1、BRITISH STANDARD BS 5666-5: 1986 Methods of analysis of Wood preservatives and treated timber Part 5: Determination of zinc naphthenate in preservative solutions and treated timber NOTEIt is essential that this Part is read in conjunction with Part 1 “General considerations and sampling and preparat
2、ion of materials for analysis.” UDC 674.048:620.1BS5666-5:1986 This British Standard, having been prepared under the directionof the Wood PreservationStandards Committee, was published underthe authority of the BoardofBSI and comes into effecton 28February1986 BSI 11-1999 The following BSI reference
3、s relate to the work on this standard: Committee reference WPC/11 Draft for comment 84/55183 DC ISBN 0 580 15022 4 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Wood Preservation Standards Committee (WPC/-) to Technical Committee WPC/1
4、1, upon which the following bodies were represented: Association of Consulting Scientists British Drier Manufacturers Association British Wood Preserving Association Department of the Environment (Building Research Establishment, Princes Risborough Laboratory) Ministry of Defence A British Standard
5、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 obligations. Summary of pages This document comprises a front cover, an i
6、nside front cover, pagesi andii, pages1to6, 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. Amendments issued since publication Amd. No. Date
7、of issue CommentsBS5666-5:1986 BSI 11-1999 i Contents Page Committees responsible Inside front cover 1 Scope and field of application 1 2 MethodI. Atomic absorption spectrophotometric method 1 3 MethodII. Colorimetric method 3 4 Test report 6 Publications referred to Inside back coverii blankBS5666-
8、5:1986 BSI 11-1999 1 1 Scope and field of application This Part of BS5666 describes procedures for the determination of zinc naphthenate, expressed as zinc, in preservative solutions and in treated timber. Two methods are described: an atomic absorption spectrophotometric method and a colorimetric m
9、ethod. Both methods have been found suitable for the determination of zinc naphthenate in the presence of tributyltin oxide, pentachlorophenol, o-phenylphenol, monochloronaphthalene, polychloronaphthalene, gamma-HCH (gamma-BHC) 1) , dieldrin 1) , copper naphthenate, water-repellent waxes and resins.
10、 The procedures described have been primarily designed for the analysis of preservative formulations complying with BS5707-1. For samples of other compositions it may be necessary to make adjustments in the quantities taken for analysis. The timber sample for analysis may be in the form of sawdust,
11、wood flour or thin sections. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. CAUTION. Attention is drawn to the general safety precautions mentioned in clause4 ofBS5666-1:1978. 2 Method I. Atomic absorption spectrophotometric method 2.1 Principle
12、The zinc in the zinc naphthenate present is extracted quantitatively from preservative solutions or treated timber with hydrochloric acid solution. The resulting zinc solution is analysed using an atomic absorption spectrophotometer. The determination is carried out in the presence of excess potassi
13、um ions because the presence of sodium or potassium ions enhances the zinc absorbance signal. 2.2 Reagents Except where otherwise specified, all reagents shall be of recognized analytical grade and water complying with BS3978 shall be used throughout. 2.2.1 White spirit, complying with BS245. 2.2.2
14、Hydrochloric acid solution, c(HCl)=5mol/L approximately. Dilute500mL of concentrated hydrochloric acid( 20 =1.18g/mL) to1L with water. 2.2.3 Hydrochloric acid solution, c(HCl)=1mol/L approximately. Dilute100mL of concentrated hydrochloric acid ( 20 =1.18g/mL) to1L with water. 2.2.4 Hydrochloric acid
15、/potassium chloride solution. Dissolve4.8g of potassium chloride in100mL of water. Add this to100mL of concentrated hydrochloric acid( 20 =1.18g/mL) and dilute to1L with water. 2.2.5 Standard zinc solution. 1mLN 1004g of zinc. Dissolve0.100g of zinc metal in100mL of concentrated hydrochloric acid so
16、lution ( 20 =1.18g/mL). Transfer the solution to a1L one-mark standard volumetric flask (see2.3.1) and dilute to the mark with water. 2.3 Apparatus 2.3.1 Volumetric glassware, of classA quality in accordance withBS700-2 (typeII), BS846, BS1583 orBS1792, as appropriate. 2.3.2 Atomic absorption spectr
17、ophotometer, together with a suitable source of resonance radiation for zinc,e.g. a hollow cathode lamp. 2.4 Procedure 2.4.1 Instrument settings and operation. The instrument settings and operating conditions for the determination of zinc shall be as recommended by the instrument manufacturer. Zinc
18、is determined in an air/acetylene flame at a wavelength of213.9nm. 2.4.2 Preparation of calibration solutions, Into a series of100mL one-mark volumetric flasks, transfer0,0.50,1.00,2.00,3.00,4.00,5.00, and10.00mL of the standard zinc solution(2.2.5). Add20mL of the hydrochloric acid/potassium chlori
19、de solution(2.2.4) and dilute to the mark with the hydrochloric acid solution(2.2.3). These calibration solutions contain 0, 0.5, 1.0, 2.0, 3.0, 4.0,5.0,and10.04g/mL respectively of zinc. NOTEA usable calibration graph should be obtained over the range of04g/mL to54g/mL zinc. Above this value, the c
20、urve becomes progressively non-linear. It is recommended that this part of the graph should not be used for the determination, but it is useful for obtaining approximate values. 2.4.3 Analysis of preservative solutions 2.4.3.1 Preparation of test solution, Accurately weigh approximately1g (seenote)
21、of the preservative solution into a tared50mL one-mark volumetric flask. Dilute to the mark with the white spirit(2.2.1) and mix thoroughly. NOTEThis mass may be adjusted to obtain a zinc content within the range of the procedure if the preservative has not been formulated to comply with BS5707-1. 1
22、) SeeBS1831.BS5666-5:1986 2 BSI 11-1999 Pipette1mL of this solution into a50mL separating funnel, add approximately10mL of white spirit and swirl to mix. Extract successively with three20mL portions of the hydrochloric acid solution(2.2.3). For each extraction, shake vigorously for at least90s, allo
23、w to settle, and run off the aqueous layer into a100mL one-mark volumetric flask. Add20mL of the hydrochloric acid/potassium chloride solution(2.2.4) to the flask, dilute to the mark with the hydrochloric acid solution(2.2.3) and mix to provide the test solution. 2.4.3.2 Measurement. Using the opera
24、ting conditions suitable for the instrument used, aspirate successively an appropriate range of calibration solutions(see2.4.2), the test solution or solutions, and again the calibration solutions to check the stability of the instrument readings, and measure the absorbance of each solution. NOTEIf
25、a number of samples are to be analysed, it may be advisable to check the instrument stability by bracketing each test solution between appropriate calibration solutions. Plot a calibration curve of the concentration of zinc against absorbance for the range of calibration solutions. If the absorbance
26、 of the test solution is above the range for the calibration solutions, adjust the concentration of the test solution by diluting it with a mixture of20mL of the hydrochloric acid solution(2.2.4) and80mL of the hydrochloric acid solution(2.2.3) so that the absorbance falls within this range, and not
27、e the dilution factor. Then repeat the aspiration procedure with both calibration solutions and test solution to produce revised values. Determine the zinc content of the test solution by reference to the calibration graph and express the concentrations as micrograms of zinc per millilitre of the te
28、st solution. 2.4.4 Analysis of treated timber 2.4.4.1 Preparation of timber sample for analysis. Prepare the sample for analysis by converting the treated timber into a form suitable for extraction(i.e. shavings or sawdust) as described inBS5666-1. Divide the prepared sample into two portions, each
29、of about0.5g. On one portion determine the moisture content according to the procedure described in7.2 ofBS5666-1:1978. NOTEFor the purposes of this clause, in line2 of7.2 of BS5666-1:1978 the word “extraction” should be read as “preparation”. 2.4.4.2 Extraction and preparation of test solution, Acc
30、urately weigh about0.5g (seenote) of the prepared timber sample(2.4.4.1) into a tared50mL conical flask. NOTEFor treated timber it is difficult to recommend quantities to be taken for analysis because the predominant factor is the amount of preservative within the timber rather than the mass of the
31、wood itself. It may therefore be necessary to make some adjustments to the values quoted in this standard either in respect of the mass of treated timber sample taken for analysis or the level of dilution of the zinc solution resulting from the extraction. Add10mL of the hydrochloric acid solution (
32、2.2.2) and stand the flask in a water bath, controlled at55 C to60 C, for30min with occasional swirling. Remove the flask from the water bath, cool to room temperature and filter the contents of the flask through a filter paper 2)into a50mL one-mark volumetric flask. Wash the residue and the filter
33、paper thoroughly with water and add the washings to the volumetric flask. Dilute to the mark with water and mix. Pipette25mL of this solution into a100mL one-mark volumetric flask, add20mL of the hydrochloric acid/potassium chloride solution(2.2.4) and dilute to the mark with the hydrochloric acid s
34、olution(2.2.3). Mix thoroughly to give the test solution. 2.4.4.3 Measurement. Determine the zinc content of the test solution as described in2.4.3.2. 2.4.5 Calculations 2.4.5.1 Preservative solutions, The percentage by mass of zinc in the preservative is given by the formula: where 2) A Whatman No.
35、44 filter paper has been found to be suitable. C is the concentration of zinc in the test solution(2.4.3.1) as determined from the calibration graph (in4g/mL); m 1 is the mass of the preservative solution taken (ing); D is the dilution factor arising from the adjustment of the concentration of the t
36、est solution (no adjustment,D=1)(see2.4.3.2). CD 2m 1 -BS5666-5:1986 BSI 11-1999 3 2.4.5.2 Treated timber. The percentage by mass of zinc in the dry test sample is given by the formula: where 3 Method II. Colorimetric method 3.1 Principle The zinc in the zinc naphthenate present is extracted quantit
37、atively from preservative solutions or treated timber with a hydrochloric acid solution. The zinc content of the resulting solution is separated from other metals by a partitioning sequence between toluene and buffered aqueous systems. The zinc is then determined colorimetrically as the dithizone co
38、mplex. 3.2 Reagents All reagents shall be of recognized analytical grade and water complying with BS3978 shall be used throughout. 3.2.1 Toluene, complying with grade2 of BS805. 3.2.2 White spirit, complying with BS245. 3.2.3 Ammonia solution, concentrated ( 20 =0.880g/mL). 3.2.4 Sodium sulphate, an
39、hydrous and granular. 3.2.5 Acetic acid/sodium acetate solution. Dissolve27.2g of sodium acetate trihydrate in100mL of water, add12mL of glacial acetic acid and dilute to200mL with water. 3.2.6 Acetate buffer solution. Prepare this solution daily as required. Transfer50mL of the acetic acid/sodium a
40、cetate solution(3.2.5) and10mL of the sodium thiosulphate solution(3.2.16) to a100mL separating funnel and extract this mixture successively with5mL portions of the dithizone solution(3.2.10) until the green colour persists. Extract once more with5mL of the dithizone solution(3.2.10) and then with5m
41、L of the toluene(3.2.1). Discard the toluene extract and washings and store the extracted acetate buffer solution in a well-stoppered bottle. 3.2.7 Citric acid solution. Dissolve100g of citric acid in100mL of water and dilute to200mL with water. 3.2.8 Citrate buffer solution. Prepare this solution d
42、aily as required. Transfer20mL of the citric acid solution(3.2.7) to a100mL separating funnel. Using litmus paper as an indicator, neutralize this solution with the ammonia solution(3.2.3), add a further1.5mL of the ammonia solution and dilute to a total volume of30mL with water. Extract successivel
43、y with5mL portions of the dithizone solution(3.2.10) until the green colour persists. NOTEThe aqueous phase should be pale yellow. If it is not, add further ammonia solution drop by drop, shaking after each addition, until the aqueous phase becomes pale yellow. Extract once more with5mL of the dithi
44、zone solution(3.2.10) and then wash the aqueous phase with successive5mL portions of the toluene(3.2.1) until the aqueous phase is colourless. Discard the toluene extract and washings and store the extracted citrate buffer solution in a well-stoppered bottle. 3.2.9 Dithizone stock solution. Dissolve
45、0.1g of diphenylthiocarbazone (dithizone) in100mL of the toluene(3.2.1) and dilute to250mL with the toluene(3.2.1). Store this solution in a refrigerator. 3.2.10 Dilute dithizone solution. Prepare this solution daily as required. Extract100mL of the dithizone stock solution(3.2.9) with two successiv
46、e200mL portions of water each containing4mL of the ammonia solution(3.2.3) using a500mL separating funnel 3) . Discard the toluene layer. Transfer the combined aqueous extracts to a1L separating funnel, acidify with the hydrochloric acid solution(3.2.13) and extract the precipitated dithizone with40
47、0mL of the toluene(3.2.1). Wash the toluene extract with two successive200mL portions of water and filter the separated toluene solution through a dry filter “ashless” paper 4) . Keep the solution cool and away from direct light. 3.2.11 Hydrochloric acid solution, c(HCl)=5mol/L approximately. Dilute
48、500mL of concentrated hydrochloric acid solution( 20 =1.18g/mL) to1L with water. 3.2.12 Hydrochloric acid solution, c(HCl)=1mol/L approximately. Dilute100mL of concentrated hydrochloric acid solution( =1.18g/mL) to1L with water. 3.2.13 Hydrochloric acid solution, c(HCl) = 0.1 mol/L approximately. Di
49、lute50mL of the hydrochloric acid solution(3.2.12) to500mL with water. C is the concentration of zinc in the test solution(2.4.4.2) as determined from the calibration graph (in4g/mL); m 2 is the oven dry equivalent mass of the test portion of the prepared timber sample, i.e.the mass of the test portion corrected for the moisture content (see2.4.4.1) (ing); D is the dilution factor arising from the adjustment of the concentration of the test solution (no adjustment,D=1) (see2.4.3.2). CD 50m 2 - 3) It may be necessary to filter the combined a
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