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1、BRITISH STANDARD BS 7164-27.2: 1990 ISO 1657:1986 Chemical tests for raw and vulcanized rubber Part 27: Methods for determination of iron content Section 27.2 Photometric method Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:31:06 GMT+00:00 2006, Uncontrolle
2、d Copy, (c) BSI BS 7164-27.2:1990 This British Standard, having been prepared under the direction of the Rubber Standards Policy Committee, was published under the authority of the Board of BSI and comes into effect on 31 July 1990 BSI 11-1999 The following BSI references relate to the work on this
3、standard: Committee reference RUM/37 Draft for comment 82/55911 DC ISBN 0 580 18771 3 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Rubber Standards Policy Committee (RUM/-) to Technical Committee RUM/37, upon which the following bodie
4、s were represented: Institute of Water and Environmental Management Laboratory of the Government Chemist Ministry of Defence Royal Society of Chemistry Rubber and Plastics Research Association Amendments issued since publication Amd. No.DateComments Licensed Copy: London South Bank University, Londo
5、n South Bank University, Fri Dec 08 14:31:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7164-27.2:1990 BSI 11-1999i Contents Page Committees responsibleInside front cover National forewordii 1Scope and field of application1 2References1 3Principle1 4Reagents1 5Apparatus1 6Sampling2 7Procedure2 8E
6、xpression of results3 9Test report3 Publications referred toInside back cover Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:31:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7164-27.2:1990 ii BSI 11-1999 National foreword This Section of BS 7164 has been
7、prepared under the direction of the Rubber Standards Policy Committee and is identical with ISO 1657:1986 “Rubber, raw and rubber latex Determination of iron content 1, 10-Phenanthroline photometric method”, published by the International Organization for Standardization (ISO). BS 7164 rationalizes
8、all the methods that deal with chemical analysis of raw, compounded and vulcanized rubber some of which have previously been published in BS 903, BS 1673 and BS 5923. Relevant Parts of those standards will be withdrawn or deleted by amendment, as appropriate, when superseded by Parts and Sections of
9、 BS 7164. This Section of BS 7164 supersedes method 2.8 of BS 1673-2:1967, which will be deleted by amendment. 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 Britis
10、h Standard does not of itself confer immunity from legal obligations. Cross-references International StandardCorresponding British Standard ISO 123:1985 BS 6057 Rubber latices Part 2:1987 Sampling (Identical) ISO 124:1985Section 3.2:1987 Determination of total solids content (Identical) ISO 247:1978
11、aBS 5923 Methods for chemical analysis of rubber Part 1:1980 Determination of ash (Identical) ISO 1795:1974 ISO 1796:1982 BS 6315:1982 Methods for sampling and sample preparation of raw rubber (Technically equivalent) ISO 4793:1980BS 1752:1983 Specification for laboratory sintered or fritted filters
12、 including porosity grading (Identical) a This will be superseded by the revised edition of ISO 247 which is in preparation. It is envisaged that BS 7164-5, which will supersede BS 5923-1, will be identical to the revised edition of ISO 247. Summary of pages This document comprises a front cover, an
13、 inside front cover, pages i and ii, 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 inside front cover. Licensed Copy: London South Bank University
14、, London South Bank University, Fri Dec 08 14:31:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7164-27.2:1990 BSI 11-19991 1 Scope and field of application This International Standard specifies a 1,10-phenanthroline photometric method for the determination of 5 to 1 000 mg/kg of iron in uncompoun
15、ded natural rubber, uncompounded synthetic rubbers which do not contain chlorine, and in the corresponding uncompounded latices. 2 References ISO 123, Rubber latex Sampling. ISO 124, Rubber latices Determination of total solids content. ISO 247, Rubber Ash content Determination. ISO 1795, Raw rubber
16、 in bales Sampling. ISO 1796, Raw rubber Sample preparation. ISO 4793, Laboratory sintered (fritted) filters Porosity grading, classification and designation. 3 Principle Ashing of the raw rubber or the dried latex solids in a crucible. Extraction of the ash with hydrochloric acid and making up of t
17、he solution to standard volume. After adjustment of the pH by the addition of buffer solution, treatment of an aliquot part of the solution with hydroxylammonium chloride to reduce any iron(III) present to iron(II) and 1,10-phenanthroline with which the iron(II) forms an orange-red complex. Photomet
18、ric measurement of the absorbance of this solution, which is proportional to the concentration of iron. NOTEThe method used is closely similar to that given in ISO 6685, Chemical products for industrial use General method for determination of iron content 1,10-Phenanthroline spectrophotometric metho
19、d. 4 Reagents All reagents shall be of recognized high purity analytical quality suitable for use in trace metal analysis. Distilled water or water of equivalent purity shall be used whenever water is specified. 4.1 Hydrochloric acid, A 1,19 g/cm31). 4.2 1,10-Phenanthroline, solution. Dissolve 0,5 g
20、 of 1,10-phenanthroline monohydrate in hot water and, after cooling, provided that this does not cause precipitation, dilute the solution to 500 cm3. Store the solution away from the light and use only colourless solutions. 4.3 Hydroxylammonium chloride, solution. Dissolve 10 g of hydroxylammonium c
21、hloride in 100 cm3 of water. 4.4 Buffer solution Dissolve 164 g of anhydrous sodium acetate in approximately 250 cm3 of water and to the solution add 28,5 cm3 of glacial acetic acid, A 1,05 g/cm3. Dilute this mixture to 500 cm3 and filter immediately before use if it is cloudy. If this buffer soluti
22、on gives highly coloured reference solutions in the preparation of the calibration curve, an alternative buffer solution may be prepared by dissolving 80 g of sodium hydroxide or 106 g of anhydrous sodium carbonate in 200 cm3 of water, adding 142,5 cm3 of glacial acetic acid, A 1,05 g/cm3, and dilut
23、ing the solution to 500 cm3. 4.5 Iron, standard solution corresponding to 0,1 g of Fe per cubic decimetre. Dissolve 0,702 g, weighed to the nearest 0,000 5 g, of ammonium iron(II) sulfate hexahydrate (NH4)2Fe(SO4)2.6H2O in water in a 1 000 cm3 one-mark volumetric flask. Add 3 cm3 of concentrated hyd
24、rochloric acid, A 1,19 g/cm3, and dilute to the mark with water. This solution will generally remain stable for at least 1 month. 1 cm3 of this standard solution contains 0,1 mg of Fe. 4.6 Iron, standard solution for calibration corresponding to 0,01 g of Fe per cubic decimetre. Pipette 10 cm3 of th
25、e standard iron solution (4.5) into a 100 cm3 one-mark volumetric flask and dilute to the mark with water. 1 cm3 of this standard solution contains 0,01 mg of Fe. This solution shall be freshly prepared from the stock solution (4.5) at the time of use. 5 Apparatus Ordinary laboratory apparatus and 5
26、.1 Colorimeter or spectrophotometer, capable of measuring absorbance at approximately 510 nm, with matched 5 cm cells. 5.2 Silica or porcelain crucible, nominal capacity 50 to 80 cm3. 5.3 Muffle furnace, capable of maintaining a temperature of 525 25 C. 1) The term millilitre (ml) is commonly used a
27、s a special name for the cubic centimetre (cm3), in accordance with a decision of the Twelfth Confrence Gnrale des Poids et Mesures. The term millilitre is acceptable, in general, for references in International Standards to capacities of volumetric glassware and to liquid volumes. Licensed Copy: Lo
28、ndon South Bank University, London South Bank University, Fri Dec 08 14:31:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7164-27.2:1990 2 BSI 11-1999 5.4 Heat-resistant board, iron-free, approximately 100 mm square and 6 mm thick, with a hole in the centre, or silica triangle. The hole in the hea
29、t-resistant board or the size of the silica triangle shall be such that approximately two-thirds of the crucible projects below the board. 5.5 One-mark volumetric flasks, of capacity 50 cm3. 5.6 Graduated precision pipettes or burettes 5.7 Sintered glass crucible, of porosity P 40 or P 100 (see ISO
30、4793). 6 Sampling For raw rubber, carry out the sampling in accordance with ISO 1795. For latex, carry out the sampling in accordance with one of the methods specified in ISO 123. 7 Procedure 7.1 Preparation of homogenized test piece For the determination of iron in raw rubber, prepare a homogenized
31、 sheet in accordance with ISO 1796. For the determination of iron in latex, prepare a homogeneous sheet dried to constant mass, as specified in ISO 124, using a portion of thoroughly mixed latex containing at least 10 g of total solids. At all stages of sample preparation, take care to avoid contami
32、nation with iron, particularly from rusty knives, scissors, mills and other equipment unless chromed. 7.2 Preparation of calibration curve 7.2.1 Preparation of standard colorimetric solutions To a series of 50 cm3 one-mark volumetric flasks (5.5), add portions of the standard iron solution (4.6) ran
33、ging from 0 to 20 cm3 (for example 0; 0,5; 5; 10; 15; 20 cm3). These portions contain 0 to 200 4g of iron. 7.2.2 Colour development Add to each of the flasks in 7.2.1, 1 cm3 of the concentrated hydrochloric acid (4.1), 10 cm3 of the buffer solution (4.4), 1 cm3 of the hydroxylammonium chloride solut
34、ion (4.3) and 10 cm3 of the 1,10-phenanthroline solution (4.2). Dilute the solutions with water to the mark and mix thoroughly. Allow to stand at room temperature for 15 min. 7.2.3 Photometric measurements Measure the absorbance of the solutions using the colorimeter or spectrophotometer (5.1) at th
35、e absorption maximum (about 510 nm) using the matched 5 cm cells. Correct the reading by subtracting the absorbance of the solution containing no added iron. If the absorbance is measured on a double-beam instrument, place the cell containing the blank solution in the reference beam and measure the
36、absorbance of each standard matching solution against that of the solution containing no added iron. 7.2.4 Plotting the graph Plot the reading thus obtained for each solution of 7.2.1 against the appropriate concentration of iron to give the calibration curve, which shall be checked periodically acc
37、ording to local conditions and the type of instrument used. 7.3 Determination WARNING All precautions and safeguards required for the carrying out of trace metals analysis must be observed. 7.3.1 Preparation of test solution Cut into small pieces, each weighing approximately 0,1 g, a 10 g test porti
38、on of the homogenized test piece (7.1), prepared from the raw rubber or the dried latex. Transfer to the unetched crucible (5.2) and weigh to the nearest 0,01 g. Support the crucible in the hole cut in the heat-resistant board (5.4). Heat gently with a small2) gas flame until a dry carbonaceous resi
39、due remains and then transfer the crucible to the muffle furnace (5.3), maintained at a temperature of 550 25 C. Alternatively, wrap the weighed sample in a piece of ashless filter paper about 150 mm in diameter and transfer to the crucible. Place the crucible and its contents in the furnace at 550
40、25 C and close the furnace door. WARNING The furnace door must not be opened during the first hour because of the risk of igniting flammable gases. When all the carbon has been oxidized, remove the crucible and allow to cool. 2) Overheating may cause loss of iron when silica crucibles are used. Lice
41、nsed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:31:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7164-27.2:1990 BSI 11-19993 Add 5 cm3 of the hydrochloric acid (4.1) and 5 cm3 of water to the crucible and digest the mixture on a steam bath for 30 to 60 min. If
42、 the solution has a deep yellow colour, indicating the presence of much iron, add a further 5 cm3 of the hydrochloric acid and digest for a further 30 min. Filter the solution through a sintered glass crucible (5.7), transfer the filtrate to a 50 cm3 one-mark volumetric flask (5.5) and, after coolin
43、g, dilute to the mark. 7.3.2 Colour development Transfer an aliquot part of the test solution (7.3.1) containing not more than 2 cm3 of hydrochloric acid (4.1), or 400 4g of iron to a 50 cm3 one-mark volumetric flask. Add 10 cm3 of the buffer solution (4.4), then 1 cm3 of the hydroxylammonium chlori
44、de solution (4.3) and 10 cm3 of the 1,10-phenanthroline solution (4.2). Dilute the solution with water to the mark and mix thoroughly. Allow to stand at room temperature for 15 min. 7.3.3 Blank test In parallel with the determination and following the same procedure, carry out a blank determination
45、using a similar filter paper and crucible and using the same quantities of all the reagents as used for the determination. 7.3.4 Photometric measurements Carry out the photometric measurements on the test solution (7.3.1), and on the blank test solution (7.3.3) after colour development, measuring th
46、e absorbance of the solution at the wavelength used for preparing the calibration curve. Correct the reading for the test solution by subtracting the value for the absorbance of the blank solutions. If the absorbance is measured on a double-beam instrument, place the cell containing the blank soluti
47、on in the reference beam and measure the absorbance of the test solution against the blank solution. 8 Expression of results By means of the calibration curve, determine the concentration of iron corresponding to the corrected reading and from this calculate the iron content of the test portion. Exp
48、ress the result as parts per million (ppm) of iron (Fe) calculated by mass. 9 Test report The test report shall include the following particulars: a) reference to this International Standard; b) identification of the test sample; c) the results and the method of expression used; d) any unusual featu
49、res noted during the determination; e) any operation not included in this International Standard or in the International Standards to which reference is made, or regarded as optional. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:31:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI 4 blank Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:31:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7164-27.2:1990 BSI 11-1999 Publications referred to See national