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1、BRITISH STANDARD BS 5688-7: 1979 ISO 2215:1972 Methods of Test for Boric acid, boric oxide, disodium tetraborates, sodium perborates and crude sodium borates for industrial use Part 7: Determination of copper content of boric acid, boric oxide and disodium tetraborates ISO title: Boric acid, boric o
2、xide and Disodium tetraborates for industrial use Determination of copper content Zinc dibenzyldithiocarbamate photometric method NOTEIt is recommended that this Part be read in conjunction with the information in the “General introduction”, published separately as BS 5688-0. UDC 661.65:546.273:543.
3、062:546.56 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:50:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5688-7:1979 This British Standard, having been prepared under the direction of the Chemicals Standards Committee, was published under the authority of the Executive Board on 28 Fe
4、bruary 1979 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference CIC/16 Draft for comment 74/53496 DC ISBN 0 580 10540 7 National foreword This Part of BS 5688 is identical with ISO 2215 “Boric acid, boric oxide and Disodium tetraborates for industrial us
5、e Determination of copper content Zinc dibenzyldithiocarbamate photometric method” published by the International Organization for Standardization (ISO). Terminology and conventions. The text of the International Standard has been approved as suitable for publication, without deviation, as a British
6、 Standard. Some terminology and certain conventions are not identical with those used in British Standards; attention is drawn to the following. Where the words “International Standard” appear, referring to this standard, they should be interpreted as “British Standard”. Additional information Water
7、. Water complying with the requirements of clause 3 is specified in BS 3978 “Water for laboratory use”. Reagents. Unless otherwise stated, it is essential that the reagents used in this determination be of recognized analytical grade. WARNING NOTE. Clauses 3.3, 5.3.2 and 5.3.3 require the use of car
8、bon tetrachloride as a solvent. In view of its toxic nature, breathing of the vapour and contact with the skin and eyes should be avoided. All operations involving its use should be carried out in a fume cupboard. A British Standard does not purport to include all the necessary provisions of a contr
9、act. 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 inside front cover, pages i and ii, pages 1 and 2 and a back cover.
10、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 of issueComments Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:50:46 GMT
11、+00:00 2006, Uncontrolled Copy, (c) BSI BS 5688-7:1979 BSI 12-1999i Contents Page National forewordInside front cover 1Scope and field of application1 2Principle1 3Reagents1 4Apparatus1 5Procedure1 6Expression of results2 7Test report2 Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:50:46
12、GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:50:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5688-7:1979 BSI 12-19991 1 Scope and field of application This International Standard specifies a zinc dibenzyldithiocarbamate method for
13、the photometric determination of the copper content of boric acid, boric oxide and disodium tetraborates for industrial use. 2 Principle Formation of a coloured complex between the copper and zinc dibenzyldithiocarbamate and photometric measurement at a wavelength of approximately 435 nm. 3 Reagents
14、 Distilled water or water of equivalent purity shall be used in the test. 3.1 Carbon tetrachloride, redistilled. 3.2 Hydrochloric acid, approximately 6 N solution, freed from copper by extraction with the zinc dibenzyldithiocarbamate solution (3.3). 3.3 Zinc dibenzyldithiocarbamate, 0.5 g/l solution
15、 in carbon tetrachloride. Dissolve 0.05 g of zinc dibenzyldithiocarbamate in the carbon tetrachloride (3.1) and dilute to 100 ml with the same carbon tetrachloride. 3.4 Copper standard solution, containing 0.10 g/l of Cu. Weigh, to the nearest 0.000 1 g, 0.1 g of electrolytic copper and dissolve in
16、10 ml of approximately 8 N nitric acid solution. Heat the solution on a hot plate until the fumes evolved are no longer brown, cool and add about 100 ml of water. Transfer quantitatively to a 1 000 ml one-mark volumetric flask, dilute to the mark and mix. 1 ml of this solution contains 0.10 mg of Cu
17、. 3.5 Copper standard solution, containing 0.010 g/l of Cu. Transfer 10.0 ml of the copper standard solution (3.4) to a 100 ml one-mark volumetric flask, dilute to the mark and mix. 1 ml of this standard solution contains 10 4g of Cu. Prepare this solution just before use. 4 Apparatus Ordinary labor
18、atory apparatus and 4.1 Spectrophotometer, with 4 cm cells, or 4.2 Photoelectric absorptiometer, with 4 cm cells. 5 Procedure 5.1 Test portion Weigh to the nearest 0.1 g, a mass of the test sample as indicated in the following table: 5.2 Blank test At the same time as the analysis, carry out a blank
19、 test using the same procedure and quantities of all reagents employed in the determination. 5.3 Preparation of calibration curve 5.3.1 Preparation of standard colorimetric solutions Into a series of five 250 ml separating funnels, each containing 50 ml of the hydrochloric acid solution (3.2), trans
20、fer the quantities of the copper standard solution (3.5) indicated in the following table: Material Mass, in grams, of test portion boric acid boric oxide disodium tetraborate decahydrate disodium tetraborate pentahydrate anhydrous disodium tetraborate (H3BO3) (B2O3) (Na2B4O710H2O) (Na2B4O75H2O) (Na
21、2B4O7) 10 5 15 10 10 Volume of copper standard solution (3.5) Corresponding mass of copper ml4g 0a 0.5 1.0 1.5 2.0 0 5 10 15 20 a Compensation solution Licensed Copy: sheffieldun sheffieldun, na, Mon Dec 04 15:50:46 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5688-7:1979 2 BSI 12-1999 5.3.2 Develo
22、pment of the colour Dilute the contents of each separating funnel to approximately 200 ml with water and mix. Add 10 ml of the zinc dibenzyldithiocarbamate solution (3.3), shake the funnel vigorously for 1 min, and allow the layers to separate. Run off the lower, organic layer and filter it through
23、a retentive filter paper into a 25 ml one-mark volumetric flask. Treat the aqueous phase with a 10 ml portion of the zinc dibenzyldithiocarbamate solution (3.3) and filter the organic layer into the same flask. Wash the filter paper with the carbon tetrachloride (3.1), adding the washings to the fla
24、sk. Dilute to the mark with the carbon tetrachloride (3.1) and mix. 5.3.3 Photometric measurements Using the spectrophotometer (4.1) at a wavelength of about 435 nm or the photoelectric absorptiometer (4.2) with suitable filters carry out the photometric measurements, adjusting the instrument to zer
25、o absorbance against the carbon tetrachloride (3.1). Deduct the absorbance of the compensation solution from those of the standard colorimetric solutions. 5.3.4 Plotting of the calibration curve Plot a graph having, for example, the quantities in micrograms of copper in 25 ml of the standard colorim
26、etric solution as abscissae and the corresponding values of the abosrbance as ordinates. 5.4 Determination 5.4.1 Preparation of test solution Dissolve the test portion (5.1) in 140 ml of water and add 60 ml of the hydrochloric acid solution (3.2). Simmer the solution for 10 min, cool and transfer qu
27、antitatively to a 250 ml separating funnel. 5.4.2 Development of the colour Develop the colour following the instructions given in 5.3.2. 5.4.3 Photometric measurements Carry out the photometric measurements on the test solution and on the blank solution following the instructions given in 5.3.3, ad
28、justing the instrument to zero absorbance against the carbon tetrachloride (3.1). 6 Expression of results By reference to the calibration curve (see 5.3.4) determine the mass of copper corresponding to the absorbance of the test solution and that of the blank test. The copper content (Cu), expressed
29、 in parts per million by mass, is given by the formula: where mois the mass, in grams, of the test portion; m1is the mass, in micrograms, of copper found in the test solution; m2is the mass, in micrograms, of copper found in the blank test solution. 7 Test report The test report shall include the fo
30、llowing particulars: a) the reference of the method used; b) the results and the method of expression used; c) any unusual features noted during the determination; d) any operation not included in this International Standard or regarded as optional. m1m2 m0 - - Licensed Copy: sheffieldun sheffieldun
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