II
20、) nitrate solution (4.6) necessary to change the colour of the solution from yellow to mauve (2 drops). 4.6 Mercury(II) nitrate, 0,05 N standard volumetric solution. 4.6.1 Preparation of the solution Weigh 5,43 0,01 g of mercury(II) oxide (HgO) and dissolve it in 10 ml of the nitric acid solution (4
21、.1) in a 1 000 ml one-mark volumetric flask, dilute to the mark and mix. Standardize this solution following the procedure described in 4.6.2, adjusting it to the exact concentration, if necessary. NOTEAnalysts who can detect easily the diphenylcarbazone colour change can take advantage of a 0,02 N
22、standard volumetric solution (2,18 g of HgO in 1 000 ml, standardized against a standard reference solution of sodium chloride containing 1,168 8 g of NaCl in 1 000 ml) in order to increase the sensitivity of the method. 4.6.2 Standardization of the solution Transfer 40,0 ml of the sodium chloride s
23、tandard reference solution (4.4) to a 500 ml conical flask, followed by 160 ml of water and 3 drops of the bromophenol blue solution (4.7). Add drop by drop the nitric acid solution (4.2) until the colour of the indicator changes from blue to yellow, then add an excess of 3 drops of this acid and a
24、volume of the diphenylcarbazone solution (4.8) identical to that added for the standard end-point matching solution(4.5). Titrate the chloride with the mercury(II) nitrate solution to be standardized(4.6.1) until the colour matches the mauve of the standard end-point matching solution(4.5) and deduc
25、t the volume of the mercury(II) nitrate solution (4.6.1) added during the preparation of this standard end-point matching solution (2 drops). The correct amount is 40,00 ml. 4.7 Bromophenol blue, 1 g/l solution in 95 % (V/V) ethanol. 4.8 Diphenylcarbazone, 5 g/l solution in 95 % (V/V) ethanol. Store
26、 this solution in a refrigerator and replace it when it no longer gives a sharp colour change. 5 Apparatus Ordinary laboratory apparatus. 6 Procedure 6.1 Test portion In a weighing bottle fitted with a stopper weigh, to the nearest 0,1 g, a quantity of the solid or liquid test sample corresponding t
27、o 20 g of NaOH. 1) See note to 4.6.1.BS6075-2:1981 2 BSI 10-1999 6.2 Determination 6.2.1 Preparation of the test solution Transfer the test portion (6.1) to a 500 ml conical flask. Add 100 ml of water and then, cautiously,30ml of the nitric acid solution (4.1). Cool to room temperature, add 3 drops
28、of the bromophenol blue solution (4.7), then add the nitric acid solution (4.1) until the colour changes from blue to yellow. Add the sodium hydroxide solution (4.3) drop by drop until the colour changes to blue, then the nitric acid solution (4.2) until the colour turns yellow and finally an excess
29、 of 3 drops of this acid. Dilute to about 200 ml. 6.2.2 Titration Add to the resultant solution a volume of the diphenylcarbazone solution (4.8) identical to that added for the standard end-point matching solution(4.5), and titrate the chloride with the standard volumetric mercury(II) nitrate soluti
30、on(4.6) until the colour matches the mauve of the standard end-point matching solution (4.5). NOTEDifferent operating conditions for standardizing the mercury(II) nitrate solution and for making the determination are only justified in cases where the chloride content to be determined is low. In othe
31、r cases this would not be so, and the standardization and the determination should then be carried out in conditions as nearly alike as possible. 7 Expression of results The chloride content, expressed as sodium chloride (NaCl), is given, as a percentage by mass, by the formula where m is the mass,
32、in grams, of the test portion; V 0is the volume, in millilitres, of the standard volumetric mercury(II) nitrate solution (4.6) used for the titration; V 1is the volume, in millilitres, of the standard volumetric mercury(II) nitrate solution (4.6) used in the preparation of the standard end-point mat
33、ching solution (4.5); 0,002 922 is the mass, in grams, of sodium chloride corresponding to 1 ml of the standard volumetric mercury(II) nitrate solution (4.6). Express the result to two places of decimals. NOTEIf 0,02 N solutions of mercury(II) nitrate and sodium chloride are used, the formula become
34、s 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 regarded as optiona
35、l.BS6075-2:1981 BSI 10-1999 3 National appendix A Removal of mercury from waste solutions A.1 Scope This National appendix A describes a method for removing mercury from waste solutions in order to prevent pollution of waste water. It is recommended principally for waste solutions from titrations us
36、ing mercury (II) nitrate solution but may be used for other solutions containing mercury. A.2 Principle The mercury in the collected waste solution is precipitated by reaction with alkaline sodium sulphide. Hydrogen peroxide is added to oxidize excess sodium sulphide (to prevent formation of soluble
37、 mercury polysulphides), the insoluble mercury salts are removed by decantation and filtration and the mercury-free waste solution is discarded. A.3 Reagents The following reagents to be used shall be of technical quality. A.3.1 Disodium sulphide nonahydrate, (Na 2 S.9H 2 O). A.3.2 Hydrogen peroxide
38、, approximately 30 % (m/m) solution. A.3.3 Sodium hydroxide, approximately 400 g/l solution. A.4 Apparatus The following apparatus is required. A.4.1 Polyethylene container. A container of 50 litres capacity is suitable. A.4.2 Small laboratory pump or water pump, with a suction tube the end of which
39、 is fitted with a sintered glass disc, grade No 4 (maximum pore diameter 5 4m to 15 4m) complying with the requirements of BS 1752 “Laboratory sintered or fritted filters” or a funnel containing cotton wool. A.5 Procedure Pour the waste solutions into the container (A.4.1). When about 40 litres of s
40、olution has been collected, add successively, mixing by means of compressed air, 400 ml of the sodium hydroxide solution(A.3.3),100 g of the sodium sulphide(A.3.1) and, after 10 min, slowly, 400 ml of the hydrogen peroxide solution (A.3.2). Allow to stand for 24 h, then draw off the clear liquid usi
41、ng the pump (A.4.2) and discard as drain water. Rinse the container several times with sufficient water to transfer the insoluble residue to another container reserved for its storage and subsequent disposal in a manner suitable for material containing mercury.4 blankBS6075-2:1981 BSI 10-1999 Public
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