1、BRITISH STANDARD BS 6070-7: 1981 Methods of Sampling and test for sodium carbonate for industrial use Part 7: Determination of copper content NOTEIt is recommended that this Part be read in conjunction with the information in the “Generalintroduction” published separately as BS6070-0. UDC 661.833.62
2、2:546.33264:543.42.062:546.56BS6070-7:1981 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authority ofthe Executive Board and comesinto effect on 27February1981 BSI 12-1999 The following BSI reference relates to the work o
3、n this standard: Committee reference CIC/22 ISBN 0 580 12006 6 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 British Standard does not of itself confer immunity fr
4、om 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 date) and may have had amendments incorporated. This will be indicated in the amendm
5、ent table on the inside front cover. Amendments issued since publication Amd. No. Date of issue CommentsBS6070-7:1981 BSI 12-1999 i Contents Page 1 Scope 1 2 Reference 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Procedure 1 7 Expression of results 2 Table 1 Volumes of standard copper solution 1 Pub
6、lication referred to Inside back coverii blankBS6070-7:1981 BSI 12-1999 1 1 Scope This Part of BS6070 describes a method for the determination of the copper content of sodium carbonate for industrial use. The method is applicable to products having copper contents, expressed as Cu, in the range0.5mg
7、/kg to10mg/kg. There is no International Standard corresponding to this Part of BS6070. 2 Reference The title of the publication referred to in this standard is given on the inside back cover. 3 Principle The copper present is reduced with ascorbic acid and a violet coloured complex is formed by add
8、ition of 2,2-biquinolyl. This complex is extracted with amyl alcohol and its colour measured spectrophotometrically. 4 Reagents The following reagents are required and shall be of recognized analytical quality. Water complying with the requirements of BS3978 shall be used throughout. 4.1 Sodium sulp
9、hate, anhydrous. 4.2 Hydrochloric acid solution, approximately1.18g/ml, approximately36% m/m solution or approximately11N. 4.3 Amyl alcohol 4.4 (+)-Tartaric acid, 500g/l solution. 4.5 Sodium hydroxide, 200g/l solution. 4.6 L-Ascorbic acid, 100g/l solution, freshly prepared. 4.7 2,2Biquinolyl, 0.5g/l
10、 solution. Dissolve0.25g of2,2biquinolyl in the amyl alcohol (4.3) and dilute with more of the amyl alcohol to500ml. 4.8 Bromine water, saturated solution. 4.9 Copper, standard solution corresponding to0.1g of copper per litre. Dissolve0.3928g of copper (II) sulphate pentahydrate (CuSO 4 .5H 2 O) in
11、 water in a1000ml one-mark volumetric flask, add25ml of approximately6N sulphuric acid solution, dilute to the mark and mix. 1 ml of this standard solution contains 0.100mg ofCu. 4.10 Copper, standard solution corresponding to0.01g of copper per litre. Dilute10.0ml of the standard copper solution (4
12、.9) to the mark in a100ml one-mark volumetric flask and mix. 1 ml of this standard solution contains104g of Cu. 4.11 Narrow range indicator papers, covering the range pH5.5 to pH7.0. 4.12 Methyl orange indicator, 0.5g/l aqueous solution. 5 Apparatus Ordinary laboratory apparatus and the following ar
13、e required. 5.1 Spectrophotometer, or 5.2 Photoelectric absorptiometer, fitted with filters providing maximum transmission at a wavelength of about545nm. 5.3 Optical cells, 4cm optical path length. 6 Procedure 6.1 Test portion. Weigh, to the nearest0.1g, about10g of the sample. 6.2 Blank test. Carry
14、 out a blank test at the same time as the determination, following the same procedure and using the same quantities of reagents as specified in6.3.2 but omitting the test portion. 6.3 Preparation of the calibration graph 6.3.1 Preparation of standard matching solutions Into each of a series of six50
15、0ml stoppered separating funnels introduce the volumes of the standard copper solution (4.10) shown inTable 1. Table 1 Volumes of standard copper solution Standard copper solution (4.10) Corresponding mass of copper (Cu) ml g 0 a 0 2.0 20 4.0 40 6.0 60 8.0 80 10.0 100 a Compensation solutionBS6070-7
16、:1981 2 BSI 12-1999 6.3.2 Colour development. Treat the contents of each funnel (6.3.1) as follows. Dilute with water to approximately400ml, then add2ml of the tartaric acid solution (4.4). Adjust the pH of the solution to about6.0by addition of the sodium hydroxide solution (4.5) using the narrow r
17、ange indicator paper (4.11) externally. Add2ml of the ascorbic acid solution(4.6), shake so as to mix thoroughly and allow to stand for5min. Add10ml of the 2,2-biquinolyl solution (4.7) and shake well for about2min. Extract the copper complex with two20ml portions of the amyl alcohol (4.3), and tran
18、sfer the extracts to a100ml beaker. Add about2g of the anhydrous sodium sulphate (4.1) to the combined extracts and stir thoroughly to remove traces of water. Filter the dried extract into a 50ml one-mark volumetric flask, wash the residual sodium sulphate twice with 2ml portions of the amyl alcohol
19、 (4.3). Transfer the washings to the flask, dilute to the mark with the amyl alcohol (4.3) and mix. 6.3.3 Photometric measurements. Carry out the photometric measurements either with the spectrophotometer (5.1) at the wavelength of maximum absorption (about545nm), or with the photoelectric absorptio
20、meter (5.2), fitted with suitable filters, after having adjusted the instrument to zero absorbance against the amyl alcohol (4.3). 6.3.4 Plotting the calibration graph. Deduct the absorbance of the compensation solution (6.3.1) from those of the standard matching solutions(6.3.1). Plot a graph havin
21、g, for example, the copper content, expressed in micrograms per50ml of standard matching solution, as abscissae and the corresponding values of absorbance as ordinates. 6.4 Determination 6.4.1 Preparation of the test solution, Transfer the test portion(6.1) quantitatively to a400ml beaker. Add about
22、100ml of water and one drop of the methyl orange indicator solution (4.12). Neutralize the solution with the hydrochloric acid solution(4.2), then add5ml in excess. Add10ml of the bromine water (4.8) and boil the solution until free from bromine and allow to cool. Transfer the contents of the beaker
23、 quantitatively to a500ml separating funnel fitted with a stopper and add1ml of the hydrochloric acid solution (4.2). 6.4.2 Colour development. Treat the test solution in the separating funnel (6.4.1) as specified in6.3.2. 6.4.3 Photometric measurement. Carry out the photometric measurement on the t
24、est solution(6.4.2) and on the blank test solution (6.2) following the procedure described in6.3.3, after having adjusted the instrument to zero absorbance against the amyl alcohol (4.3). NOTEIf the absorbance exceeds the maximum of the calibration graph, repeat the determination using a smaller amo
25、unt of the test portion (6.1) and modifying the calculation accordingly. 7 Expression of results By means of the calibration graph (6.3.4), determine the quantity of copper (Cu) corresponding to the value of the photometric measurement. The copper content, expressed as milligrams of copper (Cu) per
26、kilogram, is given by the following formula where m 0 is the mass of the test portion (in g); m 1 is the mass of copper in the test solution (in4g); m 2 is the mass of copper in the blank test solution (in 4g).BS6070-7:1981 BSI 12-1999 Publication referred to BS 3978, Water for laboratory use. BS 60
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