1、BRITISH STANDARD BS 6981:1988 Method for Determination of acid content of wool UDC 677.31.01:541.8:546.131:547.291:547.292:546.226-325:620.1BS6981:1988 This British Standard, having been prepared under the directionof the Textiles andClothing Standards Committee, was published underthe authority of
2、the BoardofBSI and comes into effect on 31August1988 BSI 11-1999 The following BSI references relate to the work on this standard: Committee reference TCM/26 Draft for comment87/38082 DC ISBN 0 580 16665 1 Committees responsible for this British Standard The preparation of this British Standard was
3、entrusted by the Textiles and Clothing Standards Committee (TCM/-) to Technical Committee TCM/26, upon which the following bodies were represented: British Carpet Manufacturers Association Ltd. Department of Trade and Industry (Laboratory of the Government Chemist) International Wool Secretariat Man
4、-made Fibres Producers Committee Ministry of Defence Textile Research Council Amendments issued since publication Amd. No. Date of issue CommentsBS6981:1988 BSI 11-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Test spe
5、cimens 1 6 Procedure 1 7 Expression of results 2 8 Test report 2 Publications referred to Inside back coverBS6981:1988 ii BSI 11-1999 Foreword This British Standard has been prepared under the direction of the Textiles and Clothing Standards Committee and is a revision of the Appendix in BS3568:1962
6、. This standard is published to coincide with publication of a revision of BS3568. This British Standard is technically equivalent to ISO3073:1975. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct
7、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 and 2, an inside back cover and a back cover. This standard has been updated (see copyright
8、 date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6981:1988 BSI 11-1999 1 1 Scope This British Standard describes a method for determination of the acid content of wool. This procedure is applicable to undyed wool in any form,
9、e.g.loose fibre, sliver, yarn or fabric. It is also applicable to dyed wool when the amount of dye extracted during the test does not interfere with the determination of the end-point of the titration. NOTEThe titles of the publications referred to in this standard are listed on the inside back cove
10、r. 2 Principle A known amount of a test specimen is immersed in a dilute solution of pyridine which extracts the acid from the wool. The amount of acid extracted is determined by titration with sodium hydroxide solution. 3 Reagents 3.1 Pyridine solution, 5g/L. Dissolve5g of pyridine in1L of water (3
11、.2). CAUTION. Pyridine has toxic properties and should be handled with care. 3.2 Water, complying with grade3 of BS3978. 3.3 Sodium hydroxide solution, c(NaOH), 0.1mol/L. 3.4 Phenolphthalein indicator solution, 5g/L ethanolic solution. Dissolve0.5g of phenolphthalein in95% (V/V) ethanol and dilute t
12、o100mL with ethanol. 4 Apparatus 4.1 Conical flasks, 250mL capacity, fitted with ground glass stoppers. 4.2 Conical flasks, 250mL capacity. 4.3 Pipettes, 50mL and100mL capacity, complying with BS1583. 4.4 Burette, 25mL capacity, complying with BS846. 4.5 Stoppered weighing bottles, for weighing the
13、test specimens. 4.6 Balance, accurate to 0.0002g. 4.7 Desiccator 4.8 Ventilated oven, for drying specimens at105 3 C. 4.9 Mechanical shaker (optional). 4.10 Glass beakers, 250mL capacity. 4.11 Glass wool 5 Test specimens Take a sample representative of the bulk and not less than10g, sufficient to pr
14、ovide wool (free of fat and vegetable matter) for the following test specimens: a) one test specimen weighing approximately1g for determining the dry mass (see6.1); b) two test specimens each weighing approximately2g for determining the acid content (see6.2). NOTE 1It is assumed that the sample will
15、 be commercially free from oil and fatty matter. If this is not the case, then the procedure described in6.1 of BS3568:1988 should be followed. NOTE 2Useful information on sampling is given in BS2545. 6 Procedure 6.1 Determination of dry mass Place the1g test specimen (see clause5) in a weighing bot
16、tle (4.5) and dry it in the ventilated oven (4.8) at105 3 C. Stopper the bottle, cool it in the desiccator (4.7) and weigh it. Repeat these drying, cooling and weighing operations until the results of two consecutive weighings do not differ from each other by more than0.0005g, i.e.the mass is virtua
17、lly constant. Remove the test specimen, weigh the weighing bottle and hence calculate the dry mass of the test specimen. 6.2 Determination of acid content Place the two2g test specimens (see clause5) in separate glass-stoppered conical flasks (4.1) and add100mL of pyridine solution (3.1) to each. St
18、opper each flask and shake them on the mechanical shaker (4.9) for1h. Alternatively, allow each flask to stand overnight after initial shaking to ensure wetting of the specimen. Decant the liquid from each flask into separate glass beakers (4.10), filtering it through a plug of glass wool (4.11) to
19、retain fibrous material. From each beaker, pipette50mL of the filtered liquid into separate conical flasks (4.2), add three drops of phenolphthalein indicator solution (3.4) to each flask and titrate each extract with the sodium hydroxide solution (3.3) until a faint pink colour persists after a gen
20、eral shaking by hand. NOTEA potentiometric end-point determination is also acceptable.BS6981:1988 2 BSI 11-1999 7 Expression of results The mass of acid, s, expressed as a percentage of the dry mass of the test specimen, is given by the equation: where Express the results to one decimal place. 8 Tes
21、t report The test report shall include the following information: a) the number and date of this British Standard, i.e. BS6981:1988; b) a description or reference of the sample tested; c) the type of acid for which the calculation has been made; d) the individual results and their mean, expressed as
22、 in clause7; e) any departure from the method described, e.g.owing to insufficient material being available. T is the concentration of the sodium hydroxide solution used for the titration (in mol/L); V is the volume of the sodium hydroxide solution used for the titration (in mL); k is a constant whi
23、ch has the following values 3.65 for calculating as hydrochloric acid 4.60 for calculating as formic acid 4.90 for calculating as sulphuric acid 6.00 for calculating as acetic acid; m 1 is the dry mass of the test specimen determined as described in6.1 (in g). s TV k m 1 - =BS6981:1988 BSI 11-1999 P
24、ublications referred to BS 846, Specification for burettes. BS 1583, Specification for one-mark pipettes. BS 2545, Methods of fibre sampling for testing. BS 3568, Method for determination of solubility of wool in alkali. BS 3978, Specification for water for laboratory use. ISO 3073, Wool Determinati
25、on of acid content 1) . 1) Referred to in the foreword only.BS 6981:1988 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international le
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