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1、BRITISH STANDARD BS 6068-2.39: 1991 Incorporating Amendment No. 1 (Renumbers BS 6068-2.39:1991, ISO 9280:1990 as BS 6068-2.39:1991) Water quality Part 2: Physical, chemical and biochemical methods Section 2.39: Method for the determination of sulfate using barium chloride and gravimetry ICS 13.060.5
2、0 ? Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 04:16:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.39:1991 This British Standard, having been prepared under the direction of the Environment and Pollution Standards Policy Committee was published under the authority of the Standa
3、rds Board and comes into effect on 28 February 1991 BSI 10 February 2006 The following BSI references relate to the work on this British Standard: Committee reference EPC/44 Draft for comment 88/50951 DC ISBN 0580 19362 4 Committees responsible for this British Standard The preparation of this Briti
4、sh Standard was entrusted by the Environment and Pollution Standards Policy Committee (EPC/-) to Technical Committee EPC/44, upon which the following bodies were represented: Association of Consulting Scientists British Association for Chemical Specialities British Gas plc Chemical Industries Associ
5、ation Department of the Environment for Northern Ireland Department of the Environment (Water Directorate) Department of Trade and Industry (Laboratory of the Government Chemist) Electricity Supply Industry in England and Wales Industrial Water Society Institute of Petroleum Institution of Gas Engin
6、eers Institution of Water and Environmental Management National Rivers Authority Royal Institute of Public Health and Hygiene Royal Society of Chemistry Scottish Association of Directors of Water and Sewerage Services Soap and Detergent Industry Association Water Companies Association Water Research
7、 Centre Water Services Association of England and Wales Amendments issued since publication Amd. No.DateComments 16182February 2006 Renumbers BS 6068-2.39:1991, ISO 9280:1990 as BS 6068-2.39 and converts dual numbered standard to purely British Standard. Makes corrections to Clause 1, and to 4.3, 7.
8、1 and 9.1, see foreword. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 04:16:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.39:1991 BSI 10 February 2006 i Contents Page Committees responsibleInside front cover Forewordii 1Scope 1 2Principle 1 3Reagents 1 4Apparatus 2 5Sampling and
9、sample preparation 2 6Procedure 2 7Expression of results 3 8Interferences 4 9Special cases 5 10Notes on procedure 5 11Test report 5 Table 1 Conversion factors for other units of concentration (c) 4 Table 2 Repeatability and reproducibility standard deviations 4 Table 3 Tolerance to other ions 4 Lice
10、nsed Copy: sheffieldun sheffieldun, na, Tue Dec 05 04:16:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.39:1991 ii BSI 10 February 2006 Foreword This section of BS 6068, has been prepared under the direction of the Environment and Pollution Standards Policy Committee. This section of BS 606
11、8 is identical with ISO 9280:1990, and was originally published as a dual numbered standard. ISO 9280:1990 has now been withdrawn. This section of BS 6068 has therefore been amended to make it purely a British Standard. The original British Standard number (BS 6068-2.39) has been retained. The text
12、remains identical to ISO 9280:1990; however, the following textual errors which were identified in the original ISO text have now been corrected. a) In Clause 1, paragraph 2, first sentence, “10 mg/l” changed to “25 mg/l”. b) In 4.3, “at least” changed to “to an accuracy of ”. c) In 7.1, in the equa
13、tion and in the text below, “0.411 6” changed to read “411.6”. d) In 7.1, meaning of 411.6 changed to read: “is one thousand times the gravimetric factor ” e) In 9.1, paragraph 3, second sentence changed to: “Then allow to cool slightly, add 10 ml 1 ml of water, transfer quantitatively to a 500 ml b
14、eaker and proceed as described in 6.2.1, paragraph 1, beginning with “and add 2 drops of methyl orange .”.” NOTE The tests described in this section of BS 6068 should only be carried out in laboratories with suitable facilities and by suitably qualified persons with an appropriate level of chemical
15、expertise. Standard chemical procedures should be followed throughout. BS 6068 is being published in a series of parts subdivided into sections that will generally correspond to particular international standards. Sections are being, or will be, published in Parts 1 to 7, which together with Part 0,
16、 are listed below. Part 0: Introduction; Part 1: Glossary; Part 2: Physical, chemical and biochemical methods; Part 3: Radiological methods; Part 4: Microbiological methods; Part 5: Biological methods; Part 6: Sampling; Part 7: Precision and accuracy. This publication does not purport to include all
17、 the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. sulfate barium sulfate - Summary of pages This document comprises a front cover, an inside front cover, pages i an
18、d ii, pages 1 to 5 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 04:16:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.39:1991 BSI 10 February 2006 1 1 Scope This secti
19、on of BS 6068 specifies a gravimetric method for the determination of sulfate in water. The method is applicable to the analysis of all types of water, including sea water and most industrial effluents. For information on potentially interfering substances, see Clause 8. A sulfate concentration (exp
20、ressed as SO42) in the range of 25 mg/l to 5 000 mg/l can be determined using the specified test portion (6.1). It is possible to determine higher concentrations after dilution of the laboratory sample. The lower limit of detection (with nine degrees of freedom) is SO42 = 10 mg/1 2 Principle Acidifi
21、cation of the sample with hydrochloric acid followed by boiling with barium chloride solution for at least 20 min to promote coagulation of the precipitate of barium sulfate. Filtration through a tared sintered-glass crucible, washing the precipitate free from chloride, drying at 105 C and reweighin
22、g when cool. The increase in mass of the crucible is due to the barium sulfate precipitate formed by reaction of barium with sulfate ions in the sample. 3 Reagents Use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 3.1 Hydrochloric acid, c(HCl) =
23、 6 mol/l. With care, mix 500 ml 10 ml of concentrated hydrochloric acid (HCl) = 1.18 g/ml with water and dilute to 1 litre in a measuring cylinder. Store in a glass or polyethylene bottle. The solution is stable indefinitely. 3.2 Barium chloride, dihydrate solution, 100 g/l. WARNING. Barium chloride
24、 is poisonous and harmful if swallowed. Dissolve 100 g 1 g of barium chloride dihydrate (BaCl2.2H2O) in about 800 ml of water, warming the mixture to aid dissolution. Cool the solution and dilute to 1 litre with water in a measuring cylinder. Store in a glass or polyethylene bottle. The solution is
25、stable indefinitely. 3.3 Sodium hydroxide solution, c(NaOH) = 5 mol/l. WARNING. Sodium hydroxide solution is hazardous on contact with skin and eyes. Dissolve 20.0 g of sodium hydroxide in 100.0 ml of water, whilst stirring. Store in a polyethylene bottle. 3.4 Methyl orange, indicator solution, abou
26、t 1 g/l. Dissolve 100 mg of methyl orange in about 50 ml of water, warming the mixture to aid dissolution. Cool the solution and dilute to 100 ml with water in a measuring cylinder. Store in a glass or polyethylene bottle. The solution is stable indefinitely. 3.5 Silver nitrate solution, about 0.1 m
27、ol/l. Dissolve 17 g 1 g of silver nitrate, AgNO3, in about 800 ml of water and dilute to 1 litre in a measuring cylinder. Store in an amber glass bottle. The solution is stable indefinitely if protected from light. 3.6 Ethanol, C2H5OH, or rectified spirit (95 % ethanol, 5 % methanol). 3.7 Sodium chl
28、oride solution, 100 g/1. Dissolve 10.0 g 0.1 g of sodium chloride, NaCl, in about 100 ml of water. Store in a glass or polyethylene bottle. 3.8 Sodium carbonate, Na2CO3, anhydrous. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 04:16:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.39
29、:1991 2 BSI 10 February 2006 4 Apparatus 4.1 Sintered-glass crucibles, of capacity about 30 ml, porosity value of 4. 4.2 Buchner flask, equipped with safety guard for vacuum filtration. 4.3 Analytical balance, capable of weighing to an accuracy of 0.000 2 g. 4.4 Platinum evaporating dish, of capacit
30、y 250 ml. 5 Sampling and sample preparation 5.1 Sampling Collect samples in glass or polyethylene bottles and analyse on the day of collection or store at 2 C to 5 C for not more than one week. Fill the sample bottles completely to exclude air and thus eliminate the risk of oxidation of samples cont
31、aining sulfide or sulfite. NOTE Samples low in organic matter may be kept for longer periods, but tests should be carried out to ensure that samples are sufficiently stable. 5.2 Preparation of test sample For the determination of sulfate in solution allow any suspended solids to settle prior to with
32、drawing the test portion (6.1). Alternatively, filter the laboratory sample through a fine porosity, ashless filter paper in order to prepare a test sample. 6 Procedure 6.1 Test portion The test portion volume shall be between 10 ml and 200 ml and shall contain not more than 50 mg of sulfate ions. U
33、sing a pipette, withdraw the test portion from the settled test sample (see 5.2). NOTE For shaken test samples containing large amounts of suspended solids it may be necessary to measure the test portion in a measuring cylinder, but with a likely consequent decrease in the accuracy and precision of
34、the method. 6.2 Pretreatment 6.2.1 Measure the test portion (6.1) into a 500 ml beaker and add 2 drops of methyl orange indicator (3.4). Neutralize the test portion with hydrochloric acid (3.1) or sodium hydroxide solution (3.3) depending on the initial pH. Add 2 ml 0.2 ml of hydrochloric acid and t
35、hen, if necessary, add water to bring the total volume in the beaker to 200 ml 20 ml. Boil the contents of the beaker for at least 5 min. If the solution is clear after boiling, proceed to 6.3. If insoluble material is present, filter the hot mixture through a fine porosity, ashless filter paper and
36、 wash the filter paper with a small amount of hot water, combining the washing with the filtrate. Transfer the solution quantitatively to a 500 ml beaker and proceed to 6.3. 6.2.2 If it is suspected that the insoluble material retained by the filter paper contains insoluble sulfate and it is desired
37、 to include this in the final result, retain the filter paper and carry out the procedure given in 9.2. 6.2.3 If silica is present in the test portion at concentrations likely to interfere (see Clause 8), follow the pretreatment method given in 9.1. 6.2.4 If organic substances are present in the tes
38、t portion at concentrations likely to interfere (see Clause 8), follow the pretreatment method given in 9.1. 6.3 Precipitation Boil the solution produced at the end of the pretreatment (6.2) and slowly add, using a pipette, 10 ml 1 ml of hot (about 80 C) barium chloride solution (3.2). Heat the solu
39、tion for at least 1 h, cover and allow to cool and stand overnight at 50 C 10 C. NOTE Slow addition of the hot barium chloride reduces the possibility of coprecipitation. Subsequent heating aids coagulation of the precipitate and renders it more crystalline, reducing coprecipitation even further. Li
40、censed Copy: sheffieldun sheffieldun, na, Tue Dec 05 04:16:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6068-2.39:1991 BSI 10 February 2006 3 6.4 Filtration 6.4.1 Procedure Dry a sintered-glass crucible (4.1) by heating it to 105 C for 1 h and let it cool in a desiccator. Accurately weigh the cr
41、ucible (to the nearest 0.000 2 g) and then fit it on a Buchner flask (4.2). Filter the precipitate using gentle suction. Use a rubber-tipped glass rod to dislodge any precipitate remaining in the beaker and rinse with cold water into the crucible. Wash the precipitate in the crucible with chloride-f
42、ree cold water. 6.4.2 Test for chloride in the washings Collect about 5 ml of the filtrate from 6.4.1 in a small beaker containing about 5 ml of silver nitrate solution (3.5). To ascertain whether the washings and hence the barium sulfate precipitate are free from chloride, observe the mixture and c
43、heck that no turbidity is formed. Otherwise continue washing. NOTE It is also important to check that no chloride remains on the rim of the underside of the crucible. 6.5 Drying and weighing Remove the crucible and dry it at 105 C 2 C for about 1 h. Transfer the crucible to a desiccator and weigh it
44、 when it has cooled to room temperature so that the mass is accurately known. Return the crucible to the drying oven for a further 10 min and repeat the cooling and weighing. Provided that the second mass differs by not more than 0.000 2 g from the first, record the second mass. Otherwise repeat the
45、 drying, cooling and weighing until two successive masses do not differ by more than 0.000 2 g. NOTE Shorter drying periods may be obtained if the precipitate is washed with three 5 ml portions of ethanol (3.6). 6.6 Blank test For a check of crucibles to be used in the test follow a procedure identi
46、cal to that given in 6.3, 6.4 and 6.5, but using 200 ml 20 ml of water. Subtract the crucible mass recorded before filtration as in 6.4 from that recorded after filtration as in 6.5 to obtain the blank mass in grams. NOTE If filtration is necessary during sample pretreatment (6.2), the portion of wa
47、ter used in the blank test shall first be filtered as described in the second paragraph of 6.2.1, unless previous tests have demonstrated that no contribution to the blank arises from filtration. 7 Expression of results 7.1 Calculation Calculate the mass of barium sulfate in the test sample, m, in g
48、rams, from the following equation: where Calculate the sulfate concentration, in milligrams per litre as SO42 from the following equation: where m = m2 m1 m0(1) m0is the blank mass, in grams, calculated in 6.6; m1is the crucible mass, in grams, recorded in 6.4; m2is the crucible mass, in grams, reco
49、rded in 6.5. (2) mis the mass of barium sulfate precipitate, in grams; Vis the test portion volume, in millilitres (see 6.1); 411.6is one thousand times the gravimetric factor . m1 000411.6 V - sulfate barium sulfate - Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 04:16:31 GMT+00:00 2006, Uncontrolled Copy, (c) BSI