1、BRITISH STANDARD BS 6646:1985 Incorporating Amendment No. 1 Method for Determination of ash of textiles UDC 677.074.014.27:543.822BS6646:1985 This British Standard, having been prepared under the directionof the Textiles and Clothing Standards Committee,was published underthe authority of the Boardo
2、fBSI and comes intoeffecton 29November1985 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference TCM/26 Draft for comment 84/39980 DC ISBN 0 580 14664 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted
3、 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 Manchester Te
4、sting House Man-made Fibres Producers Committee Ministry of Defence Textile Research Council Amendments issued since publication Amd. No. Date of issue Comments 5720 July 1988 Indicated by a sideline in the marginBS6646:1985 BSI 12-1999 i Contents Page Committees responsible Inside front cover Forew
5、ord ii 1 Scope 1 2 Principle 1 3 Apparatus 1 4 Procedure 1 5 Expression of results 2 6 Test report 2 Publication referred to Inside back coverBS6646:1985 ii BSI 12-1999 Foreword This British Standard has been prepared under the direction of the Textiles and Clothing Standards Committee. This method
6、was included in the1974 edition of BS Handbook No. 11 “Methods of test for textiles” as a recommended method. However, due to the wide usage of this method it had been decided that it be revised and published as a British Standard. The major change from the method in Handbook No. 11 is that the spec
7、imens are carbonized at a low temperature before incineration at700 C. At the time of publication of this British Standard, no corresponding International Standard exists. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are respon
8、sible 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 front cover, pages i and ii, pages1 and 2, an inside back cover and a back cover. This standard has bee
9、n updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.BS6646:1985 BSI 12-1999 1 1 Scope This British Standard describes a method for determination of ash of textiles. NOTEThe title of the publication referred
10、to in this standard is given on the inside back cover. 2 Principle An amount of the textile of known mass, previously dried at105 3 C, is incinerated and the mass of the residual ash is determined. 3 Apparatus 3.1 Drying oven, controlled at105 3 C. 3.2 Silica or porcelain crucibles, with loose-fitti
11、ng lids, of about40mL capacity. 3.3 Desiccator (vacuum type), containing a suitable desiccant, e.g. silica gel. 3.4 Furnace, controlled at approximately700 C, situated in a fume cupboard or under a fume hood. 3.5 Balance, having an accuracy of0.1mg. 3.6 Bunsen burner 3.7 Tripod 3.8 Triangle, made of
12、 pipe clay. 3.9 Stoppered weighing bottle 4 Procedure WARNING NOTE. It is important that fumes do not enter the laboratory, causing potential build up of toxic volatile metals such as mercury, cadmium or antimony. Also acrylic fibres on ashing at700 C produce the highly toxic gas hydrogen cyanide. D
13、etermine the tared mass of a crucible with its lid, as follows. Prepare a crucible and lid (3.2) by heating in a furnace (3.4) at the requisite test temperature for at least2h. Allow to cool in the desiccator (3.3) for at least1h and determine the combined mass of the crucible and lid. Repeat the pr
14、ocess of heating, cooling and weighing until the results of two consecutive weighings of the combined mass do not differ from each other by more than0.5mg, i.e. the mass is virtually constant. Meanwhile, weigh approximately2.5g of the textile, cut into5mm squares in the case of fabrics, or10mm lengt
15、hs in the case of fibres and yarns, in a weighing bottle (3.9) that has been similarly tared, along with its stopper, in the drying oven (3.1). Dry in the oven for12h to18h (conveniently, overnight) together with the tared stopper (seenote6). Then, transfer the stoppered weighing bottle and its cont
16、ents to the desiccator and allow to cool to ambient temperature for at least1h. After weighing, derive the oven-dry mass of the specimen by simple subtraction of the tare figure. Transfer the specimen quantitatively to the tared crucible, replace the lid and pre-ash the contents of the crucible, sup
17、ported by the pipe-clay triangle(3.8) and the tripod (3.7) above a low bunsen burner flame (3.6). Continue heating until the specimen is fully carbonized, taking care that ignition does not occur, as this may give rise to erratic results from indeterminate losses. Place the covered crucible and cont
18、ents at the entrance of the furnace operating at the requisite test temperature for a few minutes until all volatile matter has been evolved. Then, remove the crucible lid, put it to one side and close the door of the furnace. Allow incineration to proceed to completion (seenote4). Allow the crucibl
19、e and contents to cool slightly, and replace the lid. Transfer the crucible, contents and lid to the desiccator and allow to cool for at least1h. Determine the mass of the crucible, lid and residue. Repeat the process of incineration, cooling and weighing until the results of two consecutive weighin
20、gs do not differ from each other by more than0.5mg, i.e. the mass is virtually constant. NOTE 1Ashing is complete when no carbonaceous matter remains in the crucible. NOTE 2The mass of material used for the test is governed by the anticipated ash, e.g. for grey cottons a5g sample is generally used;
21、for a well-scoured or bleached cotton material a10g sample is needed to give an amount of ash that can be determined with reasonable accuracy. NOTE 3For many purposes the initial drying of the sample may be neglected and an average figure assumed for the moisture content of the particular fibre. NOT
22、E 4Certain metals can be lost under these conditions of heating. Mercury is lost readily, and zinc is lost at temperatures above450 C. Temperatures in excess of the general ashing temperature may occur locally in large samples and the general ashing temperature in such cases may have to be considera
23、bly reduced to avoid loss of certain metals. Lead is also lost under the specified conditions of heating unless sulphate ion is present. NOTE 5Silica and porcelain crucibles become etched during heating and cooling cycles over a prolonged period. Consequently, crucibles should be renewed fairly freq
24、uently. NOTE 6The tared stopper should be kept apart from the weighing bottle throughout this part of the operation.BS6646:1985 2 BSI 12-1999 5 Expression of results Express the ash as a percentage by mass; given by the following expression, where m 0 is the mass of the oven-dry specimen (in g); m 1
25、 is the mass of the tared crucible and lid (ing); m 2 is the mass of the crucible, lid and ash (in g). 6 Test report The test report shall include the following: a) the number and date of this British Standard; b) the description of the sample tested; c) the result obtained, expressed as in clause5;
26、 d) the details of any deviation from the procedure. m 2 m 1 m 0 -100 BS6646:1985 BSI 12-1999 Publication referred to Handbook No. 11, Methods of test for textiles 1) . 1) Referred to in foreword only.BS 6646:1985 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the ind
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