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1、BRITISH STANDARD BS 5923-2: 1980 Methods for Chemical analysis of rubber Part 2: EDTA titrimetric method for determination of zinc content of rubber products UDC 678.4:543.244.6:546.47 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:14 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5923-
2、2:1980 This British Standard, having been prepared under the direction of the Rubber Standards Committee, was published under the authority of the Executive Board and comes into effect on 30 June 1980 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference R
3、UC/37 Draft for comment 78/55298 DC ISBN 0 580 11459 7 Cooperating organizations The Rubber Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: British Associ
4、ation of Synthetic Rubber Manufacturers* British Rubber Manufacturers Association* Department of Industry (Chemicals and Textiles) Medical Sterile Products Association Ministry of Defence* Plastics and Rubber Institute Rubber and Plastics Research Association of Great Britain* Rubber Growers Associa
5、tion Society of Motor Manufacturers and Traders Limited The Malaysian Rubber Producers Research Association* The organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: C
6、hemical Society, Analytical Division Electric Cable Makers Confederation Institution of Water Engineers and Scientists National College of Rubber Technology Individual expert Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:5
7、9:14 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5923-2:1980 BSI 12-1999i Contents Page Cooperating organizationsInside front cover Forewordii 1Scope and field of application1 2References1 3Principle1 4Reagents1 5Apparatus2 6Procedure2 7Expression of results2 8Test report3 Publications referred to
8、Inside back cover Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:14 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5923-2:1980 ii BSI 12-1999 Foreword This Part of BS 5923 has been prepared under the direction of the Rubber Standards Committee. In the past, methods for the chemical anal
9、ysis of different types of rubber were published, as appropriate, in the “B series” of BS 903 “Methods of testing vulcanized rubber” and in BS 1673 “Methods for testing raw rubber and unvulcanized compounded rubber”. However, in many cases the methods for the various types of material are very simil
10、ar. In the work of Technical Committee 45, Rubber and rubber products, of the International Organization for Standardization (ISO), this has led to the preparation of International Standards for methods for the chemical analysis of rubber of general applicability; in order to facilitate the adoption
11、 of these as British Standards and to simplify the general presentation of methods for the chemical analysis of rubber, it has been decided to publish this new British Standard. As further Parts of BS 5923 are published, they will replace any corresponding methods in BS 903 and BS 1673, so that the
12、BS 903 “B series” and the appropriate parts of BS 1673 will eventually be withdrawn completely. This Part supersedes section 4 of BS 903-B13 “Determination of ash and zinc oxide”; the remaining sections of BS 903-B13 are superseded by BS 5923-1. This Part is based on ISO 2454:1976, with the inclusio
13、n of some technical and editorial changes in the text. The major changes are listed below and are indicated by a vertical line in the margin. The changes in clauses in 4, 6.2 and 6.3 have been proposed by the United Kingdom as amendments to the ISO text. The method described in BS 903-B13 involved t
14、itration with EDTA solution but the procedure described in this revision differs substantially. Clause reference Textual change 6.1In this British Standard, a reference to BS 5923-1 has been substituted for the reference to ISO 247:1978. BS 5923-1 is identical with ISO 247:1978. 4In ISO 2454:1976 so
15、me of the reagents are listed in a different order as follows: 4.11 EDTA (disodium salt) 4.12 Zinc chloride 4.13 Dithizone indicator 4.13The note in this British Standard is not included in ISO 2454:1976. 6.2The instructions in the first paragraph have been extended. In ISO 2454:1976, the end of the
16、 first paragraph reads: “. . . . . . add 2 ml of the sulphuric acid (4.4) and ash in the muffle furnace (5.1), maintained at 550 25 C. In the second sentence of the second paragraph, the words “in a fume cupboard” have been added after “Evaporate the hydrofluoric acid”. In the fourth sentence of the
17、 second paragraph, ISO 2454:1976 refers, incorrectly, to the evaporation of “hydrochloric” acid. 6.3In ISO 2454:1976, the second sentence of the third paragraph begins, incorrectly, with the word “Acidity”. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:14 GMT+00:00 2006, Uncontrolled
18、Copy, (c) BSI BS 5923-2:1980 BSI 12-1999iii 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 does not of itself confer immunity from legal obligation
19、s. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 4, 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 ins
20、ide front cover. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:14 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:14 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5923-2:1980 BSI 12-19991 1 Scope and field of application
21、 This British Standard specifies an EDTA titrimetric method for the determination of the zinc content of all rubber products. Lead, magnesium, iron, titanium, antimony, silica, and silicates in the ash do not interfere. The method is not applicable, however, if cobalt is present. 2 References The ti
22、tles of the publications referred to in this standard are listed on inside back cover. 3 Principle Incineration of a test portion and dissolution of the ash in hydrochloric acid. Extraction of silica by treatment with hydrofluoric and sulphuric acids. Addition of aluminium chloride and aluminium flu
23、oride to precipitate calcium and magnesium as hexafluoroaluminates. Fluoride complexes iron, titanium and excess aluminium (interference from large amounts of iron is further reduced by addition of 2,4-pentanedione). Titration of the zinc with an EDTA (disodium salt) standard volumetric solution in
24、the presence of dithizone as indicator. 4 Reagents During the analysis, use only reagents of recognized analytical grade, and only distilled water or water of equivalent purity. All recognized health and safety precautions must be observed in the handling of chemicals listed and in performing the an
25、alysis. 4.1 Acetone 4.2 2,4-Pentanedione, 10 % (V/V) solution in the acetone (4.1). 4.3 Hydrochloric acid ( 1.18 g/ml). 4.4 Sulphuric acid ( 1.84 g/ml). 4.5 Hydrofluoric acid, 48 % (m/m) solution. 4.6 Ammonium hydroxide solution ( 0.01 g/ml). 4.7 Buffer solution. Dissolve 60 g of acetic acid (CH3COO
26、H) and 77 g of ammonium acetate (CH3COONH4) in water and dilute to 1 000 ml1) with water. 4.8 Aluminium chloride, 0.1M solution. Dissolve 2.42 g of aluminium chloride hexahydrate (AlCl3.6H2O) in water and dilute to 100 ml with water. 4.9 Magnesium chloride, 0.1M solution. Dissolve 2.03 g of magnesiu
27、m chloride hexahydrate (MgCl2.6H2O) in water and dilute to 100 ml with water. 4.10 Ammonium fluoride, 3M solution. Dissolve 55.5 g of ammonium fluoride (NH4F) in water and dilute to 500 ml with water. Store in a polyethylene or wax-coated bottle. 4.11 Zinc chloride, standard solution. Calcine zinc o
28、xide in a porcelain crucible for 2 h in the furnace (5.1), maintained at 550 25 C, and cool in a desiccator. Dissolve about 1.0 g of the dried reagent, weighed to the nearest 0.000 1 g, in 50 ml of water and 20 ml of the hydrochloric acid (4.3). Transfer to a 1 000 ml volumetric flask and dilute to
29、the mark with water. 4.12 Dithizone indicator. Dissolve 0.01 g of dithizone (phenylazo)thioformic acid, 2-phenylhydrazide in 10 ml of the acetone (4.1). Prepare a fresh solution every 48 h. 4.13 (Ethylenedinitrilo)tetraacetic acid disodium salt, dihydrate (ECTA disodium salt), 0.01M standard volumet
30、ric solution. NOTEThis solution should be prepared and standardized as described in 4.13.1 to 4.13.3. Standard solutions purchased from reagent suppliers may contain mercury salts, added as preservative, which will interfere with the dithizone indicator and possibly mask the end-point. 4.13.1 Prepar
31、ation. Dissolve 3.72 g of EDTA (disodium salt) in water and dilute to 1 000 ml with water. 4.13.2 Standardization. Pipette 25 ml of the standard zinc chloride solution (4.11) into a 250 ml conical flask. Add 5 ml of the hydrochloric acid (4.3) and proceed according to 6.3 beginning with “add 2 ml of
32、 the aluminium chloride solution”. Carry out the titration as described in 6.4, using the 50 ml burette (5.3). 4.13.3 Standardization factor. The standardization factor, T, of the EDTA (disodium salt) solution, expressed as grams of zinc oxide (ZnO) per millilitre, is given by the formula where m1 i
33、s the mass, in grams, of dried zinc oxide used in the preparation of the standard zinc chloride solution (4.11); V1 is the volume, in millilitres, of EDTA (disodium salt) solution used in the titration of the standard zinc chloride solution (4.11). 4.14 Universal indicator paper 1) The term millilit
34、re (ml) is commonly used for the cubic centimetre (cm3), particularly to denote the capacity of laboratory glassware. Apparatus with either type of marking is satisfactory to use with this British Standard. T m1 40 V1 - -= Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:14 GMT+00:00 200
35、6, Uncontrolled Copy, (c) BSI BS 5923-2:1980 2 BSI 12-1999 5 Apparatus Ordinary laboratory apparatus and 5.1 Muffle furnace, capable of being controlled at 550 25 C. 5.2 Burette, of capacity 10 ml, graduated in 0.02 ml divisions. 5.3 Burette, of capacity 50 ml, graduated in 0.1 ml divisions. 5.4 Pla
36、tinum crucibles, of capacity 50 ml. 6 Procedure 6.1 Weigh, to the nearest 0.000 1 g, approximately 1 g of the sample. Place this test portion in one of the platinum crucibles (5.4) and reduce to ash according to method C specified in BS 5923-1. Cool the crucible and add approximately 50 ml of the hy
37、drochloric acid (4.3). Transfer the contents of the crucible to a 250 ml beaker with approximately 50 ml of water. Break up any large cakes of ash with a glass stirring rod. If any insoluble residue is present after cooling, proceed in accordance with 6.2. If no insoluble material is present, procee
38、d in accordance with 6.3. 6.2 Filter the residue through an ashless filter paper. Retain the filtrate. Place the insoluble residue and the filter paper into a second platinum crucible (5.4), add 2 ml of the sulphuric acid (4.4) and then heat over a gas burner to volatilize the excess sulphuric acid.
39、 Transfer the crucible and its contents to the muffle furnace, maintained at 550 25 C, and heat until all the carbon is completely oxidized and a clean ash is obtained. Moisten the residue with 5 to 10 drops of the sulphuric acid (4.4) and 5 ml of the hydrofluoric acid solution (4.5). Evaporate the
40、hydrofluoric acid in a fume cupboard and stop heating as soon as the evolution of white fumes indicates sulphuric acid decomposition. When cool, add an additional 5 to 10 drops of the sulphuric acid and 5 ml of the hydrofluoric acid solution. Repeat the evaporation of the hydrofluoric acid and add 1
41、 ml of the sulphuric acid and 5 ml of the hydrofluoric acid solution to the wet residue. Evaporate the hydrofluoric acid and stop heating as soon as white fumes appear. Pour the contents of the crucible carefully into the retained filtrate, wash the crucible with distilled water and add the washings
42、 to the filtrate. Proceed according to 6.3. 6.3 If necessary, evaporate the solution or filtrate to a volume of approximately 50 ml. Transfer the cooled solution to a 100 ml volumetric flask and make up to the mark with distilled water. Select an aliquot portion from the following table according to
43、 the expected zinc content and transfer to a 250 ml conical flask. If necessary, dilute the aliquot portion to 25 ml, add 2 ml of the aluminium chloride solution (4.8), 5 ml of the magnesium chloride solution (4.9), and 10 ml of the ammonium fluoride solution (4.10). Add ammonium hydroxide solution
44、(4.6) until alkaline to the universal indicator paper (4.14). Acidify with approximately 1 ml of the sulphuric acid (4.4). Bring the solution to the boil, and then cool to room temperature. Add ammonium hydroxide solution (4.6) until just alkaline. Then add an additional 0.5 ml. Add 10 ml of the buf
45、fer solution (4.7), 60 ml of the acetone (4.1), 5 ml of the 2,4-pentanedione solution (4.2) and 5 drops of the dithizone indicator solution (4.12). Cool the solution in an ice bath. 6.4 Titrate with the EDTA (disodium salt) standard volumetric solution (4.13), using the appropriate burette indicated
46、 in the table. The end-point is reached at a yellow-green colour, which does not change on the addition of a further drop of the EDTA (disodium salt) standard volumetric solution. 7 Expression of results The zinc content of the test portion, expressed as a percentage by mass of zinc oxide (ZnO), is
47、given by the formula where T is the standardization factor as calculated in 4.13.3; V2 is the volume, in millilitres, of the EDTA (disodium salt) standard volumetric solution (4.13) used in the titration of the aliquot portion of the test solution; V3 is the volume, in millilitres, of the aliquot po
48、rtion; m2 is the mass, in grams, of the test portion. ZnO expectedAliquot portion Capacity of burette to be used % (m/m) 0 to 3 3 to 8 more than 8 ml 25 10 10 ml 10 (5.2) 10 (5.2) 50 (5.3) TV2100100 V3m2 - - Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:14 GMT+00:00 2006, Uncontrolled
49、 Copy, (c) BSI BS 5923-2:1980 BSI 12-19993 8 Test report The test report shall include the following particulars: a) a reference to this British Standard; b) the results and the method of expression used; c) any unusual features noted during the determination; d) any operation not included in this British Standard or in the British Standard to which reference is made, or regarded as optional. Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:59:14 GMT+00:00 2006, Uncontrolled Copy, (c