1、BRITISH STANDARD BS 6075-8: 1981 ISO 3198:1975 Methods of Sampling and test for sodium hydroxide for industrial use Part 8: Determination of sulphate content ISO title: Sodium hydroxide for industrial use Determination of sulphur compounds Method by reduction and titrimetry NOTEIt is recommended tha
2、t 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 36:543.24.062:546.226BS6075-8:1981 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under th
3、e 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 12058 9 Amendments issued since publication Amd. No. Date of issue CommentsBS6075-8:1981 BSI 10-1999 i Conten
4、ts 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 2 8 Test report 3 Annex ISO publications relating to sodium hydroxide for industrial use 6 National appendix Removal of mercury from waste solu
5、tions 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 coverBS6075-8:1981 ii BSI 10-1999 National foreword This Part ofBS6075 is identical withISO3198 “Sodium hydro
6、xide for industrial use Determination of sulphur compounds Method by reduction and titrimetry”, published in 1975 by the International Organization for Standardization (ISO). The National appendix to this Part of this standard describes a procedure to remove mercury from waste solutions from the ana
7、lytical procedures described herein. This procedure is technically equivalent to that described inISO5790 “Inorganic chemical products for industrial use General method for determination of chloride content Mercurimetric method” (which has not been implemented as a British Standard). Terminology and
8、 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 drawn to the following. The comma has b
9、een 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”. The standards listed in the Annex
10、 are intended for information only. Corresponding British Standards are listed inBS6075-0. Additional information Water. Water complying with the requirements of clause4 is specified inBS3978 “Water for laboratory use”. Hydrochloric acid, approximately 1.18 g/ml, about36% (m/m) solution, which is th
11、e corresponding reagent available in the UK, is suitable for use in place of the solution specified in4.6. Test portion. For some grades of sodium hydroxide it may be necessary to adjust the mass of the test portion (see6.1) to ensure that the amount of sulphur compounds present in the test solution
12、 complies with the requirements for the test method. InBS4130 “Sodium hydroxide (technical grades)”, details of a suitable mass for the grades specified are given. WARNINGS Mercury (II) chloride and mercury (II) nitrate, specified in4.4 and4.8 respectively are toxic (with danger of cumulative effect
13、s) and are irritant particularly in the form of 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. Cross-reference Internat
14、ional Standard Corresponding British Standard BS 6075 Methods of sampling and test for sodium hydroxide for industrial use BS 3195:1975 Part 5:1981 Sampling and preparation of main test solution (Identical)BS6075-8:1981 BSI 10-1999 iii Hydriodic acid solution, specified in4.6, gives off harmful vapo
15、ur and is toxic, corrosive and irritant. Avoid breathing vapour. Prevent contact with eyes and skin. 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
16、 does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1to 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. T
17、his will be indicated in the amendment table on the inside front cover.iv blankBS6075-8:1981 BSI 10-1999 1 1 Scope and field of application This International Standard specifies a reduction and titrimetric method for the determination of sulphur compounds in sodium hydroxide for industrial use. The
18、method is applicable to products of which the content of sulphur compounds, expressed as sulphate (SO 4 ), is equal to or greater than5mg/kg. 2 Reference ISO 3195, Sodium hydroxide for industrial use Sampling Test sample Preparation of the main solution for carrying out certain determinations. 3 Pri
19、nciple Reduction of the sulphur compounds to hydrogen sulphide by heating with a mixture of hydriodic acid and hypophosphorous acid. Absorption of the hydrogen sulphide, entrained in a current of oxygen-free nitrogen, in a mixture of sodium hydroxide and acetone. Titration of the sulphide with stand
20、ard volumetric mercury (II) nitrate solution in the presence of dithizone as indicator. 4 Reagents During the analysis, use only reagents of recognized analytical reagent grade and only distilled water or water of equivalent purity. 4.1 Acetone 4.2 Nitrogen, oxygen-free. 4.3 Sodium hydroxide, approx
21、imately1N solution. 4.4 Potassium permanganate and mercury (II) chloride solution, to purify the nitrogen (4.2). Dissolve first2g of potassium permanganate(KMnO 4 ) and then7g of mercury(II) chloride (HgCl 2 ), in100ml of water and filter the solution. 4.5 Pyrogallol solution, to purify the nitrogen
22、 (4.2). Dissolve15g of pyrogallol in25ml of water and add, while cooling, 150ml of a30% (m/m) potassium hydroxide solution. 4.6 Reduction solution Place in the flask (J) of the apparatus (5.3), shaking after each addition: 50 ml of hypophosphorous acid (H 3 PO 2 ), approximately1,21g/ml, about50% (m
23、/m) solution; 100 ml of hydrochloric acid, approximately1,19g/ml, about38% (m/m) solution; 120 ml of hydriodic acid, approximately1,97g/ml, about67% (m/m) solution. Assemble the flask and the reflux condenser (K) then, while passing a slow flow of the nitrogen (4.2), boil for4h. Cool to room tempera
24、ture under a flow of the nitrogen (4.2) and store the reagent away from direct sunlight in an amber glass bottle previously flushed with the nitrogen (4.2) and fitted with a ground glass stopper. 4.7 Sodium sulphate, 0,001 M standard reference solution. Weigh, to the nearest0,0001 g,0,1420 g of anhy
25、drous sodium sulphate, previously dried at110 C and cooled in a desiccator. Introduce into a 1000 ml one-mark volumetric flask, dissolve in water, dilute to the mark and mix. 1ml of this solution corresponds to96g of SO 4 . 4.8 Mercury (II) nitrate,0,05M standard volumetric solution (=0,1N). Dissolv
26、e10,85 0,01g of mercury (II) oxide (HgO) in10ml of nitric acid solution, approximately1,40g/ml, about68% (m/m) solution, dilute to 1000 ml with water and mix. NOTEThe strength of the solution thus prepared is sufficiently exact for the small quantities of sulphur compounds to be determined and stand
27、ardization is therefore unnecessary. In most laboratories, however, a precisely0,1N standard volumetric solution, commonly used for the mercurimetric determination of chlorides, will be available. 4.9 Mercury (II) nitrate,0,001M standard volumetric solution (=0,002N). Dilute20,00ml of the standard v
28、olumetric mercury(II) nitrate solution (4.8) to the mark in a1000 ml one-mark volumetric flask. Prepare this solution at the time of use. 4.10 Dithizone,0,5g/l solution in the acetone (4.1). 5 Apparatus Ordinary laboratory apparatus and 5.1 Microburette, capacity5ml, graduated in0,01ml (G). 5.2 Appa
29、ratus for reduction and distillation of which all the components are fitted together with ground glass joints. A typical apparatus is shown inFigure 1 and comprises: 5.2.1 Wash bottles (A and B), Drechsel type, capacity50ml. 5.2.2 Conical flasks (C), capacity100ml. 5.2.3 Reflux condenser (D).BS6075-
30、8:1981 2 BSI 10-1999 5.2.4 Absorption vessel (E), internal diameter25mm and height100mm. 5.2.5 Dropping funnel (F), capacity50ml. 5.2.6 Stopcocks (1, 2, 3 and 4). 5.3 Apparatus for preparation of the reduction solution (4.6). A typical apparatus is shown inFigure 2, and comprises: 5.3.1 Flask, three
31、-necked (J), capacity500ml. 5.3.2 Reflux condenser (K). 5.3.3 Nitrogen supply tube (L). 6 Procedure 6.1 Test portion Weigh, to the nearest0,01g, a mass of the test sample (seeISO3195), solid or liquid, not exceeding5or10g respectively, into a dried conical flask (C). Fit with a stopper. 6.2 Check te
32、st The purpose of this test is to check the gas-tightness and functioning of the apparatus (reduction of sulphur compounds and quantitative recovery of the hydrogen sulphide liberated). Transfer in turn: to the wash bottle (A),25ml of the potassium permanganate and mercury (II) chloride solution(4.4
33、); to the wash bottle (B),25ml of the pyrogallol solution (4.5); to the absorption vessel (E),5ml of the sodium hydroxide solution (4.3),5ml of the acetone (4.1) and0,1ml of the dithizone solution (4.10); to a dried conical flask (C),2,00ml of the standard reference sodium sulphate solution(4.7) and
34、 a few glass beads; to the dropping funnel (F),50ml of the reducing solution (4.6); to the microburette (G) the standard volumetric mercury (II) nitrate solution (4.9). Assemble the apparatus taking care to smear the ground joints with a silicone grease and to tighten them with suitable spring-clips
35、 in order to ensure perfect gas-tightness. Pass the nitrogen (4.2) through stopcocks (2) and (4), at a speed of about2bubbles per second. After5min, run the mercury (II) nitrate solution (4.9), drop by drop, into the absorption vessel (E) until the indicator changes from yellow to red. Open stopcock
36、s (1) and (3) to allow the reducing solution (4.6) to run into the conical flask (C), leaving a few millimetres of liquid in the dropping funnel (F), then close the two stopcocks. Start the condenser (D) and, while continuing the flow of nitrogen, boil the solution gently in the conical flask (C) fo
37、r at least30min. The presence of hydrogen sulphide is shown by a colour change of the indicator from red to yellow. Stop the boiling and, while maintaining the flow of nitrogen, titrate the sulphide in the absorption vessel (E) with the standard volumetric mercury (II) nitrate solution (4.9) contain
38、ed in the microburette(G) until 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 (4.9) used for the titration is between1,90and2,10ml, after subtraction of the blank test result (6
39、.3). Otherwise check the apparatus for leaks. 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 (4.7). 6.4 Determination Carry out the determination under the same cond
40、itions as the check test (6.2), using the test portion (6.1) instead of the2,00ml of the standard reference sodium sulphate solution (4.7). 7 Expression of results The content of sulphur compounds, expressed as milligrams of sulphate (SO 4 ) per kilogram, is given, by the formula where V 0is the vol
41、ume, in millilitres, of the standard volumetric mercury (II) nitrate solution (4.9) used for the blank test; V 1is the volume, in millilitres, of the standard volumetric mercury (II) nitrate solution (4.9) used for the determination; m is the mass, in grams, of the test portion (6.1); 96 is the mass
42、, in micrograms, of SO 4corresponding to1ml of the standard volumetric mercury (II) nitrate solution (4.9).BS6075-8:1981 BSI 10-1999 3 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
43、unusual features noted during the determination; d) any operation not included in this International Standard or in the International Standard to which reference is made, or regarded as optional.BS6075-8:1981 4 BSI 10-1999 Figure 1 Typical apparatus for the determination of sulphur compoundsBS6075-8
44、:1981 BSI 10-1999 5 Figure 2 Typical apparatus for the preparation of the reducing solutionBS6075-8:1981 6 BSI 10-1999 Annex ISO publications relating to sodium hydroxide for industrial use ISO 979, Method of assay. ISO/R 980, Determination of the carbon dioxide content, expressed as sodium carbonat
45、e Gas-volumetric method. ISO 981, Determination of chloride content Mercurimetric method. ISO/R 982, Determination of sulphate content Barium sulphate gravimetric method. ISO 983, Determination of iron content 1,10-Phenanthroline photometric method. ISO 984, Determination of silica content Reduced s
46、ilicomolybdic complex photometric method. ISO/R 985, Determination of silica content Gravimetric method by precipitation of the quinoline-silicomolybdic complex. ISO/R 986, Determination of calcium EDTA complexometric method. ISO/R 987, Determination of water-insoluble matter. ISO 3195, Sampling Tes
47、t sample Preparation of the main solution for carrying out certain determinations. ISO 3196, Determination of carbon dioxide content Titrimetric method. ISO 3197, Determination of chlorides content Photometric method. ISO 3198, Determination of sulphur compounds Method by reduction and titrimetry. I
48、SO 3697, Determination of calcium and magnesium contents Flame atomic absorption spectrophotometric method.BS6075-8:1981 BSI 10-1999 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 p
49、revent pollution of waste water. It is recommended principally for waste solutions from titrations using 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 mercury polysulphides), the insoluble mercury salts are removed by decantation and filtr
