1、BRITISH STANDARD CONFIRMED JUNE1993 BS6337-1: 1983 ISO6228:1980 General methods of chemical analysis Part1: Method for determination of traces of sulphur compounds by reduction and titrimetry ISO title: Chemical products for industrial use General method for determination of traces of sulphur compou
2、nds, as sulphate, by reduction and titrimetry UDC543.242.8.064:546.22BS6337-1:1983 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, waspublished under the authorityof the Board ofBSIandcomesinto effecton 31January1983 BSI11-1999 The following BSI r
3、eferences relate to the work on this standard: Committee reference CIC/- Draft for comment79/56529 DC ISBN 0 580 13150 5 Cooperating organizations The Chemicals Standards Committee, under whose direction this BritishStandard was prepared, consists of representatives from the following: Association o
4、f Fatty Acid Distillers British 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 Agricult
5、ure, Fisheries and Food Ministry 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 organizat
6、ions marked with an asterisk 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 CommentsBS6337-1:1
7、983 BSI 11-1999 i Contents Page 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 Methods for the mineralization of organic compounds for the de
8、termination of low contents of sulphur 6 Annex B Interferences 7 Annex C Removal of mercury from residual solutions 7 Figure 1 Typical apparatus for reduction and entrainment 4 Figure 2 Typical apparatus for the preparation of the reducing solution 5BS6337-1:1983 ii BSI 11-1999 National foreword Thi
9、s Part of BS6337 is the first of a series of general methods of chemical analysis prepared under the direction of the Chemical Standards Committee. Itisidentical with ISO6228:1982 “Chemical products for industrial use General method for determination of traces of sulphur compounds, as sulphate, by r
10、eduction and titrimetry”, published by the International Organization for Standardization (ISO). For some years, the UK has participated in the work of Subcommittee1 General methods, of Technical Committee47 Chemistry, of ISO. As international agreement is reached on the methods, it is proposed to p
11、ublish 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 differing to various degrees, that had been prepared by the ISO/TC47 sub-committees, etc., responsible for part
12、icular 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 intended to reduce such proliferation, as far as is possible. They assume that a suitable test solution
13、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 species and how to overcome them, and how the results should be expressed. It is hoped and expected that any
14、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 of this BritishStandard. Because a general method cannot take into account the properties of all the pro
15、ducts 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. Thecompiler of the product standard should indicate how the test portion is to be treated in order to obtain a test solution with the required charac
16、teristics. 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 interferences might be expected in a particular product and what action should be taken if they are present so
17、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 cases that the general method will be applicable to a particular material. Terminology and conventions. The
18、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 been used as a deci
19、mal 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. Some confusion may be caused by the us
20、e of inconsistent terminology in the 5th paragraph of the lefthand column on page3. In line2 “connection tube” and line4 “test tube” are used for items which in Figure 1 and elsewhere are respectively called the “connecting tube” and “receiver”.BS6337-1:1983 BSI 11-1999 iii A British Standard does n
21、ot 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 legal obligations. Summary of pages This document comprises a front cover, an inside
22、front cover, pagesi toiv, pages1to7 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 blankBS6337-1:1983 BSI 11-1999 1 1 Scope This International Standard specifie
23、s a general reduction and titrimetric method for the determination, as sulphate, of trace quantities of sulphur compounds in chemical products for industrial use. The International Standard relating to the chemical product to which the method is to be applied shall specify the method by which the te
24、st portion should be treated in order to convert the sulphur compounds to sulphate, if necessary, together with any modifications to the general procedure that may be needed. 2 Field of application The method is applicable to the determination of amounts of sulphate (SO) of between4,5 and4504g, eith
25、er in solution or, in some cases, directly in the test portion. The volume of solution taken for the determination shall not contain more than2ml of water; the test portion shall not contain more than the acceptable limits of interfering elements, as specified in the International Standard relating
26、to the chemical product to which the method is to be applied. The sulphate can be present as such in the product or can be produced by suitable pre-treatment of a sample containing other sulphur compounds to give a test solution. The precision that can be expected is5%. NOTEBy replacing the reducing
27、 solution by hydrochloric acid, it is possible to determine sulphides (but not polysulphides) in the presence of other sulphur compounds. 3 Principle Prior conversion of the sulphur compounds in a test portion to sulphate, if required, and reduction of the sulphate ions to hydrogen sulphide by a mix
28、ture of hydriodic and phosphinic (hypophosphorous) acids in the presence of hydrochloric acid. Entrainment of the hydrogen sulphide in a current of nitrogen and absorption in a solution of sodium hydroxide in aqueous acetone. Titration of the sulphide ions with standard volumetric mercury(II) acetat
29、e or nitrate solution in the presence of1,5-diphenyl-3-thiocarbazone (dithizone) asindicator. 4 Reagents During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 4.1 Acetone 4.2 Nitrogen, oxygen free. 4.3 Sodium hydroxide, 40g/l so
30、lution. 4.4 Reducing solution Place in a1000ml flask, fitted with three ground necks and a bulb reflux condenser (see, for example, Figure 2), in the following order and under a current of the nitrogen(4.2), 100ml of hydriodic acid solution, approximately1,71g/ml, about57%(m/m) solution; 25ml of pho
31、sphinic (hypophosphorous) acid (H 3 PO 2 ) solution, approximately1,21g/ml, about50% (m/m) solution; 100ml of hydrochloric acid solution, approximately1,19g/ml, about38% (m/m) solution. Fit the reflux condenser to the flask and, while bubbling a gentle current of the nitrogen(4.2) through the mixtur
32、e, boil under reflux for about4h. Cool to ambient temperature, maintaining the current of nitrogen. Store the reagent away from direct sunlight in a dark glass flask fitted with a ground glass stopper, and under a nitrogen atmosphere obtained by purging the flask initially with the nitrogen(4.2). Th
33、e solution is stable for several weeks. NOTEThis reagent should be prepared in a fume cupboard so as to remove liberated hydrogen chloride. 4.5 Sodium sulphate, standard reference solution, c(Na 2 SO 4 )=0,001mol/l. Weigh, to the nearest0,0001g,0,1420g of anhydrous sodium sulphate, previously dried
34、for2h at about110 C and allowed to cool in a desiccator. Dissolve in about100ml of water and transfer the solution quantitatively to a1000ml one-mark volumetric flask. Dilute to the mark and mix. 1ml of this standard solution contains964g ofSO. 4.6 Sodium sulphate, standard reference solution, c(Na
35、2 SO 4 )=0,0001mol/l. Transfer100,0ml of the standard reference sodium sulphate solution(4.5), to a1000ml one-mark volumetric flask, dilute to the mark and mix. 1ml of this standard solution contains9,64g ofSO. Prepare this solution at the time of use. 4.7 Mercury(II) acetate, standard volumetric so
36、lution, cHg(CH 3 COO) 2 =0,001mol/l. Weigh, to the nearest0,0001g0,3187g of mercury(II) acetate Hg(CH 3 COO) 2 . Dissolve in about100ml of water and transfer the solution quantitatively to a1000ml one-mark volumetric flask. Dilute to the mark and mix. 2 4 2 4 2 4BS6337-1:1983 2 BSI 11-1999 The follo
37、wing solution can be used as an alternative. 4.7.1 Mercury(II) nitrate, standard volumetric solution, cHg(NO 3 ) 2 =0,001mol/l. Weigh10,83 0,01g of mercury(II) oxide (HgO), place in a beaker of convenient capacity (forexample100ml) and dissolve in10ml of nitric acid solution, approximately1,40g/ml,
38、about68% (m/m) solution. Dilute the solution, transfer quantitatively to a1000ml one-mark volumetric flask, dilute to the mark and mix. NOTEThis solution may also be prepared by dissolution of a mass of17,13g of mercury(II) nitrate monohydrate Hg(NO 3 ) 2 H 2 O in water acidified with1ml of nitric a
39、cid solution, approximately1,40g/ml. Transfer20,00ml of this solution, to a1000ml one-mark volumetric flask, dilute to the mark andmix. Prepare the latter solution at the time of use. 4.8 Mercury(II) acetate, standard volumetric solution, cHg(CH 3 COO) 2 =0,0001mol/l. Transfer100,0ml of the mercury(
40、II) acetate solution(4.7), to a1000ml one-mark volumetric flask, dilute to the mark and mix. Prepare this solution at the time of use. The following solution can be used as an alternative. 4.8.1 Mercury(II) nitrate, standard volumetric solution, cHg(NO 3 ) 2 =0,000 1mol/l. Transfer100,0ml of the mer
41、cury(II) nitrate solution(4.7.1), to a1000ml one-mark volumetric flask, dilute to the mark and mix. Prepare this solution at the time of use. NOTEThe concentration of the solutions(4.7, 4.7.1, 4.8 and4.8.1) as prepared are sufficiently exact, taking into account the low levels of sulphate ions to be
42、 determined. Standardization is, therefore, not necessary. 4.9 1,5-Diphenyl-3-thiocarbazone (dithizone), 0,5g/l solution in the acetone(4.1). Discard the solution after2 weeks. 5 Apparatus Ordinary laboratory apparatus and 5.1 Apparatus for reduction and entrainment (of the type, for example, shown
43、in Figure 1), of which all the components are connected by means of ground glass joints, with the exception of the flexible joint. 5.2 Microburette, graduated in0,01ml. 6 Procedure WARNING Mercury compounds are toxic and must be handled with precaution. Store the residual solutions obtained from the
44、 titrations, and treat them as specified in Annex C, so as to avoid the pollution of waste water by the mercury. 6.1 Test portion and preparation of the test solution Weigh a mass of the test sample and prepare the test solution following the procedure specified in the International Standard relatin
45、g to the product to which the method is to be applied. The test solution shall meet the following requirements: a) It shall contain either in its total volume or in the aliquot portion taken for the determination not more than2ml of water and between4,5 and4504g of sulphate ions (SO). b) It shall be
46、 free from the interferences listed in Annex B or shall have been treated to eliminate their influence. NOTEIf the product is liquid or is a solid soluble in acids, of which the expected sulphate ions content of the test portion is between4,5 and4504g, the test portion shall be introduced directly i
47、nto the flask of the reduction apparatus(5.1). 6.2 Check test Check the gas-tightness and functioning of the apparatus (reduction of sulphur compounds and quantitative recovery of the hydrogen sulphide liberated) as follows. Introduce5ml of the sodium hydroxide solution(4.3),5ml of the acetone(4.1)
48、and0,1ml of the dithizone solution(4.9) into the test tube of the apparatus. Mix and add, drop by drop, the appropriate mercury(II) acetate or nitrate solution, as indicated in the table below, until the colour changes from yellow to pink. NOTEIf too small a volume of the0,0001mol/l titration soluti
49、on is required (in the order of1ml), reduce to1drop the addition of the dithizone solution so as to detect more easily the end-point of the reaction. Introduce2,00ml of the appropriate standard reference sodium sulphate solution(4.5 or4.6) into the clean and dry reduction flask(5.1). Expected SO content Standard volumetric mercury(II) acetate or nitrate solution Standard reference sodium sulphate solution g From4,5 to60 From45 to450 4.8 or4.8.1 4.7 or4.7.1 4.6 4.5 2 4 2 4BS6337-1:1983 BSI 11-1999 3 Assemble the apparatus
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