1、BRITISH STANDARD BS ISO 14849:1999 Plastics Phenol-formaldehyde mouldings Determination of free ammonia and ammonium compounds Indophenol method ICS 83.080.10BSISO14849:1999 This British Standard, having been prepared under the directionof the Sector Committeefor Materials and Chemicals, was publish
2、ed underthe authority of the Standards Committee and comesinto effect on 15November1999 BSI 03-2000 ISBN 0 580 35232 3 National foreword This British Standard reproduces verbatim ISO 14849:1999 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Te
3、chnical Committee PRI/21, Testing of plastics, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related internat
4、ional and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Sta
5、ndards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible
6、 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, theISO title page, pages ii to iv, pages 1 to 7 and a back cover. This standard
7、 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. Amendments issued since publication Amd. No. Date CommentsBSISO14849:1999 BSI 03-2000 i Contents Page National foreword Inside front cover Forewor
8、d iii Text of ISO14849 1ii blankBSISO14849:1999 ii BSI 03-2000 Contents Page Foreword iii 1 Scope 1 2 Normative references 1 3 Terms and definitions 1 4 Principle 2 5 Reagents 2 6 Apparatus 3 7 Preparation of test sample 3 8 Procedure 4 9 Expression of results 7 10 Precision 7 11 Test report 7 Figur
9、e 1 Example of distillation apparatus (simple distillation) 5 Figure 2 Example of steam-distillation apparatus 6 Table 1 Interlaboratory trial data 7BSISO14849:1999 BSI 03-2000 iii Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodie
10、s (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations,
11、 governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO
12、/IEC Directives, Part 3. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75% of the member bodies casting a vote. International Standard ISO 14849 was prepared by
13、Technical Committee ISO/TC 61, Plastics, Subcommittee SC 12, Thermosetting materials.iv blankBSISO14849:1999 BSI 03-2000 1 1 Scope This International Standard specifies a colorimetric comparison method for the determination of the amount of ammonia and ammonium compounds in phenol-formaldehyde mould
14、ings. NOTEThis International Standard does not provide an absolute measure of the amount of ammonia present. The amount of ammonia in a moulded article is of importance when corrosion of metal inserts or contamination of foodstuffs in contact with the article has to be considered. 2 Normative refere
15、nces The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this
16、 International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently vali
17、d International Standards. ISO 565:1990, Test sieves Metal wire cloth, perforated metal plate and electroformed sheet Nominal sizes of openings. ISO 648:1977, Laboratory glassware One-mark pipettes. ISO 835-2:1981, Laboratory glassware Graduated pipettes Part 2: Pipettes for which no waiting time is
18、 specified. ISO 1042:1988, Laboratory glassware One-mark volumetric flasks. ISO 3696:1987, Water for analytical laboratory use Specification and test methods. ISO 4788:1980, Laboratory glassware Graduated measuring cylinders. ISO 4793:1980, Laboratory sintered (fritted) filters Porosity grading, cla
19、ssification and designation. ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method. 3 Terms and definitions For the purposes of this International Standard
20、, the following terms and definitions apply. 3.1 free ammonia ammonia that is present in the form of NH 3in phenol-formaldehyde mouldings 3.2 ammonium compound an ammonium salt, present in a phenol-formaldehyde moulding, that has been produced by the reaction of ammonia with acid NOTEIn this method,
21、 ammonium compounds are determined as NH 3 .BSISO14849:1999 2 BSI 03-2000 4 Principle The ammonia in a test portion of ground mouldings is extracted by heating with water. The extract is then distilled in alkaline conditions. The ammonia present in the distillate is determined by measuring the spect
22、rophotometric absorbance of the indophenol blue generated by the reaction with phenol in the presence of hypochlorite ions. The reactions are as follows: 5 Reagents During the analysis, use only ammonia-free reagents of recognized analytical grade, and only ammonia-free distilled water of grade 3 as
23、 defined in ISO 3696. 5.1 Potassium permanganate 5.2 Sodium hydroxide, 2% solution. 5.3 EDTA solution Dissolve 5 g of ethylenediaminetetraacetic acid disodium dihydrate in 100 ml of water. 5.4 Sodium phenolate solution Dissolve 20 g of sodium hydroxide in 100 ml of water. Then dissolve 25g of phenol
24、 in 55 ml of this NaOH solution. Allow to cool to room temperature and add 6 ml of acetone. Dilute the resulting solution to 200ml with water. Since the solution of sodium phenolate tends to absorb carbon dioxide from the atmosphere, prepare it immediately before use. 5.5 Sodium hypochlorite solutio
25、n, available-chlorine content 0,01 g/ml. Determine the concentration of available chlorine in a solution of sodium hypochlorite with an available-chlorine content between 0,05 g/ml and 0,12 g/ml and dilute it with water so that the chlorine content is adjusted to approximately 0,01 g/ml. Since sodiu
26、m hypochlorite is prone to decomposition, prepare the solution immediately before use. Determine the exact concentration of the sodium hypochlorite solution as follows: Introduce 10 ml of the solution into a 200 ml volumetric flask and make up to 200 ml with water. Transfer 10 ml of this solution to
27、 a conical flask. Dilute with 90 ml of water, making the total volume100ml. Add 1 g to 2 g of potassium iodide and 6 ml of acetic acid (1+1). Seal the flask and thoroughly mix the contents by shaking. Place the flask containing the mixture in a dark place for about 5 min and then titrate the content
28、s with0,05 mol/l sodium thiosulfate solution (5.7). When the yellow solution becomes light-coloured, add about 2 ml of starch solution (5.8) and continue the titration until the blue colour of starch iodide disappears. Separately, carry out a blank test on 10 ml of water and correct the titration vo
29、lume accordingly.BSISO14849:1999 BSI 03-2000 3 Calculate the available-chlorine content N, in grams per millilitre, of the sodium hypochlorite solution from the equation where V 1 is the volume, in millilitres, of sodium hypochlorite solution transferred to the conical flask (i.e.10ml); V 2 is the v
30、olume, in millilitres, of 0,05 mol/l sodium thiosulfate solution required for the titration; f is a correction factor for the case when the concentration of the sodium thiosulfate solution is not exactly 0,05 mol/l; 0,001773is the mass, in grams, of chlorine corresponding to 1 ml of 0,05 mol/l sodiu
31、m thiosulfate solution. 5.6 Standard ammonia solution, c(NH 3 ) = 0,01mg/ml. Put 3,141 g 0,001 g of ammonium chloride, which has been dried to constant mass at 105 C (but in any case for a minimum of 2 h) into a 1000 ml volumetric flask and make up to the mark with water. Pipette10ml of this solutio
32、n into a second 1 000 ml volumetric flask and again make up to the mark with water. 5.7 Sodium thiosulfate solution, c(Na 2 S 2 O 3 ) = 0,05 mol/l. Dissolve 7,906 g of sodium thiosulfate in water in a 1000 ml volumetric flask, and make up to the mark with water. 5.8 Starch solution Take 1 g of starc
33、h, and dissolve in 100 ml of water. 6 Apparatus Ordinary laboratory apparatus, plus the following: 6.1 Means for reducing the mouldings to powder, for example drill, file, ball mill, mortar and pestle. 6.2 Sieve, with nominal openings of 250 4m as specified in ISO 565. 6.3 Analytical balances, one a
34、ccurate to 0,01 g, the other accurate to 0,001 g. 6.4 Flask, capacity 100 ml, with ground-glass stopper. 6.5 Graduated measuring cylinders, capacity 100 ml and 50 ml, with ground-glass stoppers, both conforming to ISO 4788. 6.6 Glass filter, porosity P160 as specified in ISO 4793, or high-speed filt
35、er paper. 6.7 One-mark pipette, class A as specified in ISO 648, capacity 10 ml, and graduated pipette, class A as specified in ISO 835-2, capacity 10 ml. 6.8 One-mark volumetric flasks, class A as specified in ISO 1042, capacities 50 ml, 200 ml and 1000 ml. 6.9 Conical flask, capacity 300 ml, with
36、ground-glass stopper. 6.10 Distillation apparatus, as shown in Figure 1 or Figure 2. 6.11 Photometer or spectrophotometer. 7 Preparation of test sample Reduce a representative sample of the moulding to powder by filing, milling, grinding or drilling, taking care that no undue heating of the material
37、 occurs. Sieve the powder, using the sieve described in subclause6.2. The test sample shall consist of the portion that passes through the sieve. Keep the test sample in a tightly stoppered flask, and start the extraction procedure described in clause 8 within 1 h of preparing it.BSISO14849:1999 4 B
38、SI 03-2000 8 Procedure 8.1 Extraction Weigh out 5 g 0,1 g of the sieved material (see clause 7) to the nearest 0,01 g. Place this test portion in a100 ml flask (6.4). Using a 100 ml measuring cylinder (see 6.5), add 50 ml of water, heated to not less than90 C, and immediately stopper the flask with
39、its ground-glass stopper. Shake the flask so that the powder is thoroughly wetted. Allow to cool, and leave at room temperature for 1h, with occasional shaking. Then filter the contents of the flask, without suction, through a glass filter or filter paper (6.6). 8.2 Distillation Using a pipette (6.7
40、), transfer 10 ml of the filtered extract to a 250 ml distillation flask (see Figure 1 or Figure 2). Add 1g of potassium permanganate (5.1) and 10 ml of 2% sodium hydroxide solution (5.2). Gently distill the mixture using the apparatus shown in Figure 1 or Figure 2. Collect the first 15 ml of distil
41、late in a 50 ml measuring cylinder (see 6.5). Make up to 25 ml with water. NOTEIf the purple colour of potassium permanganate disappears, add further potassium permanganate so as to keep the purplecolour. 8.3 Measurement To the 25 ml of solution obtained in 8.2, add 1ml of EDTA solution (5.3) and 10
42、 ml of sodium phenolate solution (5.4), and mix by shaking the stoppered measuring cylinder. Then add 5 ml of sodium hypochlorite solution (5.5) and make up to 50 ml with water. Stopper and mix by shaking. Allow to stand for 30 min, keeping the temperature of the solution at 23 C 2 C. Transfer part
43、of this solution to a 10 mm absorption cell, and measure the absorbance at 630 nm wavelength. Also carry out a blank test at 630 nm wavelength using water, and correct the measured absorbance of the test solution. From the calibration curve prepared as described in subclause 8.4, read off the mass o
44、f ammonia, in milligrams, in the test solution. If the mass of ammonia in the test solution lies outside the range covered by the calibration curve, dilute the filtrate to bring it within the range of the calibration curve. The depth of colour of the solution is temperature-dependent, and it is ther
45、efore essential that the temperature of the solution is kept at 23 C 2 C. The solutions used in the preparation of the calibration curve shall also be kept at this temperature. 8.4 Preparation of the calibration curve Using between 0,5 ml and 10 ml of standard ammonia solution (5.6) and a series of
46、50 ml volumetric flasks (see 6.8), prepare at least three solutions with different ammonia concentrations. Then, using the procedure described in subclause 8.3, measure the absorbances and plot a graph showing the relationship between absorbance and the mass of ammonia in the solution. Ensure that t
47、he absorbance of the test solution lies within the range covered by the calibration solutions. NOTEInterfering materials: Iron(II) and copper(II) Concentrations of less than 0,15 mg/l do not interfere with the measurement. For concentrations of up to 1 mg/l, the interference is removed by the additi
48、on of the EDTA. Fatty-acid amines No interference. Aromatic amines, e.g.aniline Cause interference when coloured material is generated by oxidation by hypochlorite. p-Aminophenol Generates indophenol blue by reaction with phenol in alkaline solution and therefore interferes. Hydroquinone No interfer
49、ence. Hydroxylamine Interference may be removed by oxidation with a quantitative addition of a 30% aqueous solution of hydrogen peroxide.BSISO14849:1999 BSI 03-2000 5 Figure 1 Example of distillation apparatus (simple distillation)BSISO14849:1999 6 BSI 03-2000 Figure 2 Example of steam-distillation apparatusBSISO14849:1999 BSI 03-2000 7 9 Expression of results Calculate the content of free ammonia and ammonium compounds A, expressed as a percentage by mass of ammonia (NH 3 ), in the sample using the equa
